StimGun book cover 9/18/02 12:32 PM Page 2

StimGun

StimGun
Technology
A complete guide to the

StimGun assembly,
StimGun Technology

StimTube tool, and

Well Stimulation tool

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Ta b l e o f C o n t e n t s

StimGun
Table of Contents
Editors Notes
4 Janet Emr, Marathon Oil Company
StimGun
Introduction
The Propellant Technology Development
5 Group and the licensees

Introduction to the StimGun family

StimGun Technology is a
publication of the Propellant 7 of products
Technology Development
Group:
Tools, components and industry usage
Computalog Wireline Services,
Precision Drilling Technology
8 Brent Kirschner, Owen Oil Tools
Services Group, Inc.
Safety and regulatory compliance
HTH Technical Services, Inc. 12 David Boston, Owen Compliance Services, Inc.
Instrumentation & Engineering Joe Haney, HTH Technical Services, Inc.
Services, Inc.
Marathon Oil Company Background
Owen Oil Tools
Historical and technical perspectives
15 Joe Haney, HTH Technical Services, Inc.
John Schatz, John F. Schatz Research & Consulting, Inc.

Demonstration of pressure wave motion in the

20 well caused by a dynamic event
John Schatz, John F. Schatz Research & Consulting, Inc.

Effective penetration is enhanced by the

24 StimGun assembly
Dan Pratt, Owen Oil Tools

Propellants can break through formation

This publication is provided for informa-
tional purposes only. The recipient of this pub-
lication assumes full responsibility for deter-
25 damage created by perforating
mining whether the information contained James Barker, Jet Research Center, a division of Halliburton Energy
herein is appropriate for its use.
Services
Neither the companies represented by the
Propellant Technology Development Group John Hardesty, Jet Research Center, a division of Halliburton Energy
nor any person acting on their behalf:
Services
a. Makes any warranty or representation,
express or implied, with respect to the Phil Snider, Marathon Oil Company
accuracy, completeness, or usefulness
of the information contained in this
A nodal analysis of why near-wellbore
publication; or
b. Assumes any liability with respect to the
use of, or for damages resulting from
29 fracturing with propellant increases
the use of, any of this information; or productivity
c. Gives any warranties; all implied
warranties or merchantability or fitness
John Gilbert, Marathon Oil Company
for a particular purpose are expressly Craig Beveridge, Owen Oil Tools
excluded.
The information contained herein is
intended as a general illustration of the possi- Products & Applications Overview
ble applications of the StimGun tools and
technology described herein. The companies
Product testing to develop and confirm tool
represented by the Propellant Technology
Development Group specifically disclaims any
warranties, expressed or implied, with respect
33 performance
to suitability of a particular product as a solu- Joe Haney, HTH Technical Services, Inc.
tion to a specific problem or condition.
Bob Daly, Marathon Oil Company

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Candidate well selection for the StimGun assembly technology

35 Bob Haney, HTH Technical Services, Inc.

When StimGun products may be the wrong choice

37 Joe Haney, HTH Technical Services, Inc.

Choosing the right tool and conveyance method

39 Phil Snider, Marathon Oil Company

Pre-job planning
42 David Cuthill, Computalog Wireline Services
Bob Haney, HTH Technical Services, Inc.

PulsFrac software: How does it work? What does it do?

44 John Schatz, John F. Schatz Research & Consulting, Inc.

IES high-speed/high-shock downhole memory gauge

46 Scott Ager, Instrumentation & Engineering Services, Inc.

PulsFrac software and IES high-speed memory gauges used to design

50 and confirm propellant behavior, perforation breakdown,
and formation fracturing
John Schatz, John F. Schatz Research & Consulting, Inc.
Bob Haney, HTH Technical Services, Inc.
Scott Ager, Instrumentation & Engineering Services, Inc.

Big-block surface test of the StimGun assembly

56 Brent Kirschner, Owen Oil Tools
John Schatz, John F. Schatz Research & Consulting, Inc.

Using the IES high-speed gauge in TCP drop bar applications

59 Casey Weldon, Baker Atlas
Alphie Wright, Baker Atlas

Application Type: Perforation Breakdown

An interview with Buddy Woodroof, ProTechnics Technical Manager
63 Paul Gardner, Marathon Oil Company

Does propellant help or hurt hydraulic fracturing?

65 E. Glynn Williams, Marathon Oil Company

An overview of SPE paper 63104: New techniques for hydraulic fracturing in

67 the Hassi Messaoud Field
Kent Folse, Halliburton Energy Services

Improving hydraulic fracturing effectiveness by wireline StimGun assembly

68 perforating in the San Andres Formation of West Texas
Kevin Miller, Marathon Oil Company

Underbalanced TCP StimGun assembly applications to obtain

74 initial production and improve hydraulic fracturing
Jim Gilliat, Canadian Completion Services The Expro Group

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Ta b l e o f C o n t e n t s

StimGun
An overview of SPE paper 71639: Field performance of
77 propellant/perforation technologies to enhance placement of proppant
on high-risk sand-control completions
Kent Folse, Halliburton Energy Services

Propellant assisted perforation breakdown examples

78 David Cuthill, Computalog Wireline Services

Restoring injectivity
83 Bob Haney, HTH Technical Services, Inc.

Application Type: Near-Wellbore Stimulation

The first applications of TCP underbalanced propellant jobs in shallow
87 Rocky Mountain gas wells
Ralph Affinito, Marathon Oil Company
Larry Staten, Halliburton Energy Services

High-speed gauge data improves job success on wireline-conveyed

89 near-wellbore stimulations
Todd McAleese, Marathon Canada, Ltd.

Combining StimGun assembly with EOB perforation and acid

91 stimulation significantly improves New York states gas production
Craig Smith, The Expro Group (formerly with Halliburton Energy Services)

An overview of SPE paper 68101: A unique approach to enhancing

92 production from depleted, highly laminated sand reservoirs using
a combined propellant/perforating technique
Kim Hungerford, Halliburton Energy Services

Successfully combining the StimGun assembly with

93 Pow*rPerf technologies
Frank Oriold, Canadian Completion Services The Expro Group

Slickline-conveyed StimTube tool stimulation: an alternative to

95 a high-rate acid fracture
Bill Barton, Tripoint, Inc. The Expro Group

Propellants have dramatically increased production from heavy oil wells:

96 the need for hydraulic fracturing has been reduced
Kevin Newmiller, Precision Drilling
Perry Huber, Plains Perforating Ltd.

Enhancing sand/oil production in the Lloydminster Canada area

101 David Cuthill, Computalog Wireline Services
Lane Merta, Computalog Wireline Services

Stimulation of shallow gas wells

106 David Cuthill, Computalog Wireline Services

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Application Type: Open Hole Stimulations

Open hole completions: case histories and technical studies with formation
111 micro imaging (FMI)
Brent Kirschner, Owen Oil Tools

General Interest and Whats Next

Myths and misconceptions
117 John Schatz, John F. Schatz Research & Consulting, Inc.

Benefits of using high-speed gauge data to obtain rock properties

122 John Gilbert, Marathon Oil Company
John Schatz, John F. Schatz Research & Consulting, Inc.
David Cuthill, Computalog Wireline Services
Bob Haney, HTH Technical Services, Inc.

New product and technology development

124 John Schatz, John F. Schatz Research & Consulting, Inc.
Joe Haney, HTH Technical Services, Inc.

Appendix
127 Glossary
133 Reference list
137 Contributing authors biographies
149 Selected SPE papers

Editors Notes Janet Emr, Marathon Oil Company

and did a great job of executing early field work.

E diting the StimGun Technology book was a daunt-
ing task, but I am grateful for the opportunity to
work with such experienced and highly knowledge-
Doug Robinson and Mike Boyle, as early strong
supporters of propellant technology with vision.
able individuals. I feel privileged to be a part of the
Propellant Technology Development Group and for Craig Dickerson continues to be key member of
having the opportunity to gain knowledge from it. I the group and also deserves recognition. Craig's
would like to express my gratitude to Cindy Guire for practicality combined with his enthusiasm enables
her patience and perseverance working countless continued manufacturing process improvement
hours with me on the layout and graphic work. and quality control.
Although they do not appear here as contributors, The reader should find this book a valuable
the Propellant Group wishes to recognize several indi- resource for understanding and applying StimGun
viduals contribution during the early development propellant* technology. Please contact the Propellant
stage of the technology. Some of these individuals have Technology Development Group if clarification or fur-
moved to other companies or occupations, but we ther information is needed. Contact information for
continue to consider them valued friends and partners. the members of the Propellant Technology
David Wesson, formerly of Owen Oil Tools, had Development Group is included in the Appendix
the energy and ideas that became infectious, along with the Contributing Authors Biographies.
making the project fun.
David Carlson and J.C. Picard, formerly with * The StimGun family of products are DOT classified a oxidizers
Computalog Wireline Services, spent countless (5.1) and not as propellants. For classification purposes, propel-
lants are equivalent of explosives. Therefore throughout this pub-
hours driving between Edmonton, Canada and lication, when the term propellant is used with regard to
Cody, Wyoming to perform the first evaluations of StimGun products, it should technically be interpreted in DOT
the technology. They believed in the technology terms to mean oxidizer, mixture, solid.

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I n t r o d u c t i o n

The Propellant Technology

Development Group and the
licensees
Eight individuals with 12 plus years of
T he Propellant Technology Development
Groups goal is to integrate the perforation,
well stimulation, well production, computer model-
propellant manufacturing/operations
experience
ing, and high-speed data collection technologies. Completion engineers with over 20 years of
Each of the individual companies had been work- experience
ing on components of the technology, and when
Shaped charge design engineers with 30 years
Marathon Oil Company took the lead in forming
the group, the joint expertise and resources proved of experience
successful in developing this technology. Geophysicist with a PhD in rock mechanics
Propellant Technology Development Group per- from MIT with 35 years of experience
sonnel represent a broad base of knowledge, expe- Individuals assisting the United Nations
rience, and expertise. The group has access to the explosives shipping and testing organizations
combined resources of the individual participating Over 50 combined years of military experience
companies. in high-shock measurements
The groups credentials include individuals with: Total of over 300 years of oil field experience for
Over 20 mechanical oilfield tool patents the core team members

Marathon Oil Company HTH Technical Services, Inc.

Test Wells, Producing Wells Propellant Manufacturing
Perforating, Completion Expertise Propellant Field Experience
Legal/Patent Expertise Recorder Field Experience

John F. Schatz
Owen Oil Tools Research & Consulting, Inc.
Shaped Charge Manufacturing
Hardware Manufacturing Computer Simulation Expertise
Shipping/Distribution Rock Mechanics Expertise
Design Expertise Propellant Design Experience

Instrumentation and
Engineering Services Computalog
High Speed Recorder Wireline Service Company
Hardware Manufacturing Propellant Field Experience
Shipping/Distribution
Design Expertise

Propellant Technology Development Group companies and their resources.

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Licensees of the StimGun assembly and

related technologies
There are at least nine companies licensed with the
StimGun assembly and related technologies. These
licenses range from worldwide tubing-conveyed per-
foration (TCP) and wireline with integrated major
service companies to single country wireline licenses.
The Propellant Technology Development Group
views its association with its licensees as a team effort.
This approach has resulted in the rapid development
and worldwide commercialization of the StimGun
technology while minimizing the past reputation of
propellant stimulation products for misapplication,
misuse, and poor design.
License agreements for the StimGun body of tech-
nology are available from the Propellant Technology
Development Group through Marathon Oil
Company.

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I n t r o d u c t i o n

StimGun

Introduction to the StimGun

family of products
evaluated, the applicability of the technology has
I n the right application and with the right tool,
propellants work. However, all propellant-based
products are not the same. The StimGun family of
been assessed, potential problems have been mini-
mized, and when complete, results can be quanti-
propellant-based products offers the industry the tatively evaluated.
first fully integrated, technology-based, and thor-
oughly tested tools designed to dynamically clean Perhaps the easiest way for us to introduce the
up and stimulate the near-wellbore area. These technology is to review a few of our successes.
stimulations are not only cost-effective, but in The remainder of articles in this publication pres-
many instances may be the only available solution ent in detail the who, why, and how of the
for elimination of certain near-wellbore problems. StimGun family of products.
This technology is used both as a primary stimula-
tion and in conjunction with other stimulation The StimGun assembly received Harts
technologies such as hydraulic fracturing. Petroleum Engineering International
To date, several thousand wells have been suc- Special Meritorious Engineering Award for
cessfully treated. The key to our success has been Engineering Innovation. The Propellant
in development of an engineered process for Development Technology Group was hon-
the optimization of stimulation design. The ored to receive this prestigious award at the
process integrates computer modeling, high-speed Offshore Technology Conference in 1997. The entry was
data acquisition, testing, and data interpretation. submitted in the Completions and Perforating category
The result is the ability to select propellant tools and was recognized as one of the years best new engineer-
and treatment procedures that ensure the cus- ing innovations in the industrys efforts to improve well
tomer that each specific job has been thoroughly completions.

StimGun Assembly StimTube Tool Well Stimulation Tool (WST)

Problem: Hydraulic Problem: Well was Problem: Operator was

fractures had perforated, but did unable to initiate
inefficient not flow. hydraulic fracture
proppant treatment due to a
placement. lack of breakdown

Location: West Texas Location: Gulf of Thailand Location: Western Canada

Solution: Perforate with Solution: Treat with 5 ft Solution: Treat with 6 ft (2 m)

StimGun (1.5 m) StimTube WST centered on
assembly tool centered on 10 ft (3 m) perforat-
11 ft (3.3 m) ed interval
perforated interval.

Results: Proppant was Result: The well flowed at Result: Hydraulic fracture
placed over the 1 mmcf/day initiated and went
entire zone, as veri- (30 E3m3/d). away successfully
fied by radioactive with no discernible
tracer analysis. breakdown
pressure.

Examples of case history successes for perforation breakdown and near-wellbore stimulation.

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Tools, components, and industry

usage
Brent Kirschner, Owen Oil Tools

T he StimGun family of products currently consists

of three unique tool configurations the
StimGun assembly, the StimTube tool and the Well
The StimGun technology is best understood as an
engineered job design process that integrates the use
of the products with PulsFrac computer modeling and
Stimulation Tool (WST). These three products allow data acquisition using the high-speed gauge. Unlike
for maximum stimulation design flexibility for a wide approaches used by others, the StimGun technology
range of well configurations. With each of these prod- takes into account well fluids, well mechanicals, and
ucts, production/injection enhancement is accom- rock properties to select the optimum tool for each
plished through perforation breakdown and near- specific application.
wellbore stimulation.

StimGun family of products

StimGun assembly

StimTube tool

Well stimulation tool (WST) and hardware

High-speed/high-shock downhole memory gauge

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I n t r o d u c t i o n

StimGun
The StimGun assembly

perforating gun systems from 2 8 in. (60.3 mm)
3

The StimGun assembly has two major compo- through 7 in. (177.8 mm) outer diameter (OD).
The StimGun assembly can be lowered into the
nents a conventional hollow steel perforating gun
well on wireline, tubing or drill pipe, or with coiled
and a sleeve of special propellant material sur-
tubing.
rounding the gun. The perforating gun is fired in
the wellbore as normal, and as a result of the per- Industry Usage
forating process the sleeve is ignited. The sleeve, As of December 2001, over 30,000 ft (9140 m)
which is a proprietary oxidizer, and binder combi- of the StimGun assembly have been run. This rep-
nation burns quickly and produces a burst of high- resents thousands of successful completions. These
pressure gas. This high-pressure gas enters the per- include onshore-offshore oil, gas, and injector wells
foration and creates fractures resulting in an around the world. The StimGun assembly is a
improved flow path from the formation to the well- field-proven method of perforating and stimulating
bore. The sleeves are available for hollow carrier in one run.

StimGun assembly components

Propellant sleeve Cast tube of a proprietary oxidizer/resin binder material, similar in appearance to plastic pipe, that
simply slides over the perforating guns. The propellant-like material (actually classified as an oxidizer) is ignited by the per-
forating events. Usually a minimum of four shots per foot is required to adequately ignite the sleeve. However, 6 spf (20 spm)
are generally recommended. Maximum temperature rating is 330F (160C). The sleeves are impervious to all current well
fluids.

Centralizing rings Used to position and secure the sleeves to the outside of the perfo-
rating gun. In addition to securing the sleeves, the rings are available over-sized (typically
sleeve OD + 14"/6.4 mm) to protect the sleeves from contact with the casing.

Finned tandem/bull nose subs Subs centralize

the assembly and protect the sleeves while resulting
in minimum flow restriction. Typically gun OD + 12"
(12.7 mm)

Perforating guns Typically hollow steel carrier guns are recommended. Sleeves are currently available for the follow-
ing gun OD sizes: 238", 212", 234", 278", 318", 338, 4", 412", 458", 518", & 7" (60.3 mm, 63.5 mm, 69.9 mm, 73 mm,
79.4 mm, 85.7 mm, 101.6 mm, 130.2 mm & 177.8 mm).

High-speed/high-shock downhole memory gauge Data acquisition at rates up to 100,000 points per second
(user programmable for high, intermediate, and low speeds). Sensors available include pressure, temperature, acceleration
high-G for shock measurement and acceleration, low-G for tool velocity calculation. Maximum memory = one million
data points. Sizes available (OD) = 11116" & 2" (42.9 mm & 50.8 mm). Maximum temperature rate = 255F (125C).

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The StimTube tool cord is then initiated causing the oxidizer to ignite.
The StimTube tool consists of a molded cylinder of Similar to the StimGun, the StimTubes proprietary
propellant-like oxidizing material surrounding an propellant burns quickly and produces a burst of
internal steel support tube containing detonating high-pressure gas.
cord. The StimTube tool provides efficient, cost
Industry Usage
effective remediation to existing perforated or open-
hole intervals. The StimTube tool is available in a As of December 2001, over 12,000 ft (3660 m) of
variety of sizes including 112 in., 11116 in., 2 in., 212 in., the StimTube assembly have been run. Applications
and 3 in. (38.1 mm, 42.9 mm, 50.8 mm, 63.5 mm are primarily through-tubing pre-hydraulic fracture
and 76.2 mm). The StimTube tool is run into the treatment and stimulation of damaged wells, where
wellbore, typically on wireline, and positioned across wellbore restrictions do not allow for the use of the
existing perforations. The conventional detonating StimGun assembly.

StimTube tool components

The StimTube A cast cylindrical rod of proprietary oxidizer/resin material with an embedded steel support tube, ignited
with 40 grain detonating cord. Available sizes Outside Diameters 112", 11116", 2", 212", and 3" (38.1 mm, 42.9 mm, 50.8
mm and 76.2 mm); lengths 1', 2', 3', and 4' (.3 m, .6 m, .9 m and 1.2 m). Maximum temperature rating = 340F (170C).
Impervious to all well fluids.

Firing head Used to connect the detonator to the detonating cord and to connect the tools to the wireline or coiled tubing.

Connecting subs Used to assemble multiple StimTube tools and to minimize tool contact with the casing. Generally,
maximum recommended total length per run of StimTube tool for wireline applications is 15' (4.6 m). Longer lengths can be
run on continuous tubing.

Bull nose sub Used to terminate the assembly and protect the propellant and detonating cord end seal.

High-speed/high-shock downhole memory gauge Typically run just below the wireline cable head.

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I n t r o d u c t i o n

StimGun
Well Stimulation Tool (WST) Industry Usage
The WST is a stick tool consisting of a cast cylin- As of December 2001, over 15,000 ft (4570 m)
drical rod of a proprietary oxidizer/resin material of the WST has been run. This product has an
with a central ignition system. It is primarily used in extremely reliable ignition system and a verified
perforated or open hole wells with no inner diame- burn repeatability. The WST is primarily used as a
ter restrictions. perforation breakdown tool and as a horizontal
well stimulation tool.

Well Stimulation Tool components

End view

WST available sizes ODs 112", 11116", 2 in., 212 in., and 3 in. (38.1 mm, 42.9 mm, 50.8 mm, 63.5 mm and
76.2 mm); lengths 1', 2 ft, 3 ft, and 4 ft (.3 m, .6 m, .9 m and 1.2 m). It is ignited with 40, 60, or 80 grain detonat-
ing cord, however 40 is typically recommended. Maximum temperature rating 250F (120C). Impervious to all well
fluids except methanol.

Steel carriers Similar to a spent perforating gun except with typically 24-1" holes per foot. It is available in
several ODs depending the specific WST used.

Connecting subs Used to assembly multiple WSTs. Generally, maximum recommended total length per run of WST
for wire line applications is 12 ft (3.7 m). Lengths of over 1000 ft (305 m) can run on tubing.

Bull nose sub Used to terminate the assembly.

Firing head Used to connect the detonator to the detonating cord, and to connect the tools to the wire line or tubing.

High-speed/high-shock downhole memory gauge Typically connected below the bull nose sub.

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Safety and regulatory compliance

David Boston, Owen Compliance Services, Inc.
Joe Haney, HTH Technical Services, Inc.

P roduct safety and regulatory com-

pliance are of paramount impor-
tance to the Propellant Technology
Development Group. The StimGun
family of products have all been thor-
oughly tested to ensure that they are
manufactured, transported, stored,
and handled in a manner that meets
worldwide regulatory requirements
and does not endanger people, prop-
erty, or the environment.
Beginning in the product design
phase, issues of product safety and risk
management were addressed. The
chemical oxidizer used in these prod-
ucts was selected based on low sensi-
tivity, high stability, and good per-
formance. The binder used was select-
Figure 1 Surface Test StimGun assembly, 27 in. (73 mm) Perforating Gun,
8
ed based on chemical compatibility, 6 spf (20 spm), no ignition of StimGun sleeve observed.
stability, and fuel content. Prior to start-
up of manufacturing, a preliminary intrinsic hazards for handling of the products by the
hazard assessment was completed. Additionally, the end-user.
products have been tested and classified per UN
Testing and classification of StimGun
Model Regulations and the US Department of
products
Transportation (DOT) regulations. The chemical com-
patibility of the propellant with various well fluids was The testing of the StimGun product family has been
ongoing since 1996. Owen Compliance Services, Inc.
(OCS) performed a hazard assessment review and wit-
products have been nessed the initial product testing. Based on this initial
testing, the products were classified as oxidizers.* This
tested and classified per product classification was later reconfirmed by testing
UN Model Regulations conducted by Natural Resources Canada (NRC),
through its Canadian Explosives Research Laboratory
and the US Department (CERL).
of Transportation (DOT) Additional product safety testing
regulations Owen Oil Tools Inc. has conducted several explo-
sive tests on the products, as follows.
evaluated as well as the effect of rapid low-to-high StimGun assembly
pressure cycling. As part of the risk management Multiple surface tests were performed. An example
assessment, all products were tested for ignition is shown in Figure 1. The most important result is that
potential at surface conditions. The results of the test- perforating guns will not ignite the StimGun assem-
ing have also been used to identify any possible bly sleeves at the surface.
* The StimGun family of products are DOT classified as oxidizers (5.1) and not as propellants. For classification purposes, propellants are
equivalent of explosives. Therefore throughout this publication, when the term propellant is used with regard to StimGun products, it
should technically be interpreted in DOT terms to mean oxidizer, mixture, solid.

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I n t r o d u c t i o n

a b

Figure 2 (a) View of the StimTube tool after detonating cord wrapped around the exterior of the tool was ignited
note that essentially none of the tool was ignited by the detonating cord. (b) View of the StimTube tool after detonating
cord was run through the central ignition tube and ignited. The ignition of the detonating cord resulted in fragmentation
of the tool and minor ignition of some of the fragments.

StimTube tool and all StimTube tools indicated no reaction with

Multiple surface tests were conducted. hydrochloric acid, nitric acid, xylene, and alcohol.
Detonating cord wrapped around the StimTube Mixtures used in the WST and certain obsolete
tool will not ignite the oxidizer material (Figure 2a). StimGun assemblies are affected by water or alco-
Detonating cord run through the full length of the hol absorption.
central igniter tube will fragment and only partially Conclusions
ignite the oxidizer mixture (Figure 2b).
The hazard assessment testing for the UN and
Well Stimulation Tool
DOT classification and for product safety of the
At surface, without confining pressure, detonat- StimGun family of products has been rigorous.
ing cord will not ignite the oxidizer mixture. These products can be safely transported with all
Additional tests of propellant mixtures domestic and international transport regulations.
A harsh environment test at 20,000 psi Guidelines for safe handling and use have been
(138 MPa) and 400F (204C) generated no reac- established. Sensitivities have been determined.
tion. Multiple rapid pressure cycling tests from As with all dangerous goods, there is a potential
atmospheric to 5000 psi (35 MPa) and back gener- for error and/or abuse. Training is required for all
ated no reaction. Fluid compatibility tests with pro- personnel involved with the manufacture, trans-
pellant mixtures used in the StimGun assemblies portation, storage, and end use of the products.

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Nitroglycerin and other

explosives came into general
use as stimulants in 1867 and
prevailed until the late 1940s
when explosive-based
stimulation was replaced by
hydraulic fracturing.
StimGun sect 3 bkgrd 9/19/02 8:31 PM Page 15

B a c k g r o u n d

Historical and technical perspectives

Joe Haney, HTH Technical Services, Inc.
John Schatz, John F. Schatz Research & Consulting, Inc.

R apid energy-release stimulation of oil and gas

wells commenced nearly 150 years ago. In
1860, a black powder torpedo, a 3 ft (0.9 m)
Well Stimulation Tool (WST)
The WST is used primarily to stimulate: perforat-
ed cased intervals, open hole and long intervals in
length of 2 in. (50.8 mm) copper tubing filled with horizontal wells. It is a cast cylindrical rod of pro-
rifle powder, was first used successfully to stimulate pellant with a full length central ignition system.
an oil well. The ignition system has been improved to increase
Nitroglycerin and other explosives came into the tools reliability, burn rate, and reproducibility.
general use as stimulants in 1867 and prevailed Although these steps have enhanced WST per-
until the late 1940s when explosive-based stimula- formance and reliability, its use is somewhat limit-
tion was replaced by hydraulic fracturing. ed by its design.
Solid propellants were introduced in the 1970s In cased wells, the interval must be perforated
and are the basis of modern propellant technolo- prior to running the WST. This two-run require-
gy for oil field use. The performance and success ment is less economical and not always physically
rate of the initially slow burning cylindrical tool possible. Another consideration is that the tool
with a top-to-bottom ignition system was an must be depth-correlated with the existing perfo-
improvement but still marginal by todays stan- rations. This is rarely a problem, but warrants
dards and requirements. In successive years, con- mentioning.
siderable research, development, improved engi- The WST requires an external steel, supporting
neering design, and testing have been applied to carrier similar in appearance to a perforating gun.
solid propellant technology in order to enhance The carriers outside diameter sometimes prevents
its stimulation effectiveness. WST use in wells with inside diameter restrictions.
The latest steps forward, enabled by the com- Nevertheless, the WST remains an attractive
mercialization of high-speed downhole data choice for many previously perforated wells and
recorders, more sophisticated computer modeling, open hole intervals.
and newer tool designs, have been made by the
Propellant Technology Development Group. This StimGun assembly
recent work has resulted in three distinct tool The WST two-run requirement, mentioned
designs now available and in use: above, pointed out the need for a combined perfo-
Well Stimulation Tool rating gun/propellant stimulation tool and prompt-
ed the formation of the Propellant Technology
StimGun assembly
Development Group. In 1996, this group proposed
StimTube tool a new design comprised of a propellant sleeve
placed over the outside of the perforating gun. The
The successes of modern
propellant sleeve is ignited by the perforating
oil-field propellant technology
charge; as the propellant sleeve burns energetic
developed by this group are due to: gases are released.
An integrated science and engineering The group conducted extensive field tests of dif-
package
ferent sleeve designs to optimize the ignition and
New propellant tool designs burn rate of this new StimGun assembly. The col-
High-speed data acquisition lection and interpretation of the down-hole, high-
Computer modeling speed pressure data were essential in the optimiza-
tion. Computer modeling demonstrated that com-
Data analysis and job optimization
bining propellant stimulation with the perforating
Extensive field experience
in one run resulted in a more efficient stimulation

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StimGun sect 3 bkgrd 9/19/02 8:31 PM Page 16

as compared to the two-run perforating gun/WST liquid in the well to penetrate the perforations (perfs)
combination. This new design was subsequently and cause breakdown with fracture propagation into
patented, trademarked, and is now in worldwide com- the formation. It also causes the liquid to compress
mercial use. and move upward and downward in the well.

StimTube tool Perforation breakdown and tortuosity

When run without its required protective steel carrier, reduction
the WST failure rate is unacceptably high because of its Perforating guns release energy in microseconds
mechanical weakness. Work to strengthen the WST led (1/1,000,000 of a second), the gas energy from pro-
to the concept and testing of a tool with an endoskele- pellant burn releases in tens to hundreds of a millisec-
ton, or central steel mini-perforated strengthening tube onds (1/1000 of a second), and hydraulic fracturing
which also contains the igniter. This design together stimulations expend energy over many minutes. A pro-
with a modified propellant type increases the maxi- pellant is therefore intermediate to the other meth-
mum temperature rating and enhances the burn rate. ods in its energy release rate.
In addition to through-tube applications, the Figure 2 (a, b, c) shows laboratory test results and
StimTube tool, because of reduced equipment require- typical pressure-time records for (a) explosive events,
ments, is an excellent replacement for the WST for full (b) propellant events, (c) hydraulic fracture events.
inner diameter (ID), cased well stimulations. Explosive events, such as perforating, create very
The StimTube tool, both patented and trademarked, high pressures, necessary to penetrate the well
is the Propellant Technology Development Groups casing, that also crush and damage the rock.
newest product, and has shown good success since its Propellant events rapidly exceed the fracture
introduction. pressure of the rock and maintain the pressure but
Propellant stimulation technology and do not crush the rock.
dynamic fracturing Hydraulic fracture events balance the driving
The burn of a propellant in a well is a rapid oxida- pressure and the fracture pressure.
tion reaction causing the release of gaseous energy as As a result, propellants pressurize and break down
shown in Figure 1. This gaseous energy mixes with the many perforations along a significant proportion of
their length; while a hydraulic fracture, entering only
the path energetically allowed, breaks down only a
small subset of perforations. These breakdowns may
Wellbore
Tamping interior be very near to the sand face or in a micro annulus.
liquid
Fracture propagation and orientation
Fluid motion
Expanding in well Propellant-driven fractures originating at the perfo-
gasified
bubble
ration tunnels will then move (propagate) into the
formation from a few feet to a few tens of feet, as
Propellant shown schematically in Figure 1 and in the scaled lab-
energy Flow through
source perforations and oratory simulation of Figure 3. The high pressure
into fracture
gas/fluid pulse generated by the burning of the pro-
(Two fractures pellant temporarily creates local stress concentrations
shown)
High-speed that are two to three times the normal fracture gradi-
recorder
ent. These stresses are oriented on a plane through
the axis of the wellbore/perforation tunnels.
Propellant-driven fractures will always tend to initiate
in the plane of the axis of the wellbore. This is true
whether the well is vertical or deviated, no matter
what the depth of the well. Contrarily, hydraulic frac-
tures only will initiate in the in-situ stress preferred
Figure 1 Representation of the release of gaseous propel-
lant energy and its exit from the wellbore into the formation. plane in deeper vertical wells (Figure 5a). For wells in
the depth range of 500 to 2000 ft (152 to 609.6 m)

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B a c k g r o u n d

Explosive event

~>105 psi
Rock Crushing

P Fracturing

Time Microseconds
(a) Laboratory explosive test Pressure vs. time for typical explosive event.

Propellant event

~>104 psi

P P
Fracturing

Time Milliseconds
(b) Laboratory propellant test. Pressure vs. time for typical propellant event.

Gas/liquid event

~>103 psi

Fracturing

Time Seconds
(c) Laboratory hydraulic fracture test. Pressure vs. time for typical hydraulic fracturing.

Figure 2 Laboratory test results and typical pressure-time records for explosive, propellant, and hydraulic fracture
events.

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Figure 3 Propellant stimulation with 90 perforation phasing (Laboratory Scale).

Figure 4 Perforation erosion caused by propellant gas energy (Large Block Surface Test)

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B a c k g r o u n d

(depending on local conditions) and in highly devi- and closure misalignment caused by shear as
ated wells, hydraulic fractures will tend to be out shown in Figure 4 from a surface field test.
of the plane of the wellbore axis (Figure 5b). Although these fractures cannot compete with
Propellant-driven fractures will tend to curve back long propped hydraulic fractures in absolute con-
into the in-situ stress preferred direction, but gen- ductivity values, they can penetrate near-well-
erally propagation is finished before much of the bore damage, reducing skin and mildly stimulat-
curvature occurs. Because late-time propellant- ing wells. They can also act as effective pre-
driven fracture propagation is ultimately controlled hydraulic frac treatments, reducing breakdown
by in-situ stress, the longest propellant fractures pressure and improving proppant placement.
tend to be bi-wings and in the plane nearest the Propellants can be used economically to
in-situ stress preferred plane, although shorter improve well productivity or injectivity. They are
fractures will occur in the other planes. not meant to be replacements for other processes
such as hydraulic fracturing, but they can be
Near-wellbore stimulation excellent solutions or solution enhancements in
Propellant-driven fractures will not contain many situations to perforating limitations, near
proppant in the formal sense, but will retain wellbore damage, or reservoir problems that
some aperture due to erosion, ablation, debris, restrict well potential.

a b

Figure 5 (a) Initial orientation of propellant-driven fractures in all wells and hydraulic fractures in deeper vertical
wells. (b) Orientation of hydraulic fractures in shallower wells and some deviated wells.

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Demonstration of pressure wave

motion in the well caused by a
dynamic event
John Schatz, John F. Schatz Research & Consulting, Inc.

W hen a downhole tool releases a large amount

of energy in milliseconds, pressure waves are
created that travel away from the tool in both direc-
Packer at 7555 ft (2302 m)

Upper Recorder at 7593 ft (2314 m)

tions. Good job design must minimize or control

these waves while still injecting a maximal amount of 3-5/8 in. (92 mm) Tubing
energy into the formation. The tool energy should
breakdown, cleanup, and stimulate and not be wast-
ed in the hole. Unfortunately, it is impossible to com- Middle Recorder at 7797 ft (2376 m)
pletely eliminate these waves when the tool resides Perf Gun/Propellant 7814 to 7828 ft (2382 to 2386 m)
Lower Recorder at 7831 ft (2387 m)
in wellbore fluids, as it must. When the waves are
created, most often they are harmless, but if too 7-5/8 in. (193.7 mm) (6.76/171.7 m ID) Casing
large, they do have the potential to strongly move
the wireline (if used), and adversely affect packers, Plugged at 7960 ft (2426 m)
bridge plugs and other hardware. These waves even-
tually travel to the surface, but are usually not a Figure 1 Simplified schematic diagram of wellbore config-
uration for dynamic reflection example.
problem there. However, for the more shallow wells,
potential impact upon surface equipment must be
considered. In this article, a case study is provided in waves. The upward propagating wave reflects off the
which three recorders were placed in a hole sur- packer and then returns downward. The full com-
rounding a StimGun assembly. The study shows plexity of equipment in the hole is not modeled, so
matching calculations and finally, with the help of some details of the pressure behavior are not cap-
the PulsFrac simulation, shows the progress of the tured. However, all of the main features are easily
waves up and down in the hole, including reflec- identified and calculated.
tions. With knowledge gained in this way, and similar Figure 2 shows measured and calculated pressures
computer runs made for planned jobs, the potential- for the lower gauge (below the source) to a time of
ly adverse effects of pressure waves can be under- 100 ms. Measured peak pressure is about 9000 psi
stood and controlled. (62 MPa), and is matched by calculation. All perfs
break down (not shown). Calculated fracture length
Test results (also not shown) in this soft sand varies from a maxi-
The wellbore configuration for the test is shown in mum of 5.2 ft (1.6 m) in the stress-preferred direction
Figure 1. The source device is a tubing-conveyed to 0.75 ft (0.23 m) in the other. The steep drop to
StimGun assembly containing 10 ft (3.1 m) of pro- below hydrostatic (3500 psi/24 MPa) after ignition
pellant sleeve on a 14 ft by 4.5 in. (4.3 m by 114.3 and the bottomhole reflection at 50 to 60 ms are
mm), 12 spf (39 spm), 30 phased perforating gun. both seen and calculated. The peak magnitude of the
The formation is low-consolidation sand. Three bottomhole reflection is somewhat high. This is com-
downhole recorders are in place. One is below the monly observed and can frequently be accounted for
tool and near to it. One is slightly above the tool, by debris or fluid density or compressibility changes
and one is well above the tool and near to the pack- near the bottom of the hole.
er holding the tubing in place. Calculations have Figure 3 shows measured and calculated pressures
been made to match all of the data obtained. for the middle gauge (above the source). The peaks
The sequence of events starts with the source igni- match. The signal at about 80 ms is the bottomhole
tion followed by upward and downward propagating reflection after it has passed through the gasified,

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B a c k g r o u n d

Figure 2 Measured and calculated pressures for the lower gauge in the dynamic reflection exam-
ple.

Figure 3 Measured and calculated pressures for the middle gauge in the dynamic reflection
example.

Figure 4 Measured and calculated pressures for the upper gauge in the dynamic reflection example.

highly dispersive, and attenuating tool zone. The Wave motion

calculation somewhat overemphasizes these effects, The pressure wave motion triggered by this
smoothing the signal a bit too much. event is shown in the six sequential computational
Figure 4 shows measured and calculated pres- frames of Figure 5. These frames are seen as snap-
sures for the top gauge (near the packer). The dou- shots taken from a movie showing the pressure
ble peak from the incoming and outgoing wave profile in the well from 3 ms until 69 ms. Each
(with respect to the packer) is modeled. The reflect- frame shows pressure vs. depth in the region
ed peak is slightly too small due to small differences between the packer at the top and the plug at the
in dispersion through the reflection zone. bottom. The well must be seen turned on its side.

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Frame (a) shows the pressure immediately after the at a boundary such as the upper packer or the lower
tool ignites. Pressure is approaching its peak and plug. In frame (c), the pressure has momentarily
waves have begun to more upward and downward. grown to about 11,000 psi (76 MPa) at the plug.
Frame (b) shows motion at 15 ms. The downward Although doubling may exceed static packer or plug
wave is slightly stronger than the upward due to the specs, if the pulse is short in duration (in the case
asymmetric top-to-bottom burn of the tool. Frame show less than 10 ms) no physical damage may
(c) shows the peak of the bottomhole reflection. occur. Unfortunately, packers and other downhole
Pressure is nearly doubled, as expected in this type of equipment are not commonly tested and rated for
reflection. Frame (d) shows the reflected wave from dynamic (impulse) loading.
the bottom moving upward, while the original up All of the important wave features are shown in
going wave has not yet reached the packer. Frame (e) this event. If this was a job design calculation, and
shows the top wave striking the packer while the bot- the modeled pressures at critical points, such as the
tom wave has been absorbed by the gasified region at packer, were too high, tool dimensions or other
the gun. Finally, frame (f) shows the reflection from equipment could be modified to maintain pressure at
the packer beginning to move downward. With this an acceptable level while still successfully performing
type of calculation, it is possible to reposition equip- the job. This example demonstrates the potential
ment in the hole and resize tools to consider the importance of pressure waves and how measure-
effect of pressure reflection effects. For example, a ments and calculations can be used to design and
clean reflection will momentarily double the pressure control even the most complex events.

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B a c k g r o u n d

(a) shows the wave structure form-

ing at the end of the perforation
gun burn and the early part of the
propellant burn.

(a) 3 ms
(b) shows the waves moving
upward and downward (left and
right, respectively).

(b) 15 ms
(c) captures the moment when the
downward incident wave strikes
the bottom plug.

(c) 27 ms
(d) shows the reflected wave from
the bottom nearing the tool zone,
while the incident wave is
approaching the upper packer.

(d) 44 ms
(e) shows the reflections at the
upper packer and the gasified tool
zones absorption of the lower
wave.

(e) 61 ms

(f) shows the reflected wave from

the packer at the upper recorder.

(f) 69 ms
Figure 5 Calculated pressure wave structure for dynamic reflection example.

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Effective penetration is enhanced by

the StimGun assembly
Dan Pratt, Owen Oil Tools

tration is only 25% that of concrete. The decrease in

U nder downhole conditions, and especially for
hard rock, actual perforation penetration is less
than published API data. In many instances, shaped
shaped charge jet penetration in hard and/or
stressed formations is generally understood, but far
charge penetration will be less than ten inches in too often ignored. It is a critical aspect of production
hard rock, highly-stressed formations. The current optimization.
standard for testing shaped charges is a Section I API Many literature reports confirm and attempt to
target, as defined by RP 19B. This a man-made, non-
explain this trend of results. Specialized shaped
reactive, material (concrete). Natural rock is a reac-
charges designed for specific hard rock targets can
tive material, in that it does not act linearly to the
likely increase penetration by 10% to 15%, and this
passage of the perforating jet. Rock porosity, grain
is a better approach than designing for optimal con-
size, strength, density, and lack of homogeneity all
crete penetration, but penetrations will still be less
affect the velocity of the jet and therefore affect the
than ordinarily hoped for.
penetration of the jet.
In hard, highly-stressed rock the StimGun assem-
The use of concrete targets is justified by the need
bly can break down perforations and extend frac-
to reduce both cost and variability of test results.
However, results cannot be thought of as definitive tures to a few feet from the wellbore. This may not
for real downhole conditions. As an example of how seem important at first when compared to API con-
shaped charge penetration decreases for real down- crete data, but in reality this can be 500% deeper
hole conditions due to different rock types and for into the formation than the perforating charges
high overburden stress (which are not the only alone might provide. In soft rock under low or inter-
parameters affecting penetration), consider the data mediate stress, where actual penetrations may be
in Table 1. As a basic rule of thumb, when the target closer to API data, StimGun fractures can be more
strength reaches the 12,000 to 15,000 psi (83 to than 10 ft (3 m) in length, still much greater than
103 MPa) level, the penetration will be reduced by perforation penetrations. Although these fractures
approximately half that of the same charge tested in have limited conductivity as compared to hydraulic
concrete. Once the 22,000 to 25,000 psi (151 to fractures, studies have shown that significant flow
172 MPa) level is reached, the penetration again along the fracture plane to the perforation tunnel is
decreases by about half, meaning the actual pene- possible.

Penetration Charge A Charge B Charge C

API Concrete 28.9 in. (734 mm) 27.8 in. (706 mm) 37.4 in. (950 mm)

Berea Sandstone 14.2 in. (361 mm) 14.4 in. (366 mm) 16.9 in. (429 mm)

Nugget Sandstone 11.8 in. (300 mm) 11 in. (280 mm) 14.2 in. (361 mm)

Blue Top Sandstone 6.4 in. (163 mm) 6.8 in. (173 mm) 7.9 in. (201 mm)

Table 1 Comparative data of three different shaped charges shot into separate targets from SPE paper 52203.

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B a c k g r o u n d

Propellants can break through

formation damage created by
perforating
James Barker, Jet Research Center, a division of Halliburton Energy Services
John Hardesty, Jet Research Center, a division of Halliburton Energy Services
Phil Snider, Marathon Oil Company

P erforation of the well casing and its cement

sheath has been effectively and economically
cal energy per unit volume. The pressure related
to this large energy induces liner collapse. It is the
carried out for many years with conical shaped impact pressure of the liner that causes formation
charges releasing large amounts of stored chemi- damage, reducing the permeability. The following

Casing
Carrier Cement
Explosive

Case

Conical
Booster
Liner

Fluid Gap Formation

(a) DP Shape charged perforator (b) DP charge prior to initiation

Jet Penetrates Carrier

Later Stages of Liner Collapse Produce

Liner Collapses to Form Jet Slower-Moving Slug

(c) DP charge at start of initiation (d) DP charge penetrating the carrier

Jet

Stretching Jet Penetrates Formation

with Millions of PSI of Pressure
(e) DP charge perforating jet beginning to extend (f) DP charge penetrating into the formation

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Compacted Zone
(with Damaged Permeability
from Perforating)
Casing Grain Fracturing Zone
Pulverization Zone

Charge and Core Debris

Open Perforation

Cement

Microscopic photograph of undisturbed sand grains prior to Microscopic photograph of damaged sand after perforating.
perforating.

graphic illustrates how a deep penetrating (DP) significant amounts of funding and resources on com-
shaped charge penetrates the wellbore components. bining perforating and flow testing in stressed perme-
On a microscopic basis, the formation materials able core samples. These tests clearly show that
subjected to this very high load and load rate (mil- because a shaped charge penetrates a significant dis-
tance into the formation, it does not mean the entire
lions of psi in microseconds at the jet center) shatter
perforation tunnel will allow fluid flow. Shaped charge
the individual formation sand grains, as well as reduce
design, overburden stress, rock type and permeability,
the cement particles to a very fine powder. This
and underbalance levels all have an impact the effec-
diminished particle size creates a surrounding filter
tive length of the perforation tunnel. It is common for
cake, reducing permeability and inhibiting effective
a perforation that penetrates 15 in. (38 cm) into the
subsequent fluid injection. Because this new filter cake
formation to have only a flow contribution from the
is so compacted, it is not easily removed by flushing first half of the created tunnel. The following three fig-
or underbalanced perforating operations. ures show the same charge design, shot into the same
Shaped charge manufacturing companies, such as formation permeability at underbalanced, overbal-
Halliburtons Jet Research Center are now spending anced, and balanced conditions (Figures 1a, b, c). It

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B a c k g r o u n d

(a) Figure a shows the effective length of the perforation, when a stressed Castlegate sand-
stone core was shot with 3500 psi (22 MPa) overbalance pressure and subsequently flow test-
ed. The effective length of the perforation which would flow was only 5.5 in. (14 cm),
although the perforation penetrated 12 in. (30 cm). In all three examples, the fluid in the
sandstones pore space was odorless mineral spirits and the permeability of the rock is
approximately 1000 md. The decrease in total target penetration of this specific test is also
due to a higher overburden stress.

(b) Figure b shows the effective length of the perforation, when a stressed Castlegate sand-
stone core was shot at balanced conditions and subsequently flow tested. The effective length
of the perforation which would flow was only 7 in. (18 cm), although the perforation pene-
trated 14 in. (35 cm).

(c) Figure c shows the effective length of the perforation, when a stressed Castlegate sandstone
core was shot with 3500 psi (22 MPa) underbalance pressure and subsequently flow tested. The
effective perforation would flow almost its entire length of 15 in. (38 cm). It is important to
note that 3500 psi (22 MPa) underbalance, generally considered an extremely high level, in this
high permeability sandstone with liquid filled pore space, and cannot always be achieved for
operational reasons.
Figure 1 Stressed Castlegate sandstone cores perforated at various pressure differential conditions.

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can clearly be seen that underbalanced conditions can into the wellbore. Many of those individuals intimate-
improve the perforations effective length, but there ly familiar with perforating believe the industry as a
still is a significant length of the perforation tunnel that whole will be moving towards more flow testing work
does not contribute to flow. and tailored perforating charges specifically designed
for the operators formation characteristics, as well as
To solve this problem, the StimGun assembly, and
the use of propellant technology to enhance inflow
its family of products, use a high energy gas pulse,
performance. Operators may very well move away
with a significantly lower pressure loading rate from API charge penetration data and more towards
thousands of psi in milliseconds to break through a focus on perforating for flow. The next article, does
this hard filter cake and create a pathway into the for- an excellent job of showing some of the productivity
mation, enabling further fluid injection or enhancing enhancements which can result in not only improved
the wells inflow performance. The force of the pulse perforating performance, but also using the propel-
also removes materials plugging the perforations and lant to break down the perforations with very short
redistributes them farther into the fractures or back fractures of varying conductivity.

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B a c k g r o u n d

A nodal analysis of why

near-wellbore fracturing with
propellant increases productivity
John Gilbert, Marathon Oil Company
Craig Beveridge, Owen Oil Tools

A fter drilling and casing a

well, a path between the
producing formation and the
wellbore must be estab-
lished. This usually involves
shaped jet perforators.
Unfortunately, high pressure
(millions of psi) required to
perforate the casing dam-
ages the adjacent formation,
reducing permeability.
The amount of damage in
terms of inflow reduction is
related to two main factors:
the thickness of the damage,
and the magnitude of the per-
meability reduction. Studies
have shown that permeability
reduction can be a factor of Photo 1 Microscopic thin section of a clean sand before perforation. Notice the
the virgin formation perme- rounded sand grains, good porosity, and interconnectivity between the pore spaces.
ability. In the crushed zone,
damage can be much greater;
this damage occurs in addi-
tion to drilling fluid damage.
Photos 1 and 2 illustrate
the damage caused by the
perforating process.

Photo 2 Microscopic thin section of same sand after perforating. Notice the
crushing and compacting of sand grains and the loss of interconnectivity.

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Comparing completion techniques Damaged-zone diameter

Openhole
The following reservoir parameters are selected to diameter

model a typical wellbore producing gas.

Perforated Height h 20 ft (6.1 m)
Crushed-zone
diameter
Reservoir Perm k 1 md
Perforation

Damaged Zone Perm kd 0.25 md Perforation

tunnel
diameter
spacing
(dependent on
Perf Crush Zone Perm kc 0.025 md shot density)

Damaged Zone Radius rd 14 in. (356 mm) Perforation

length

Crush Zone Thickness rdp 0.5 in. (12.7 mm)

Perf Tunnel Radius rp 0.19 in. (4.8 mm)
Phase angle
Perforation Length lp 12 in. (305 mm)
Figure 1 McLeods perforation model, inflow predictions.
Wellbore Radius rw 4.25 in. (108 mm)
For the crushed zone parameters, following depth of crushing is typically 0.5 in. (12.7 mm)
McLeods1 model setting the crushed zone perme- around the perforation tunnel. The following cases
ability to 1/10 of the damaged zone permeability are developed to compare the relative performance of
(Figure 1) is followed. McLeod also suggests that the four completion techniques in the same wellbore.

Case 1 Conventional perforation - Ineffective penetration (not reaching

undamaged reservoir)

Sa =
( )()
k
kd
r
-1 ln d
rw

Kc (Crushed)
Sa =
( ) ( )
1
0.25
-1 ln
14
4.25

Sa = +3.6
Kd K

Sdp =
( )( ) ( )
12h
nLp
k k
-
kc kd
r r
ln dpr+ p
p

Sdp =
( )(
12 20
) (1 - 1
120 12 0.025 0.25
ln
0.19+0.5
0.19 )
Drilling Undamaged Sdp = +7.7
Damaged Reservoir
Ineffective penetration S = 3.6 + 7.7 = 11.3

Because the perforator doesnt connect to the undamaged reservoir the skins associated with the undam-
aged and crushed zone are added together. This calculation assumes 6 spf (20 spm) over the entire forma-
tion height making 120 shots in all. The model used to calculate the skin associated with the crushed zone
is sometimes known as the horizontal micro-model from McLeod (1983).
From this analysis a total skin of +11.3 is calculated, +3.6 from the damaged zone around the well and
+7.7 from the crushed zone around the perforations. A nodal analysis is performed to determine the effect
on the performance of the well from the total skin.

1
McLeod, H.O. Jr.: The Effect of Perforating on Well Performance. J. Pet. Tech. (Jan 1983) p. 34-39.

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B a c k g r o u n d

Case 2 Conventional perforation Effective penetration

(reaching undamaged reservoir)

Kc (Crushed)
Sdp =
( )( ) ( )
12h
nLp
k
kc

k
kdp
r r
ln dp + p
rp

Kd K Sdp =
( )(
12 20

Sdp + 5.8
)( 1

1
120 16 0.025 0.25
ln
0.19+0.5
0.19 )
Sdp + 5.8

Drilling Undamaged
Damaged Reservoir
Effective penetration

For the case of a 16 in. (406 mm) penetration, a similar calculation without a damaged zone yields a
skin of +5.8.

Case 3 StimGun application with 5 ft (1.5 m) created fractures

(Infinite conductivity in fracture)
Assuming for this application that the StimGun assembly typ-
ically generates fractures 5 ft (1.5 mm) in length. This tech-
Rwa = 0.5Wf
nique has the benefit of by-passing both the crushed and the
Rwa = 0.55 = 2.5 = 30 inches damaged zones coupled with moderate stimulation from the
produced fractures. The best case scenario involves generating
S = -ln
( ) ( )
Rwa
Rw
= -ln
30
4.25
= -1.95 infinite conductivity fractures. For an infinite conductivity frac-
ture, the apparent wellbore radius can be calculated by
assuming a wellbore radius that is the fracture half length as
described in case 4.
This calculation yields a negative skin of -1.95 with an infinite conductivity fracture. A more realistic
calculation involves assuming a less than perfect conductivity in the generated fractures.

Case 4 StimGun application with 5 ft (1.5 m) created fractures

(Finite conductivity in fractures, 1 md ft )
1 kfwf
FCD = =1
kXf 5
0.1 From Chart
0.051
Rwa
= 0.051
Xf
Rwa/Xf

0.01
Rwa = 0.051Xf

0.001 Rwa = 0.0515 = 3.06 inches

0.0001 1/5
S= -ln ( ) ( )
Rwa
Rw
= -ln 3.06 = +0.33
4.25
0.001 0.01 0.1 1 10 1

The skin is calculated to +.33 with 1 md ft fracture conductivity.

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Nodal analysis comparing the four cases

Nodal analysis, a procedure for determining the conventional completions to StimGun in the follow-
flow rate at which a well will produce, compares ing case results:

5000

4500

4000

3500

3000
Pressure (psia)

2500

2000

Case 3
1500 6600 mscf/day
Case 2 Case 4 (187 E3m3)
Case 1 2500 mscf/day 4400 mscf/day
1700 mscf/day (71 E3m3) (125 E3m3)
1000 (48 E3m3)

500 3.5" (89 mm) tubing

0
0 1000 2000 3000 4000 5000 6000 7000 8000
Rate (mscf/day)

Tubing Curve 12" (.3 m) perforation StimGun fractures 2 x 5 ft

with damage zone (.6 x 1.5 m); (1 md ft)
16" (.4 m) perforation StimGun fractures 2 x 5 ft
by-passing damage zone (.6 x 1.5 m); (infinite conductivity)

Case results
The four cases are used to generate an expected initial production rate from a reservoir and tubing with
the following properties. Reservoir pressure = 5000 psi (35 MPa); tubing pressure = WHP 500 psi
(3.5 MPa); tubing length = 8000 ft (2438 m); tubing diameter = 3.5 in. (89 mm).

Conventional:
Case 1
Ineffective Perforation (not reaching undamaged reservoir) 1700 mscf/day (48 E3m3)

Case 2
Effective Perforation 2500 mscf/day (71 E3m3)

StimGun:
Case 3
StimGun (infinite conductivity fracture) 6600 mscf/day (187 E3m3)

Case 4
StimGun (low conductivity fracture) (1 md ft) 4400 mscf/day (125 E3m3)

Conclusions when the fractures generated were assumed to have

Bypassing the damage generated by perforating little conductivity (Case 2 versus Case 4). If the frac-
using StimGun assembly can drastically increase the ture conductivity is better an even more dramatic
productivity of wells. A 76% increase in production productivity increase can be realized.
was obtained using this stimulation technique even

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Products & Applications Overview

Product testing to develop and

confirm tool performance
Joe Haney, HTH Technical Services, Inc.
Bob Daly, Marathon Oil Company

T esting of the StimGun family of products has

been ongoing for over five years. Initial test
activities were conducted mostly to validate the
characteristics of all of the StimGun family of
products.
Design objectives using high-speed pressure data
measured versus calculated burn rate properties of and computer modeling:
the various products and product variations in a
wellbore at downhole conditions. More recently, Measure and optimize burn properties
the testing program has been expanded to utilize Maximize tool performance
both downhole and surface test facilities. The sur- Allow accurate design predictions to be made
face testing program now includes basic product
Operational objectives:
testing, instrumentation evaluation, and assess-
ment of auxiliary equipment. The goal of the test- Assess product repeatability over time
ing is to further our understanding of the many Improve instrumentation, slickline-conveyance
interactive dynamic processes involved when a of the StimTube tools, design of shock
well and equipment respond to high-speed pres- absorber subs
surization.
Improve StimGun assembly components such
Test wells as rings and centralizers
Several test wells were utilized to measure, Surface tests
under downhole conditions, the propellant burn
Several small-scale high-pressure test chambers
Full-scale low pressure apparatuses
Series of full-scale unconfined block fracture
tests
Preliminary product batch testing
New product evaluation and instrumentation
evaluation

Future test activities

Assess ancillary equipment, such as packers
and plugs, under conditions of high pressure
and shock
Rate the equipment for use under dynamic
conditions
Assist the various manufacturers in creating a
dynamic rating system
Assess and document various components and
their interrelationships with other processes
Validate the calculated versus measured
relationship between tool burn rate and fluid
column compressibility
Figure 1 New product testing at Marathons Rigel #1 Study the details of propellant sleeve ignition
test well. by various perforating charges

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Time vs. pressure plots of perforation density. Run #1 and #6: 7 ft x 338 in.
Examples of field testing to determine the (2.13 m x 85.7 mm) StimGun assembly (50%
StimGun assembly propellant burn rate as a function sleeve coverage) run at identical depths.

14,000 Run #1: 2 shots per foot

(7 spm). The average burn pres-
sure is approximately 5000 psi
12,000
(35 MPa).

10,000
Pressure - psi

8000

6000

4000

2000
0.000 0.050 0.100 0.150 0.200 0.250
Time - seconds

14,000 Run #6 6 shots per foot

(20 spm). The average burn pres-
sure is approximately 8000 psi
12,000 (56 MPa).

10,000
Pressure - psi

8000

6000

4000

2000
0.000 0.050 0.100 0.150 0.200 0.250
Time - seconds

Conclusions StimGun family of products. Continued testing of

Dynamic testing of prototype products and ancillary products and equipment is critical for the long-term
components, under downhole conditions, has enabled growth and success of the technology.
the rapid development and commercialization of the

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Products & Applications Overview

Candidate well selection for the

StimGun assembly technology
Bob Haney, HTH Technical Services, Inc.

T he StimGun family of products is typically used

to fracture reservoir rock in the near-
wellbore area. In general, this fracturing process is
niques. Feasibility is a function of both the well-
bore configuration and reservoir properties.
Drilling, completion, and perforating of a well
utilized either to ensure good connection to the typically results in some near-wellbore formation
reservoir or break down the rock to enhance addi- damage. For all new wells, it is recommended that
tional stimulations. the StimGun assembly be used to improve the
perforating process. Although this damage does
Successful applications of this not always significantly impede production, the
technology include: increased cost is insignificant as compared to the
Enhanced hydraulic fracturing and acid possible returns. StimGun stimulation will not only
treatment reduce near-wellbore damage, but will enhance all
future stimulations. It can also greatly assist the
Superior tubing-conveyed completions both
reservoir engineer in completing a preliminary
underbalanced and overbalanced
productivity evaluation.
Improved gravel pack placement
For previously perforated wells where damage is
Successful near gas/oil/water contacts suspected, cost effectiveness becomes more of an
stimulation issue (especially if a work-over rig is necessary). As
Induced sand flow in heavy oil wells the total cost of the stimulation increases, the
Successful horizontal, open hole, naturally probability of success must also increase. This can
fractured, and stripper well stimulations be a difficult issue because the exact nature,
Injector well remediation degree, and extent of the damage are sometimes
unknown. The StimGun products should not used
Polymer injection enhancement for primary reservoir stimulation if there is no indi-
cation of near-wellbore damage. If there is near-
Given the wide range of potential applications wellbore damage, a propellant stimulation can be
and the three different stimulation products, it is very effective in improving production. On-site
sometimes difficult to select the best candidate interpretation of the high-speed pressure data is
well for this type of stimulation. Candidate well recommended to insure that connectivity to the
selection is typically a five-step process: reservoir has been enhanced. Multiple stimulations
Assess the application of the same zone are occasionally required to
Select the appropriate product breakthrough the damaged zone.

Complete the computer modeling

Decide if the stimulation is appropriate For all new wells, it is
Review post stimulation results recommended that the
Application assessment StimGun assembly be used
Generally all wells, at some point in their lives, to improve the
will be candidates for propellant stimulation; but
the cost effectiveness and the feasibility of the perforating process
propellant stimulation must be thoroughly
assessed. Cost effectiveness is a function of For previously perforated wells where additional
increased production/injection versus increased stimulation is required, such as hydraulic fracture
cost relative to other available stimulation tech- or acid treatment, the StimGun family of products

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can be used to improve the effectiveness of these a critical step in the process. It is quite common that
treatments. For large intervals with varying rock during the candidate selection process, the customer
properties, propellant stimulation can be used to has identified the problem (damage) and selected the
stimulate the lower permeability/porosity zones to product (1.5 in./38.1 mm OD StimTube tool), but the
ensure an even placement of the proppant or acid. modeling calculates that the stimulation will not be
In zones with high hydraulic breakdown pressure effective (fracture lengths too short due to inadequate
due to high in-situ stress and/or high rock strength, volume of propellant). The importance of computer
propellant stimulation can significantly reduce the
modeling, with accurate well information, cannot be
breakdown pressure. For damaged wells with near
over stressed. The licensed technology provider will
water/oil/gas contacts, StimGun stimulation may be
make a recommendation on the applicability of the
the only solution.
stimulation based on the results of the modeling and
Select the appropriate product the customers goals.
The three products StimGun assembly,
Post-stimulation review
StimTube tool, and Well Stimulation Tool have
very specific applications and limitations. The well- This step is critical for the evaluation of future can-
bore schematic is generally used to select the most didate wells. The validity of the candidate selection
appropriate tool. If the well requires new perforations process is verified by interpretation of the stimulation
and there are no major casing ID reductions, use the results, analysis of the high-speed pressure data, and
StimGun assembly. If there are casing ID restric- post-stimulation modeling. This post-stimulation
tions, generally it is recommended to perforate the review is also used in the stimulation optimization
well if necessary, then use the StimTube tool. If the process. As with all technologies, there is a learning
well does not need to be perforated and there are no curve. Different reservoirs are subject to different for-
casing ID restrictions, the Well Stimulation Tool is mation damage mechanisms. What works in one
recommended. There are several other considera- area might not work in another. To optimize fully the
tions, such as well temperature and fluid type, but
hydraulic fracturing of a reservoir, it may take several
these are the general guidelines. Selecting the appro-
propellant stimulations combined with tracer analysis
priate product not only increases the probability of
of the hydraulic fractures to optimize fully the treat-
success, but also can reduce costs.
ment. However, through use of our engineered
Complete the computer modeling approach of propellant-based well stimulation, many
The computer modeling ties together what the cus- near-wellbore problems with minimal risk and at rea-
tomer wants versus what the products can do. This is sonable costs can be solved.

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Products & Applications Overview

When StimGun products may be the

wrong choice
Joe Haney, HTH Technical Services, Inc.

T he StimGun assembly, the StimTube tool,

and the Well Stimulation Tool are not the solu-
tions for all problems. Based on experience, appli-
damage as a result of precipitation. This precipita-
tion of scale can take place many tens of feet from
the wellbore. Another example is a reservoir inter-
cations that are not recommended can be placed val with excessive drilling fluid loss. In some
into the following groups: instances, drilling fluid can invade the formation to
tens of feet.
Both porosity and permeability are extremely
low but all perforations are effective. Reservoir fluid sensitivity
There are no near-wellbore damage or perfora- The StimGun products will inject some wellbore
tion restrictions. fluid along with the gas generated. If the reservoir
Formation damage is very deep and extensive. is sensitive to this fluid and it cannot be easily pro-
duced back, propellant treatment can be ineffec-
The reservoir is sensitive to all available
tive or actually damaging. For example, stimulating
tamping liquids.
a low pressure gas well overbalanced with water
The wellbore configuration limits practical tool can create more damage than it removes. This
use. problem can be solved in many instances by using
Extremely low porosity and permeability a hydrocarbon tamping fluid. For all stimulations,
the selection of the tamping fluid can make the dif-
with good perforations
ference between success and failure. As has been
Effective penetration of a propellant stimulation learned for hydraulic fracturing, the base fluid has
generally extends only 2 to 20 ft (.6 to 6.1 m) to be clean and compatible with the formation.
from the wellbore, and therefore cannot replace
medium to large hydraulic fracturing or acid treat- Wellbore configuration, temperature and
ments in low porosity and low permeability reser- fluid limitations
voirs. However, in this situation, if perforation Some applications are not recommended
breakdown is difficult or has incomplete coverage, because a specific wellbore configuration is unsuit-
propellants as a pre-fracturing treatment can able. Configuration problems are usually related to
reduce horsepower requirements and control prop- diameter restrictions or proximity to packers and
pant placement. plugs. Some deep wells are too hot to maintain
integrity of propellant materials. Some wellbore
No near-wellbore damage or perforation
liquids are not compatible with certain propellant
impairment materials.
If there is little or no damage from drilling or
cementing and perforations are effective, propel- Pre-job evaluation and screening process
lant stimulation will likely not significantly increase During the pre-job evaluation and screening
the production or injection rates. process, there are certain applications that are typ-
ically not recommended. These include jobs with
Deep and extensive formation damage limited probability of success, physical restraints,
If damage extends great distances from the well- and unacceptable risks. In some instances, there is
bore throughout the entire formation thickness, no feasible solution and the technology may be
propellant stimulation may not be effective. An attempted. The following examples are generic
example is an injection well with deep formation applications not recommended.

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Examples of non-recommended applications

Example 1 StimTube tool stimulation

Production tubing: 1.9 in. (48.3 mm) minimum ID not removed

Casing: 7 in. (177.88 mm)

StimTube: 112 in. (38.1 mm) OD

This specific application would not typically be recommended because the limited tubing ID restricts the maximum possible
volume of propellant to an ineffective amount. Although there have been several successes with small tools in large casing,
the overall probability of success is low. However, in some instances, there are no alternatives.

Example 2 Some proposed StimGun assemblies in extremely long,

or in highly deviated holes
In some instances, the StimGun sleeves cannot be adequately protected from possible damage while running in hole.
Some wellbores and tool configurations could result in sleeve damage and possible single point sleeve ignition (low
pressure burn). However, most of the potential problems have been eliminated with new over-sized centralizing rings.
These rings were initially designed to secure just the sleeves to the perforating guns. This system was adequate for short
gun lengths. However, long gun strings (>20 ft/6 m) have a tendency to bow resulting in the center section of the
gun/sleeve contacting the casing. This is especially true for the smaller OD perforating guns. With the new oversized
rings securing sleeves at 3 ft (76.2 m) intervals, there should be minimal risk of sleeve damage.

Example 3 StimGun assembly stimulation

Casing: 412 in. (101.6 to 127 mm), heavy wall

StimGun: 278 in. (73 mm), 100 ft (30.5 m) of guns

The limited casing ID would prevent the use of the standard oversized rings while maintaining the recommended
clearances. Given the long gun length, use of smaller rings is not recommended. Therefore, the stimulation, as
designed, would not be advisable. Instead, it is recommended to run a smaller StimGun assembly or perforate con-
ventionally and follow with the use of a 212 in. (63.5 mm) StimTube tool.

Example 4 StimGun assembly stimulation

Horizontal well
Casing: 7 in. (177.8 mm), with 412 in. (114.3 mm) liner
StimGun: 278 in. (73 mm), 100 ft (30.5 m) of guns

Depending on the exact location of the liner top, this may or may not be a good application. Problems with entering
liners when lowering or retrieving live guns have been experienced. Every wellbore configuration must be evaluated
for potential problems. In some instances, only the WST or StimTube would be recommended.

Example 5 WST well temperature > 240F (116C); Methanal Tamping Fluid
WST: Methanol tamping fluid

The WST is not rated for temperatures greater than 240F (116C) and is incompatible with methanol.

Example 6 350F (177C)

StimTube well temperature: > 350F (177C)

StimGun well temperature: > 330F (166C)

High well temperatures and/or some fluids can reduce specific tool burn rates and tool mechanical strength. Each
applications should be evaluated for the use of a specific propellant tool.

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Products & Applications Overview

Choosing the right tool and

conveyance method
Phil Snider, Marathon Oil Company

E arly choices that the completion engineer makes

are critical. With the StimGun family of products,
there are a variety of such choices, and frequently
knowledge and assumptions about the formation
characteristics. The following flow diagram provides
a basic starting point for job design and is intended
these can have a strong effect on ultimate well per- to show the choices of whether the well will ulti-
formance. Of course, such choices are dependent mately be fracture stimulated which will have signif-
not only on products available, but also on local icant bearing job costs.

Sufficient perforations
exist?

No Yes

Yes Perforation Near-wellbore Yes

breakdown job? stimulation job?

No No

WST
StimGun assembly
Use non-damaging fluids
Inexpensive fluid systems likely Wireline conveyance possible
Wireline conveyance likely Through tubing possible
LOW COST Under/over balance not likely
LOW COST

Near-wellbore Perforation
stimulation job? breakdown job?

Yes Yes

StimGun assembly StimTube tool

Expensive fluid systems or Inexpensive fluid systems likely

Underbalanced StimGun TCP Wireline conveyance likely
Extreme overbalance StimGun TCP LOW COST
Pow*rPerf StimGun TCP
Underbalanced wireline conveyance
HIGHER COST

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StimGun sect 4a Products 9/19/02 8:40 PM Page 40

For example, if the well will be hydraulically frac- It is used on jobs with existing perforations and gen-
tured and it is not already perforated, it is usually erally conveyed on electric line. The WST is similar to
most logical to use a wireline-conveyed StimGun products that some competitors may offer. However,
assembly for combined perforation and breakdown. the added benefits of an improved ignition system,
This will provide tortuosity reduction at the lowest the Propellant Development Technology Groups
cost. If the well may produce satisfactorily without knowledge of job design, the use of PulsFrac soft-
fracture stimulation, then the engineer has to consid- ware, and the use of the IES high-speed gauge, are
er how the treatment may affect the formation. Since claims others cannot make. WST systems have been
the StimGun products will inject some wellbore fluid run in thousands of wells.
along with propellant gas, it is very important to use
StimGun TCP underbalanced jobs for low
either very non-damaging fluids (such as methanol in
pressure gas wells
a gas well) or use more exotic completion techniques
such as StimGun TCP Extreme Overbalance, StimGun StimGun assemblies can be used for underbal-
TCP Underbalance, StimGun TCP Extreme anced perforating on tubing. The propellant gives a
momentary overbalance for perf breakdown purpos-
Overbalance with the Pow*rPerf Proppant Carriers,
es, and the underbalance surge then completes the
and in some instances Underbalanced StimGun
cleanup job. The StimGun assembly for TCP appli-
assemblies conveyed on wireline. These job designs
cations in shallow gas wells can utilize a special
are certainly more expensive, but may save the cost
design feature to promote good propellant burn.
of a subsequent hydraulic fracture stimulation.
Pressure is trapped underneath the packer until the
Many case histories show that completion engi- guns fire and the propellant stimulation is finished,
neers are having success with all of the techniques. and a venting system opens below the packer to let
Frequently, what differentiates success from medioc- fluids flow up the tubing approximately one second
rity is the choice of the appropriate approach for the after the perforation and stimulation event has
given job. Some examples of tool and conveyance occurred. In this way, the tubing can be completely
selection are given below. empty to provide the maximum underbalance.
StimGun assembly on wireline Several of these jobs have been conducted in the
industry, all with very good success.
This is the most common application of the
StimGun technology, especially for perforation break- Modular TCP applications
down. A propellant sleeve is placed around a con- The StimGun sleeve has been used in even the
ventional perforating gun, also using systems to pro- more exotic TCP applications, such as the modular
tect the sleeve from damage while running in the perforating gun systems. These job designs are typi-
hole. A high-speed data gauge is attached to the cally associated with monobore completion well
bottom of the perforating gun to obtain job data designs.
and formation properties information. Several thou-
StimGun TCP extreme overbalanced jobs
sand such jobs have been run using 238 to 7 in.
(60.3 to 177.8 mm) guns. The StimGun assembly is well adapted to the con-
ventional extreme overbalance perforating tech-
StimTube tool on electric line and slickline niques, whether TCP or on wireline. In this type of
The StimTube tool was originally designed as a job, the propellant-caused breakdown of the perfora-
light-weight, through-tubing system with improved tions is followed by high-rate, gas-driven liquid injec-
mechanical strength. This tool is primarily used for tion (usually nitrogen) to extend fractures from the
remedial treatment, and over one thousand jobs wellbore and gas-saturate the near-wellbore area.
have been run. While the tool is most often run on One of the key benefits of the StimGun assembly for
conventional electric line, it will work with slickline EOB is that lower overpressure gradients are
actuators. This system is gaining favor by the opera- required, thus saving on horsepower. In many cases,
tors as a method to reduce costs of conveyance. it appears that 1.2 psi/ft (27 kPa/m) of overbalance is
adequate instead of the previously accepted level of
WST on electric line 1.4 psi/ft (32 kPa/m). Use of the IES high-speed pres-
The Well Stimulation Tool is a propellant system sure recorders and PulsFrac software is also now
enclosed in a larger carrier for mechanical protection. allowing better understanding of frictional issues, and

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Products & Applications Overview

thus better job optimization. More than one hun- permeability and/or fluid sensitivity exists so that
dred jobs have been conducted in this manner. hydraulic fracturing is impractical.
An early concern with this type of job design WST open hole horizontal well
was fear of packer failure due to the propellant applications
pulse. However, careful design has largely avoided
Despite the apparent benefits of a good near-
this problem. In fact, the failure rate with propel-
wellbore treatment over long intervals, there have
lant seems to be about the same as that observed
not been many horizontal open hole wells stimulat-
without propellant sleeves.
ed with the WST tools. All of these jobs have been
StimGun TCP extreme overbalanced jobs operationally successful, with no damaging hole
with Pow*rPerf proppant carriers collapse noted, even in some wells in marginally
This application is the same as a conventional consolidated formations. The article titled Open
StimGun EOB job, but with the addition of a carrier hole completions: case histories and technical stud-
which releases proppant to be injected with the ies with formation micro imaging (FMI) shows
surge. More than one hundred of these jobs have numerous successful case histories where the WST
been done. Many are in Canada for stand-alone has improved open hole horizontal well production.
near-wellbore stimulations, particularly where The Propellant Development Technology Group is
underlying water exists near the productive horizon. working on improved and economic propellant sys-
In fact, for some operators, it is becoming the stan- tems for these large-scale jobs.
dard completion method where sufficient formation

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StimGun sect 4a Products 9/19/02 8:40 PM Page 42

Pre-job planning
David Cuthill, Computalog Wireline Services
Bob Haney, HTH Technical Services, Inc.

A successful job requires careful pre-planning. This

should include the use of an assigned technical
specialist. Each licensee develops their own processes
Pre-job information form
Preparation of this form gets the job started. The
form is frequently filled in by the service company
and generally proceeds as follows:
and operator working together. A typical form is
1. Preparation of pre-job information form
shown below. Well schematics, history of prior opera-
2. Initial job assessment tions, logs, etc. should be reviewed in the pre-plan-
3. Preliminary computer model and job design ning process. Any potential problems should be
4. Design report mentioned.
5. Detailed job planning

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Initial job assessment Cowboy

Collapsed tubing
The initial assessment is primarily to determine: operations
can put more
Are the customers objectives reasonable? energy down
Is the job possible/practical? the hole than
is needed to
Is there adequate fluid column? do the job. To
What are the risks? (cement bond, casing be successful,
damage, wireline damage, tool loss, etc.) a propellant
stimulation
What is the best tool and conveyance must release the right amount of energy across the
method? right area over the right length of time. This will pro-
duce a peak pressure and loading rate which readily
Preliminary computer model and job
exceeds the discrete fracture strength of the formation
design rock but is less than the rock compressive strength.
If the application seems appropriate then a Also, pressure pulse inhole will not exceed the dynam-
PulsFrac computer simulation is always run. The ic strength of any of the downhole equipment.
computer model allows tool optimization for
breakdown and fracture length and quantifies 120 Good results
possible risks related to peak pressure and other WST Data require a high
100 Pinnacle Dina sands Provost area

issues such as tool jump, casing damage, packer Overlay of 12 stimulations

quality propel-
Pressure - MPa

80
loading, etc. The model may lead to design lant with
changes such as:
60 extremely
40 repeatable
Adjust liquid tamp level burn properties
20

Apply pressure from surface plus a pre-job

0
0 5 10 15 20 25 30 35 40 computer sim-
Modify tamp fluid properties Time - milliseconds
ulation on ALL
Add additional perforations potential jobs except in areas where extensive experi-
ence and/or pressure data have led to routine job
Pull tubing to accommodate a larger tool designs for specific conditions. Good results require
Increase or decrease the propellant volume high burn properties as illustrated in the 12-run over-
lay graph shown above.
Design report
If work is recommended, the report contains PulsFrac software is a very detailed, physics-based,

such items as: finite difference program which incorporates burn

PulsFrac model output data selected from more than 1000 downhole high-
speed records.
Expected results

Stimulation interval details 50 Frequent use of
Recommended perforation charges 40
the IES down-
hole gauge will
Type of guns and maximum gun lengths
lead to truly
Pressure - MPa

30

Recommended propellant tool types, sizes and

-- run #2 10.1 MPa hydrostatic 75 % coverage

20
optimized
lengths designs and
10 easily pay for
-- run #1 5.1 MPa Hydrostatic 60% coverage

Number and type of centralizers, and other

themselves,
sub assemblies 0
0.0
especially in a
0.1 0.2 0.3 0.4 0.5
Time seconds
0.6 0.7 0.8 0.9 1.0

Identification of critical steps in field operations new area. For example, after the gauge data was
recovered from run #1 (black) indicating poor per-
Recommendation to run IES high-speed
formance, more liquid was added to the well and
gauge whenever practical more propellant was used for run #2 (red) which sig-
nificantly improved tool performance and subsequent
Detailed job planning
well production.
If approved, detailed job planning and schedul-
ing commences according to the service compa-
nys and operators requirements.
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PulsFrac software: How does It

work? What does it do?
John Schatz, John F. Schatz Research & Consulting, Inc.

H igh-speed, high-energy events in a wellbore are

very complex. The ignition of a propellant tool
or perforating gun, or a combination of the two,
were predicted based on mass balance and elastic
equations, with insufficient attention paid to all of the
processes taking place in a real oil or gas well and in
begins a series of events that all occur in the time- the formation. This could lead to an overestimate of
frame of a few hundred milliseconds. Included in fracture length by as much as one order of magni-
these events are the burn of the tool, the compres- tude, and to severe mis-predictions of downhole
sion of wellbore fluids, pressure wave propagation in pressures. Wave effects and casing high-pressure
the well, casing expansion, choked flow into perfora- reflections at interfaces such as packers were often
tions, breakdown of rock around perforation tunnels, completely ignored.
the creation of new fractures around the perfs, high- The PulsFrac software, instead, incorporates all of
speed flow into these fractures causing their exten- the known processes with the use of a dynamically
sion, and high-rate leak-off into the formation. These coupled numerical solution to all of the accepted
events do not occur in sequence separately, but equations governing the interacting processes.
instead overlap in time and strongly interact. These include reaction equations for the source;
To predict job performance and ensure operational multi-phase compressible fluid flow equations for
success in a wide variety of conditions, this complex wellbore, perforation, and fracture flows; and frac-
process must be modeled mathematically with con- ture mechanics equations. No empirical curve fitting
siderable detail. This is what the PulsFrac software is used, although some approximations are used to
does. Early models, and some still in use by others, solve equations more rapidly where higher-order
were overly simplified. For example, fracture lengths accuracy is not necessary and computational speed

Figure 1 Typical output screen for PulsFrac software. Shown are graphs for mass (top), fractures (middle) and pres-
sure (bottom) vs. time, plus summaries of setup and results (right).

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Products & Applications Overview

field data. Most recently, valida-

Perf tunnel tion has been done with the use
of hundreds of high-speed pres-
sure records obtained in con-
junction with work done by
Damaged StimGun licensees. Some of
zone these are described in the article
IES high-speed/high-shock
downhole memory gauge.
An example of the PulsFrac
physical model is shown in
Figure 2. Here, choked com-
pressible flow from the wellbore
into the perforation tunnels cre-
ates time-dependent pressuriza-
Failure tion. Subsequently, a damaged
initiation cylindrical zone around the perf
expands and eventually, if pres-
sure is high enough, fails in ten-
Figure 2 An example of the physical model for perforation breakdown and
fracture initiation.
sion. Then further choked flow
proceeds into growing fractures.
is important. All solutions are done with a time- To set up and run the PulsFrac software, the
marching finite difference technique optimized to user inputs all of the known information about
run on a standard personal computer. Output is the formation, well, and tool. Then an initial run
graphical and easily interpreted for use in job is made. In subsequent runs, adjustments are
design. An example is shown in Figure 1. Many made to tool sizes and other controllable param-
other screens and reporting formats are available. eters, such as perforation schedule and fluid
This software is unique but is based on aca- tamp, to optimize the job and minimize risk. If
demic and commercial work done in the defense data are obtained with the high-speed downhole
and energy industries over the past 30 years. The recorder, calculated and measured results are
accuracy of results is validated by an ongoing compared after the job to determine job success
series of comparisons with exact theoretical mod- and aid in future planning.
els of simple events, laboratory experiments, and

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IES high-speed/high-shock downhole

memory gauge
Scott Ager, Instrumentation and Engineering Services, Inc. (IES)

T he oil and gas industry has used downhole pres-

sure gauges for a number of years. The most
accurate of these use quartz transducers and are
A total of one million data points can be recorded at
12-bit resolution (approximately 0.02% of the user-
set full scale). Standard industry gauges are complete-
designed to collect precise data over long periods of ly incapable of this level of performance.
time (many minutes to hours, days, and even
months). Some of these gauges record and store
data downhole as memory gauges, and others
transmit data up the hole on wireline for remote
storage. Sampling rates are seldom faster than one
point per second. Until now, this gauge style has
been sufficient for monitoring the quasi-static or
slowly-changing pressures associated with well test-
ing and production.
New pressure gauge for the oilfield, an
added benefit to StimGun technology
development
The ability to routinely measure dynamic pres- Figure 1 Projectile with IES gauge shot though a 1 ft (.3 m)
sures and associated accelerations is key to the inte- concrete target.
grated engineering approach used for the design,
analysis, and performance of the StimGun family of
products. IES has developed a new oilfield pressure
gauge based on unclassified military technology that
not only will withstand the high accelerations associ-
ated with propellant events, but will also record and
store data at extremely high rate.
Pressures up to 30,000 psi (207 MPa) and events
that occur in a few tens of milliseconds (1 ms =
1/1000 of a second) must be measured and
recorded. This requires a time resolution of about (a)
ten microseconds (1 s = 1/1,000,000 of a second)
or better, corresponding to 100,000 data points
per second.
The current IES oilfield gauge records data in a
frequency range of 0 Hz (1 Hz = 1 per second) to
10,000 Hz, with an actual sampling rate of
115,000 Hz. The pressure transducer is rated to
30,000 psi (21 MPa). Various housings are available
that are rated in excess of 20,000 psi (138 MPa).
The current temperature rating without thermal
protection is 253F (123C). Special thermal hous-
ings can increase this rating. The gauge can also be (b)
used to measure tool movement, acceleration, and
Figure 2 (a) 2000 lb (900 kg) projectile with IES gauge. (b)
vibration levels up to 50,000 Gs ( 15,240 m/s2). Shot though a 10 ft (3.1 m) concrete target.

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Products & Applications Overview

Figure 3
Buffer Stack Test
The Air Force wanted to see how effective a concrete
buffer would be in preventing one stack of 500 lb
(227 kg) bombs (256 bombs total) from detonating
when another stack of 256 bombs (128,000 lbs
(58,000 kg) of TNT) exploded on top of them. The
purpose of these tests was to design a buffer that
would prevent additional explosions if the enemy
succeeded in hitting one stack of bombs.
To learn how effective different types of buffers were,
the AF needed to collect the pressure data generated
by these massive explosions. The problem was that
pressure sensors and the wires were almost instantly
being destroyed. The AF came to IES to build a
gauge to withstand these huge explosions and collect
the pressure data for later retrieval. IES used 12 of
its recorders to monitor the pressure generated by
this blast. They were placed inside the second stack
of inert bombs, as shown in the picture.

The Explosion
128,000 lbs (58,000 kg) of TNT was ignited on one
side of the buffer and on the other side were the
12 IES recorders. The explosion was large enough
that it was heard 75 miles (121 km) away.

The Crater
The blast was so powerful that it made a 15 ft
(4.6 m) deep crater, large enough to put a three-bed-
room home in. Some of the inert bombs with the IES
recorders where hurled over a mile away!
The test was a success, and IES recorders collected
pressure data from the blast for the first time.
600

Expected pressure
500
Pressure at
charging well
400

Test Data
Pressure - psi

300
This graph shows the data acquired from the tests,
200
in psi versus time in milliseconds. The red line is the
military engineers computer prediction of the pres- 100
sure trace, while the blue line is the actual data
acquired from the IES recorder. As can be seen, the 0
actual data validates the engineering predictions.
-100
0.5 1 1.5 2 2.5 3
Time - milliseconds

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burn and determine the breakdown fractur-

ing response of the formation with the
PulsFrac software. Please see the article,
PulsFrac Software and high-speed
Recorders used to Design & Confirm
Propellant Behavior and Formation
Fracturing.
Other applications of the IES gauge
Other applications include recording tool
movement, perforating gun performance,
hydraulic fracturing response, and reservoir
Figure 4 The IES Series 200 High-speed Pressure/Acceleration Gauge. transient measurements. The gauge can
The series 200 gauge is typically mounted below the StimGun assem- record four channels of data and is fully user-
bly, StimTube tool or WST carrier. configurable. For example, the output from a
pressure sensor, an RTD temperature sensor, a
Instrumentation and Engineering high-G accelerometer ( 50,000 G / 15,240 m/s2)
Services, Inc. (IES) and a low-G accelerometer (10 G/3 m/s2) can be
IES has been in the business of building custom, recorded. Figure 6 shows pressure and tool move-
miniature, high-shock data recorders for military and ment obtained from the double integration of low-G
commercial applications since 1987. accelerometer data. Figure 7 shows how multi-speed
IES recorders have been used to collect acceleration data can be used to record tool run in and out, high-
and deceleration data for projectiles (Figure 1), and speed pressure, and temperature. Figure 8 shows the
stress/strain measurements of projectiles leaving use of the IES gauge for recording transient response
7 in. (177.8 mm) naval guns, and impacting rein- of the formation.
forced concrete targets up to 15 ft (4.6 m) or more The IES high-speed gauge is extremely versatile.
(Figure 2), and not only survive, but record the data Other than its main current use of verifying tool per-
collected in these severe environments. formance, only a fraction of its potential uses have
IES recorders have also been used to collect pres- been fully exercised. The Propellant Technology
sure data in other extreme environments, such as Development Group is constantly looking at new
beneath the detonation of 128,000 lbs (58,000 kg) gauge applications and finding ways of assisting
of high explosive (Figure 3), and inside electromag- licensees and their customers to better utilize this
netic railguns. unique technology.

These advances in gauge tech-

nology have been brought to the
oil and gas industry, as the IES
Series 200 High-Speed Pressure
Gauge (Figure 4).
Gauge data verifies tool burn
and in conjunction with
PulsFrac software deter-
mines fracture responses
The pressure profile collected is
shown in Figure 5. This profile is
used to verify the propellant tool

Figure 5 Typical gauge data show-

ing pressure, temperature, high-G, and
low-G acceleration data.

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Products & Applications Overview

Figure 6 Tool movement vs. 27

time (and pressure) calculated 24
by integrating the low-G 21
accelerometer data collected by 18 Pressure mPa
the gauge. Tool movement meters
15

Meters / mPa
12
9
6
3
0
-3
-6
*
-9
-1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00

Time - seconds

10 45
Figure 7 The multi-speed
sampling rate mode of gauge 9 40
operation gives the operator the Ignition
8
ability to collect pressure data 35
at a slow sampling rate before 7
and after the high-pressure 30
Pressure - mPa

6 Temperature

Temp - C
event and continue to sample
25
high-speed pressure data 5
(115,000 data points per sec- CCL 20
ond) when the tool is burning. 4 correlation
3 15

2 10
Pressure
1 5

0 0
5 10 15 20 25 30 35 40 45 50 55 60 65
Time-minutes

Figure 8 Slow-speed data

from two IES high-speed 3000
OWR
recorders (OWR) compared
with another gauge capable of OWR shut
slow speed only (HMR). The 2500 HMR in
IES gauges were run at the perf
gun and the HMR gauge was
Pressure - psi

2000
located 100+ ft (30.5 m) above
the gun.
1500 open to
flow

1000

500

0
2550 2700 2850 3000 3150 3300 3450 3600 3750 3900
Time

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PulsFrac software and IES

high-speed memory gauges used to
design and confirm propellant
behavior, perforation breakdown, and
formation fracturing
John Schatz, John F. Schatz Research & Consulting, Inc.
Bob Haney, HTH Technical Services, Inc., Inc.
Scott Ager, Instrumentation and Engineering Services, Inc.

P ropellants, by themselves and now combined with

perforating guns such as the StimGun assembly,
have the potential to break down and clean up dam-
wellbore/formation response occurs in the same time
frame or only slightly longer. Dynamic events cause
motion. Both propellants and perforators create
aged perfs, penetrate near-wellbore damage, and cre- dynamic events. The burn of a propellant in oil field
ate fresh formation fracturing. In the past, the use of application generally has a duration of 10 to 100 ms,
propellant tools has been limited by a lack of standard while standard perforating guns fully ignite in
design, measurement, and analysis techniques. 1 to 10 ms (for the whole gun), while each high explo-
Presently, ultra high-speed downhole memory gauges sive event occurs in the microsecond time range.
and computer software that incorporate well, perfora- In the past, dynamic treatments and tools were
tion, and tool details solve this problem. The use of designed mainly on experience, and results were ana-
software and gauges by the Propellant Technology lyzed only on post-job well performance. Although
Development Group and its licensees are described, post-job well performance is clearly the most important
issue, a better understanding of dynam-
ic tool behavior, well response, and for-
mation response contributes immensely
a better understanding of physical to future tool improvements, the avoid-
behavior leads to better treatments ance of mistakes, and making an opti-
mal selection among a choice of tools.
and better long-term returns As with other well-developed technolo-
gies such as hydraulic fracturing, a bet-
ter understanding of physical behavior
and several examples are presented that show the use leads to better treatments and better long-term
of this technology in the field. High-speed pressure returns. Also, an ability to accurately predict and record
data are compared with calculations to show the real- these downhole events is the ultimate quality control
ism of results. The combination of the gauge and soft- tool. In the past, the lack of this capability has
ware for design and evaluation of dynamic well treat- undoubtedly contributed to a relative under-utilization
ments allows the optimization of job design, and the of propellant treatment techniques.
evaluation of post-job results. This data allows the
To achieve full high-speed data acquisition capabili-
group to understand tool performance and improve
ty at 100 kHz or greater and the corresponding com-
future tools and applications.
putational capability, it has been necessary to devise
Propellant and perforating tools are in a class of new techniques of measurement and calculation. The
devices that create high-speed, or dynamic (rather first efforts along these lines, outgrowths of govern-
than static or quasi-static) pressurization. The word ment-sponsored technology, showed good promise
dynamic is used here to mean that the source tool but were not immediately well-suited to actual oilfield
releases all of its stored chemical energy in less than a operations. The objective of our more recent work is
few hundred milliseconds (ms), and that the to advance high-speed downhole data acquisition

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Products & Applications Overview

5000 to 20,000 psi (35 to 138 MPa)

range at about 1 to 10 ms, followed by a
Wellbore
interior decay tail associated with expansion, cool-
Tamping
liquid ing, and flow into perforations and frac-
tures. The exact character of this burn,
Fluid motion
Expanding in well
expansion, and flow-related pressure curve
gasified is highly dependent not only on the tool
bubble
itself, but also on the well diameter, confin-
Propellant ing fluid compressibility and depth, perfo-
energy Flow through ration area, and formation properties.
source perforations and These types of propellant tools are also
into fracture
used in open hole applications.
(Two fractures
shown)
Perforating guns. Clearly, the main pur-
High-speed
recorder pose of a perforating gun is to create holes
in the casing and subsequently penetrate
the formation. Individual explosive charges
ignite and detonate in the microsecond
time range and create localized pressures in
excess of 100,000 psi (690 MPa). Whole
guns ignite in a time period on the order
0.1 ms per foot of length. However, not all
Figure 1 Generic well configuration as the propellant energy is of the charge energy is expended in doing
released. the work of making holes and channels.
and matching numerical computation techniques Some is left as energetic residual gases that
to allow full design and analysis of wellbore expand and act much like the products of a pro-
dynamic events in a mode suited to petroleum pellant burn over a several milliseconds time peri-
industry operations. To a great extent this effort od. The amount of such residual gas varies with
has been made possible by concurrent industry the gun type and other conditions and has not
been thoroughly tested or documented, but prob-
advances in electronic data acquisition and com-
ably is in the range of 25% to 75% of the charge
puter system hardware and software.
energy. This is identified as remnant energy.
Brief review of tools and methods used Combined perforating guns and propellants,
for dynamic well treatments the StimGun assembly. Recently, propellants
Various tool designs in past or present use are have been combined with perforating guns in the
describable as dynamic. A generic well configura- StimGun assembly. The propellant is placed as a
tion is shown in Figure 1. Although many dynamic cylindrical sleeve around certain perforating guns,
tool types exist, most can be categorized as follows: forming an assembly where the perforating charge
ignites the propellant. The intention of this device
Propellants. Many early and some current pro-
is to perforate, break down, clean up, and mildly
pellant tools are cylindrical canisters of granular
stimulate in one step. The perforation event causes
gunpowder-like propellant. Instead, the WST and
a relatively large, early pressure spike of short
StimTube tool consists of resin-molded cylindri- duration followed by a propellant-like event. The
cal propellant, which is much more amenable to remnant energy from the perforating charge cre-
routine oilfield use. These tools are usually less ates a pre-pressurization that changes the subse-
than 20 ft (6.1 m) long, but lengths of up to quent propellant burn rate and may improve frac-
1000 ft (305 m) have been used. Burn durations ture penetration.
vary from tool to tool, but most fit into the
Other dynamic tools and techniques. True
100 ms burn time mentioned above. Burn prod-
explosives (other than in perforators) have been
ucts are mainly energized and expanding gases in use in the oil industry for years, but discussion
such as carbon dioxide and water vapor. These is excluded here because of their relative lack of
tend to create a pressure pulse with a peak in the

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current use and highly uncertain results that are dif- become possible. This means that tool selection can
ficult to control. Extreme overbalance perforating be optimized, user-controlled variables set (such as
and/or stimulation, with or without a fast-acting valve well fluid type and depth), and problems avoided
or rupture disk, is in current use and has been meas- (such as undesired packer loads). This process is in
ured and analyzed with the techniques described many ways similar to that for hydraulic fracture
here. Discussion is excluded for now because of the design. Simulation calculations are made. These are
small amount of high-speed data available. compared with previous high-speed downhole pres-
Typical well and formation response all tools. sure data. Changes are made to be appropriate to
All dynamic-burn tools create a highly time-varying the new well to be treated. The design is optimized.
pressure pulse dependent on many tool, wellbore, Finally, new high-speed downhole data are
perforation, and formation parameters. Several differ- obtained and the information added to the data
ent ignition systems are presently in use and are a bank for future use. Additional dynamic measure-
crucial factor in the character of the subsequent burn. ments are possible and potentially useful. These
Following ignition, and both during and after the include acceleration, which is a measure of tool
burn, the expanding residual gases can break down motion and can be compared with calculation. The
perforations that are damaged. Newly created forma- IES high-speed downhole memory gauge and
tion fractures emanate from perforations (or from the PulsFrac software have been designed to achieve
wellbore wall in a non-cased well). These fractures these purposes. Both are further described in other
tend to be radial, but can have highly complex articles in this publication.
detailed shapes. Multiple fractures (generally six or
less) can form, but a large
number of multiples cannot
propagate for great distances The first dynamic wellbore pressure
due to ultimate stress and flow measurement technique was a
restrictions. Compared to
hydraulic fractures, fracture
mechanical peak pressure device.
lengths are not large, usually
less than 20 ft (6 m), but firm evidence exists for Field data and analysis examples
improved breakdown, clean up, and mild stimulation.
In the well, the expanding gasified zone creates wave Three examples are described where computer cal-
motion that propagates both upward and downward. culations are used to interpret high-speed data. Most
These pressure waves, which have been observed in of the application types are covered by these exam-
gauge data, can strike packers, plugs, tubing and/or ples, although the possible variations in actual field
casing diameter changes, and other full or partial use are innumerable. The examples include a simple
obstructions and create large local dynamic loads. cylindrical propellant in an open hole, a perforating
The fluid motion associated with the waves can also gun, and a StimGun assembly in a cased hole.
accelerate and move wireline-based equipment, caus- Propellant in open hole. The first example shows
ing problems if motion is excessive. This general the basic ability to measure and calculate dynamic
inhole pressurization and motion, and the potential events. It is for a cylindrical 2 in. (50.8 mm) diameter
for overpressurization local to the tool, strongly sug- by 10 ft (3.1 m) long WST propellant device. The
gest that careful measurement, design, and experi- wellbore is 6.25 in. (159 mm) in diameter and the
ence are very important for the repeated success of working depth is at 1295 ft (395 m) in a 120 md gas-
this type of work. bearing formation. For this job, it was desired to
maintain the lowest hydrostatic pressure possible to
IES high-speed memory gauge and avoid undue initial liquid injection to the formation.
PulsFrac software The well was filled with KCl water to 695 ft (212 m)
With an accurate and reliable downhole dynamic from the surface and overpressured at the surface
pressure measurement device, a consistent and with 400 psi (2.8 MPa) of nitrogen to encourage a
well-defined energy source, and software that can good burn pressure but still keep hydrostatic pressure
model a wide variety of tool, wellbore, and forma- low. This special procedure was developed with the
tion behaviors, true treatment and tool design help of the calculations. Figure 2 shows the calculated

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Products & Applications Overview

Figure 2 Calculated and measured pressures, and calculated fracture length for open hole propellant example.

Figure 3 Calculated and measured pressures for perforating gun example.

pressure and fracture length along with high-speed hydrostatic pressure and yet enough burn pressure
gauge pressure data to a time of 50 ms. to grow fractures can be achieved by use of the
As indicated by the vertical dashed line, the pro- design software and validated by collecting high-
pellant burn ends at about 38 ms. The measured speed data.
peak pressure is about 16,000 psi (110 MPa) at Perforating Gun. The second example shows
about 3 ms. Calculated and measured pressures the measured and calculated dynamic pressure
nearly overlay. This is a frequent occurrence for behavior for a perforating event. It is for a tub-
relatively simple configurations such as this. ing-conveyed 3.5 in. (89 mm) 6 shots per foot
Standard burn parameters were used and not (spf) (20 spm) perforating gun in 5 in. (127 mm)
adjusted to match data. Four fractures (two bi- casing in a deviated hole. The job is somewhat
wings) are calculated. A length of 4.8 ft (1.5 m) unusual in that the gun assembly is 910 ft
(each wing) is achieved by 50 ms on the longest (277 m) long. The working zone is in a low-per-
stress-preferred wings. The shorter wings (not meability formation at approximately 7500 ft
shown) reach 3.4 ft (1.03 m). A small amount of (2286 m) true vertical depth. Figure 3 shows
additional growth (not shown) may continue to measured pressure and several calculated pres-
occur after 50 ms. sures to 80 ms. The time scale of the figure begins
This example shows that non-complicated con- at the actual ignition time of the gun. The high-
figurations are routinely measured and calculated. speed memory gauge is placed at the bottom of
Design objectives to maintain low, long-term the gun and thus does not see a signal until the

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Figure 4 Calculated and measured pressures and fracture StimGun example.

ignition arrives at that location after about 40 ms. StimGun assembly. The third example is a propel-
Then there is a spike in the measured pressure to lant sleeve-perforating gun assembly. The well is a rela-
about 13,000 psi (90 MPa), marking the arrival of tively high-permeability (100 md) water injector with
the ignition pulse at the gauge, followed by a slowly- the working horizon at approximately 4300 ft
decaying pressure to 5000 psi (35 MPa) at 80 ms. (1311 m). The job is a recompletion in 5.5 in.
Three calculated pressures are shown, one at the (139.7 mm) casing with a 15 ft by 338 in. (4.6 mm by
gauge location to match the data, one immediately 85.77 mm) gun at 6 spf (20 spm). A 4 in. (101.6 mm)
above the tool, and an average of the pressure within propellant sleeve was used. Figure 4 shows measured
the ignited part of the gun. The calculated pressure at and calculated pressures and calculated fracture length
the gauge is a reasonably good match except for the to a time of 100 ms. Peak pressure is about 11,000 psi
actual spike tip, which is somewhat high. This tip is (76 MPa). Measured and calculated pressures agree.
very sensitive to gun volume and gun efficiency and is All of the perfs are broken down (not shown) and frac-
tures extend from the stress preferred to 1.5 ft
expected to be difficult to match. The calculated pres-
(.46 m). Non-stress preferred fractures extend to
sure immediately above the gun is very different from
about 1.3 ft (.4 m). Fractures are relatively short
that below. The pressure below the gun is enhanced
because of the high-permeability of the formation,
because the ignition is moving downward while the
which causes a leak-off-related fracture length limita-
pressure above is diminished because the ignition is
tion, even at this short time scale. In actuality, early
moving away. Shorter guns do not display this ten-
leak-off might be restricted by near-wellbore damage,
dency, and the pressure waves moving upward and
which would increase fracture length. This can be
downward are more symmetric. The calculated curve
modeled but is not shown here. Maximum calculated
for the average pressure in the ignited part of the gun
fracture width is about 0.02 in. (0.51 m) and fractures
smoothly moves up to a peak of about 7000 psi
remain open until 95 ms.
(48 MPa), which occurs at the end of ignition.
This example shows that perforating gun response Conclusions
even without the presence of propellants can be Dynamic well treatment techniques, usually incor-
measured and calculated. There is some sensitivity to porating propellants, create wellbore conditions that
gun parameters that are not ordinarily known, but are difficult to understand and control without mod-
with increased recording of data for many different ern measurement and design techniques. During the
guns, that deficiency will eventually be overcome. past several years, and with the help of advances in

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Products & Applications Overview

digital hardware and software technologies, it When important tool, well, and formation
has become possible to measure high-speed parameters are known or well-estimated,
downhole pressure and acceleration events, the software has true data-matching and
and simulate them in software with an accuracy predictive capability and can be used for
that makes true design and job analysis possi- reliable design.
ble. This work, and the demonstrative examples Calculated fracture lengths for most dynamic
shown here, lead to the following conclusions: treatments are usually modest, under 20 ft
The IES high-speed memory gauge and (6.1 m). It is implied that these treatments
PulsFrac software work well in combination are successful due to perforation breakdown,
to assist in the design and understanding of cleanup, and near-wellbore fracturing. That
a wide variety of dynamic treatment types. is, the perforations occur as intended.

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Big-Block surface test of the StimGun

assembly
Brent Kirschner, Owen Oil Tools
John Schatz, John F. Schatz Research & Consulting, Inc.

A n instrumented, big-block surface test was con-

ducted to study the perforation (perf) breakdown
effects of StimGun assembly. The test used an 8 ft
the 8 ft (2.4 m) diameter, 40,000 lb (18,143 kg)
API- style target is opened and rolled backwards
on its sides (Figures 1 and 4).
(2.4 m) diameter, 40,000 lb (18,143 kg) API-style Post-shot examination of the target showed
target. The target was poured around a 5 in. fractures in the plane of the perforations. This is
(130 mm) casing. A 218 in. (54 mm), 6 spf (20 spm)
highly significant and confirms the suggested
StimGun assembly was placed in the target. A high-
mechanism of tool action.
speed gauge recorded internal pressures. Fifty represen-
tatives of major service and production companies Significant erosion of the perforation tunnels by
observed the test, and a video record is available for the high-pressure gas generated from the
viewing. Several important observations were made StimGun assembly was seen. This suggests that
from of this test: the crushed zone of the perforating tunnel can
The StimGun assembly has sufficient energy be reduced in thickness or removed, resulting in
content available to do the work of perforation improved permeability and increased production
breakdown and fracture extension. A qualitative The PulsFrac computer code was validated by a
demonstration of the energy content was seen as good match with the pressure record.

Test description
This test consisted of a molded StimGun assembly with 2.03 in. (51.6 mm) carrier diameter and 2.68 in.
(68.1 mm) propellant diameter placed in a cased, poured concrete cylindrical target 8 ft (2.4 m) in diameter.
The gun was approximately 4 ft (1.2 m) long and was initiated with 6.4 g charges at 60 phasing and 6 spf
(20 spm). Casing was 5.12 in. (130 mm) outside diameter and 4.25 in. (108 mm) inside diameter. The hole
was water-filled. Two OWR-connected fast pressure gauge probes were placed near to the top. Figures 1 and
2 show the StimGun assembly and target assemblies.

Figure 1 96 in. (2.44 m) API target being shot with a 218 in. (1.2mm) Figure 2 218 in. (54 mm) diameter,
StimGun assembly. 4 ft (1.2 m) long StimGun assembly
used in the test.

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Products & Applications Overview

Field results
The test fully fractured the block into
four large irregular pieces and several
smaller pieces. It was expected that
three large pieces would be formed,
but one of the large pieces apparently
split, resulting in four. The overall post-
test appearance is shown in Figure 4.
Upon examination, approximately
50% of the perforation tunnels
showed clear evidence of being frac-
tured by injection during the propel-
lant burn phase. The evidence consist-
ed of stains on the fracture faces and
an irregular surface suggesting erosion
and fracture extension, rather than Figure 3 Test assembly of the 96 in. (2.44 m) API target.
simple tensile extension caused by
boundary relief. Some of these frac-
tures emanating from the perforation
tunnels are shown in Figure 5. Good
high-speed pressure data were Protective cap
obtained from one of the probes and
are used for the following PulsFrac-
based analysis.

Computational results
The data and PulsFrac run results are
shown in Figure 6. The lower graph
shows the fast gauge data. Several ini-
tial spikes in the 0-10 milliseconds (ms) Wellbore casing
time range, related to perf gun ignition,
are followed by a broad peak of about
25,000 psi (172 MPa) beginning at
22 ms and extending to 35 ms. Finally, Figure 4 Post-test fractured target
there is a pressure decay to 100 ms and
beyond. (The raw data continues to
about 500 ms.)
The third graph in Figure 6 shows
the computed simulation. The early
spikes are now seen to be associated
with internal reflections in the 4 ft Perf tunnel
(1.2 m) casing section. Then, a delay Perf tunnel Perf tunnel
of about 8 ms in propellant lightup is showing fracture
probably related to the propagation emanating near
entrance.
of the burn front over the surface of
the propellant. If the propellant sleeve
was slipped on, rather than molded,
this delay might have been shortened
due to fracturing of the sleeve. In this
case, it appears that the sleeve did not Figure 5 Perforations and fracture surfaces.

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PulsFrac
Prediction

Gauge Data

Figure 6 Pressure data and PulsFrac results from the big-block surface test.

fracture significantly since a characteristic length of The first graph of Figure 6 shows the mass rates.
the propellant fragments is 1.6 in. (40.6 mm) or more Of most interest here is that the fluid injected into
was required to model the burn. Although the flattened the fractures consists of about 40% gas and 60%
peak pressure in the raw data appears to be related to water. This was not directly measured in the field,
clipping, it is interesting to observe the flattened peak in but the high-speed camera record shows a cloudy
the computer simulation. This occurs as the external substance emanating from the fractures, which
pressurized medium is bleeding into the interior of the would be consistent with a mixture of propellant-
expended gun and there is a temporary balance related gases and atomized water.
between burn and bleed rates. Finally, at about 35 ms,
the burn ends and decay occurs due mainly to fluid Conclusions
escaping into the fractures. The bleed-down rate in the PulsFrac calculations and field data are in agree-
raw data is greater than in the calculated because the ment. Propellant light-up delay and relatively slow
fractures reach the surface of the target in the real test, burn are consistent with the molded-on propellant
while PulsFrac assumes the walls are located far away. not fracturing significantly as a result of the gun
The second graph of Figure 6 shows fracture width burn. Fractures break the target surface by 30 ms
and length. Three fractures were used in this model after that; decay in the field pressure data is faster
to approximately simulate the field event. Fracture than the calculation due to venting to the atmos-
length exceeds 25 ft (7.6 mm) and is still growing. phere. Perhaps the most significant result is that
This is of course unrealistic since the target bound- about 50% of the perf tunnels fracture along a signif-
aries would have long since been reached. More icant proportion of their length and that PulsFrac
important is that the outer boundary of the target is modeling is consistent with this type of fracturing.
reached by the fractures by 30 ms. After that, the This is a clear demonstration that the presence of the
pressure decay would be accelerated due to the frac- propellant in the StimGun assembly creates true
tures opening to the atmosphere. Comparing the perforation breakdown and frac extension, thus
computation to the data supports this. enhancing connection to the formation.

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Products & Applications Overview

Using the IES high-speed gauge

in TCP drop bar applications
Casey Weldon, Baker Atlas
Alphie Wright, Baker Atlas

T he IES Series 200 Gauge can be configured as

a drop bar (Figure 1) as commonly used in
many TCP jobs. In this configuration, it can pro-
points per second, and one million total data
points are available, which enable a wide range of
possible combinations, depending on the users
vide valuable information such as liquid level, bar needs. Some selected data plots from test runs,
velocity, confirmation of tool ignition (either perf along with detailed explanation are presented in
gun or propellant), immediate formation pressure this article.
response, and longer-term pressure buildup.
Multiple sensors, multiple time windows, multiple
Test run results
sample rate combinations up to 115,000 data Figure 2 shows acceleration data from three simi-
lar runs where the instrumented bar was dropped
through 1000 ft (305 m) of air and 500 ft (152 m)
of water in 278 in. (73 mm) tubing. In this overlay,
278 in. (73 mm) tubing the release of the gauge, free-fall though air,
(2.441 in./62 mm ID) impact with the fluid, travel through the fluid,
passing through a restriction, and final impact with
the firing head, are all clearly indicated.
Looking at these data in more detail, many fea-
Fluid level @ 1000 ft (305 m)
tures of behavior are seen. The initial release accel-
erates the gauge to +1 G (32.3 ft/s2), and the
velocity of the gauge (Figure 3) can be calculated
278 in. (73 mm) tubing by integrating the accelerometer data. Integrating
(2.441 in./62 mm ID) again gives the distance traveled (Figure 4). As the
velocity increases, the acceleration starts to fall. If
terminal velocity were reached, acceleration would
278 in. (73 mm) Sliding sleeve @1488 ft (454 m)
(2.313 in./58.9 mm ID)
be zero, but the gauge reaches the liquid first. The
small spikes in the acceleration data are the gauge
striking the casing during its descent.
278 in. (73 mm) tubing
(2.441 in./62 mm ID) The large negative spike in the accelerometer
data is generated by the liquid contact. At that
point, the gauge comes almost to a stop, and the
liquid column is greatly disturbed. Then, as the
gauge starts to travel through the liquid, its accel-
eration and velocity oscillate in relation to the liq-
Mechanical firing head @ 1500 ft (457 m) uid column moving up and down. This oscillation
diminishes with time and as terminal velocity is
approached in the liquid.
The gauge travels through 500 ft (152 m) of liq-
338 in. (85.7 mm) Peforating gun loaded with uid water in 278 in. (73 mm) tubing until it
detonating cord only
encounters a 238 in. (60.3 mm) restriction in the
tubing. This causes a deceleration and loss of
End of overall assembly @ 1522 ft (464 m) gauge velocity, which can clearly be seen. When
the gauge finally impacts the inert firing head,
Figure 1 Drop bar testing well configuration. there is a large negative acceleration as the gauge

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30 Figure 2 Overlay of low-G accelerometer data

from the 3 test runs. The bar was dropped through
15 1000 ft (305 m) of air and 500 ft (152 m) of water
0 in 278 in. (73 mm) EUE tubing.
l
Release bar
Bar restricted
Acceleration - ft/s/s

-15
in tubing
-30
Bar contacts
-45 fluid -- Bar impact
Runs 1, 2 & 3
1000 ft air, 500 ft water firing head
-60
acceleration ft/s/s
-75

-90

0 5 10 15 20 25 30 35 40 45
Time - seconds

240 160
Bar contacts Figure 3 The velocity integration of the
fluid
210 accelerometer data indicates a maximum speed of
Runs 1 2 & 3 - 1000 ft air 140

180
velocity integration 215 ft/sec (65.5 m/s), 150 mph (241 km/hr) and
120
still accelerating before contact with the water.

Velocity - mph
150
100
Velocity - ft/s/s

120
80
90
run 1 60
60 run 2
run 3 40
30
Release 20
bar
0
0
-1 0 1 2 3 4 5 6 7 8
Time - seconds

1000
Bar impacts fluid -- Figure 4 The distance integration calculated
900 from the accelerometer data during free-fall indi-
800 cates the water level should be 960 to 980 ft
700 Runs 1,2 & 3 - 1000 ft air (293 to 299 m), later confirmed by direct measure-
distance integration ment at 975 ft (297 m).
600
Distance - ft

500

400

300 run 1
run 2
run 3
200

100
Release bar
0
0 1 2 3 4 5 6 7 8

Time - seconds

500 Figure 5 Drop bar gauge pressure data overlay

Runs 1 2 & 3 500 ft water of the first four drops (time normalized to water
450 Bar
contacts run 4 1000 ft air Bar
400 fluid -- impacts contact). Travel time for 1000 ft (305 m) of air
firing and 500 ft (152 m) of water = 37 seconds. Travel
350 head
(Run 4) time for 500 ft (152 m) of air and 1000 ft (305 m)
300
of water = 64 seconds. A pressure decrease was
Pressure - psi

run 1
250
run 2
observed as the pressure sensor passed each cou-
200 run 3 pling.
run 4
150

100 Bar impacts

firing head --
50 (Runs 1, 2 & 3)

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
Time - seconds

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Products & Applications Overview

comes to rest. The oscillations that occur with column bouncing up and down as the gauge
impact are the result of multiple impacts as the enters the fluid. The average pressure rises as the
gauge bounces on the firing pin. gauge travels deeper, and the oscillations are
The pressure data (Figure 5) also clearly shows damped. The impact with the inert firing head can
the water impact, travel through the liquid column, be clearly seen. If there had been an actual gun, the
and impact with the firing head. When the gauge gauge would have been triggered into the fast sam-
first hits the water, the pressure jumps from the pling speed mode upon firing. The gauge could
sudden rush of liquid against the pressure sensor. then be left downhole to collect inflow pressure
The pressure oscillations are created from the water data, then later retrieved. Also if the gun had mis-
fired, the gauge data would clearly indicate this.

[the drop bar]

configuration can provide
valuable information such
as liquid level, bar
velocity, confirmation of
tool ignition (either perf
gun or propellant),
immediate formation
pressure response, and
longer-term pressure
buildup
The IES Series 200 gauge being used as a drop bar.

The IES Series 200, 11116 in. (42.9 mm) gauge with drop bar subs. This gauge is outfitted with pressure, temperature,
shock (high-G), and acceleration (low-G) sensors.

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A massive hydraulic
fracture stimulation
operation. It would be
nice to know that all
the perforations were
open.
StimGun sect 4b 9/19/02 8:53 PM Page 63

A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

An interview with Buddy Woodroof,

ProTechnics technical manager
Paul Gardner, Marathon Oil Company

Gardner: Buddy, thank you for sitting down

with me to give me your perspective
on the StimGun technology. But first,
can you tell me a little about your
background both before and after
joining ProTechnics?
Woodroof: I spent my first fifteen years in
Chemical Research & Development
with the Western Company, rising to
the level of Manager of Chemical R&D.
I then became a region technical man-
ager for Western and subsequently BJ
Services. I have spent the last five years
as Technical Manager for ProTechnics. Buddy Woodroof and Paul Gardner.
In these capacities, I have had the ben-
efit of several perspectives on comple- Woodroof: A statistical analysis of our extensive
tions, namely, developing the fluids and spectral GR image database has deter-
additives, designing the treatments mined that approximately 40% of the
employing these fluids, and now assess- wells that we trace and image exhibit
ing their ultimate performance. one or more completion optimization
opportunities, in particular, unstimu-
lated pay, understimulated pay, frac-
Gardner: What are the primary services ture height greater than designed,
ProTechnics provides to industry? proppant pack instability, gravel pack
Woodroof: As a member of the Core Laboratories voids, etc. I believe that the StimGun
group of companies, we are all about technology could have a tremendous
the business of reservoir optimization. impact on the two largest members of
ProTechnics particular piece involves this group, unstimulated pay and
completion diagnostics, namely, understimulated pay.
radioactive tracing and spectral GR
imaging, production/completion profil- Gardner: It seems like people are trying to
ing, chemical tracing and flowback
stimulate a lot of pay at one time.
profiling, and interwell tracing and
Are they very successful at it, or is
profiling.
there a lot of room for improvement?
Woodroof: Yes, you are right. There is a lot of
Gardner: About how many tracer logs from pressure on operating engineers to suc-
well stimulations do you think you cessfully complete more pay at a lower
look at in a month? cost. This very often leads to incom-
Woodroof: I analyze or interpret, on average, plete treatment coverage of multiple
about 100 spectral GR images per pay intervals by a single treatment
month. stage. The ultimate result is an under-
performing well.

Gardner: What strikes you in these log

reviews as being areas where the
StimGun technology could be of
benefit?

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StimGun sect 4b 9/19/02 8:53 PM Page 64

Gardner: Are there any certain geographic areas number two, because they are reluctant to
in the U.S. where you consistently rec- spend a few more dollars on the perforat-
ommend people considering the ing side to enhance production down-
StimGun technology? stream. Sadly, the corporate culture in
Woodroof: I probably recommend it most often in some companies does not really encourage
the Rockies, the San Juan Basin, and unconventional completion approaches.
West Texas.

Gardner: Can you name a few places where

you have seen the technology be
When an operator commits
overwhelmingly successful? to a StimGun job, they open
Woodroof: Places as diverse as West Texas, up access to one of the most
Algeria, and offshore Gulf of
Mexico. focused technical teams
Buddy Woodroof
Gardner: Its true that Core Lab owns both
Protechnics and Owen (who is one of
the StimGun partners); does that influ-
Gardner: What other things do you think the
ence your comments?
readers of this booklet should know or
Woodroof: Since ProTechnics entered the spectral GR
consider?
imaging arena in 1996, we have always
Woodroof: When an operator commits to a StimGun
endeavored to provide an answer product,
job, they open up access to one of the
not just a log. Thus, as a part of the
most focused technical teams I have ever
interpretive process, we always attempt to
been associated with, including physi-
make recommendations in our final
cists, petroleum engineers, chemists,
images targeted at optimizing the com-
propulsion experts, completion experts,
pletions. As a part of that process, I was
and pressure monitoring experts. In much
recommending the StimGun technology
the same fashion as we see with techni-
long before Core Laboratories bought
cal spin-offs from the space program,
Owen.
StimGun practitioners will also be
exposed to novel technologies in the areas
Gardner: Why dont you think this technology is of perforating techniques, ultrafast down-
being more widely used by completion hole pressure measurement techniques,
engineers within the industry? computational techniques and formation
damage assessment.
Woodroof: There are two main reasons; number one,
because they are not familiar with it; and

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

Does propellant help or hurt

hydraulic fracturing?
By E. Glynn Williams, Marathon Oil Company

T he intent of hydraulic fracturing is to increase

well productivity. However, in the process of
drilling and preparing the well for fracturing,
many activities take place that can limit the ulti-
mate success of the job. Initially, drilling creates
mechanical damage and causes restrictions to
inflow by allowing the invasion of drilling mud fil-
trate. To these limiting activities, damage is added
to the formation by pumping cement into the
annulus behind the casing. Finally, perforation,
probably the most damaging treatment of all, is
added to the above effects.
Depicted in Figure 1, the perforating event is
usually conducted using an explosive jet perfora- Figure 1 Initial perforating event.
tor. This device creates a tremendous force that lit-
erally pushes its way through the steel of the cas-
ing, through the cement, and finally into the for-
mation rock itself. Where did all the material go
that was present just milliseconds before the per-
forating event took place?
Examination of the casing shows that much of the
steel was displaced laterally around each perforation
hole thereby increasing the local thickness of the
steel. The cement and the formation rock are dis-
placed similarly but to a lesser degree. Laboratory
experiments have shown that most of the cement is
displaced, pulverized, and redistributed along the
perforation tunnel and into the rock matrix immedi-
ately surrounding the perforation. Figure 2 Ideal perforation tunnel.
The formation rock apparently reacts similarly, and
also is strongly compacted (densified). In the litera-
ture, this damage is described as the crushed zone
around the perforation. The result is a 40% to 100%
reduction in permeability around the perforation.
When the well is subsequently hydraulically frac-
tured, some lab work indicates that the induced
fractures may not start from the perforation tun-
nels but instead propagate upward and down-
ward through a path-of-least-resistance which may
be in the area between the cement sheath and
the formation, as shown in Figure 3. The frac fluid
continues along this opened path until it finds a
weak spot in the formation rock and then turns
again as it starts the formation fracture. This is one Figure 3 Diverted hydraulic fracture initiation.

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StimGun assembly generates much less pressure, but

still a considerable amount in a relatively longer time
frame and over a broader area in the perforation tun-
nel. It has been well-documented that fracture initia-
tion pressures tend to be lower in wells that have
used the StimGun process. It is theorized and sup-
ported by surface experiments that the pressurized
gas generated breaks down the perfs and creates frac-
tures through the crushed zone. See Figure 4. By exit-
ing the wellbore through the perforations and contin-
uing down the perforation tunnel without having to
make multiple turns the pressure required to initiate,
extend, and maintain a hydraulic fracture is less for a
given flow rate.
Figure 4 Ideal fracture initiation from perforation tunnel. The only detriment of using a StimGun assembly
would be if there were any contaminates in the well-
cause of near-wellbore tortuosity, which increases bore fluids. The gas from the StimGun burn mixes
treatment pressure, restricts flow, and leads to prema- with the formation fluids and can push the contami-
ture sand-outs. nants into the perforations. This would add to the
The perforating event generates millions of pounds already present damage. However, this type of dam-
per square inch of pressure at the jet tip and lasts age should be overcome by the hydraulic fracture
micro-seconds. The following propellant burn of the stimulation.

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

An overview of SPE paper 63104:

new techniques for hydraulic
fracturing in the Hassi Messaoud
field
Kent Folse, Halliburton Energy Services

H alliburton obtained the first commercial

license to the StimGun assembly technology
and currently runs the largest amount of propel-
initial re-perforating efforts did not significantly
improve injection, the StimTube tool was utilized
to break down perforations to increase injection
lant in the world. One of the approaches this rates and allow hydraulic fracturing to occur. In the
company has taken to lend technical credibility to very first StimTube tool application, a four-fold
the technology is through the publication of SPE injectivity improvement was noted.
papers. Among such papers that have been pub- A fracture stimulation was then effectively
lished is, SPE paper 63104: New Techniques for placed in this well (52,000 lbs (23,600 kg) 20/40)
Hydraulic Fracturing in the Hassi Messaoud Field, without operational problems.
written by Diederik van Batenburg, Halliburton;
In subsequent wells similarly treated, radioactive
Bachir Ben Amor and Rafik Belhaouas, Sonotrach,
tracer logs verified that the fracturing fluids effec-
and presented at the SPE Annual Technical
tively exited the wellbore where the propellant
Conference in Dallas, October 2000. This paper is
stimulation was placed, even though other perfo-
a fine example of the successful use of the
rated intervals existed in the well.
StimGun assembly technology to improve perfo-
ration breakdown and hydraulic fracturing. The This is just one paper describing three case histo-
entire technical paper, with due recognition to the ries. Well over a hundred other examples exist
SPE for allowing its republication, is included in where the StimGun family of products has aided
the Appendix. the ability to hydraulically fracture the formation.
Individuals unfamiliar with the technology who
Summary overview have never used it believe that the ability to
In Algeria, an operator was having a great deal hydraulically fracture a well will be reduced if pro-
of difficulty fracture stimulating some of the wells pellants are utilized; in fact, all the field results
conventionally perforated at well depths of about show just the opposite. Concerns about adverse
11,155 ft (3400 m). One of the primary reasons effects of multiple fractures and excess leak-off
some of the wells could not be fracture stimulat- have proven to be unfounded. Instead, it appears
ed was that treating pressures were too high and that propellant treatments reduce treating pres-
corresponding injection rates were too low. After sures and improve fracture fluid flow.

After StimTube
Before After Re-perforating
Tool Breakdown

8 BPM (1.3 m /min)

3
10 BPM (1.6 m /min)
3
38 BPM (6 m /min)
3

injection at injection at injection at

9500 psi (66 MPa) 9000 psi (62 MPa) 9300 psi (64 MPa)

Fracture fluid injection rates and pressures on an Algerian well before and after using StimTube tool.

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Improving hydraulic fracturing

effectiveness by wireline StimGun
assembly perforating in the San
Andres formation of West Texas
Kevin Miller, Marathon Oil Company

T his article is a case history of the StimGun

assembly assisting in the breakdown of San
Andres formation perforations. This perforation
sleeve that slides over a conventional perforating cas-
ing gun and generates a rapidly expanding gas force
upon gun detonation (Figure 1). Perforating, acid
breakdown method improves the vertical coverage of breakdowns, hydraulic fracturing and radioactive
stimulation fluids. The method was used following tracer work done in conjunction with the jobs are
work on three wells that utilized conventional meth- reviewed. Comparisons are made with the three off-
ods of breaking down perforations prior to sand frac- set wells in the same formations.
turing. The new method was tried because of the
inability of the sand fracture treatment to enter all Background
perforations, leaving a portion of the San Andres The wells discussed in this article are a part of the
unstimulated. All of the determinations were based development of a waterflood expansion located in
on radioactive tracing of the fracture fluids and the the Howard Glasscock Field in Howard County,
resultant after-fracture log. Texas. The expansion involves waterflooding the
The StimGun technique employs a propellant Glorieta, Clearfork, San Andres, Queen and Seven

Looking through the interior diameter (ID) of a propellant Side view of propellant sleeve.
sleeve.

Sliding propellant sleeve over perforating gun. Lifting StimGun assembly on an electric line job.
Figure 1 This is an excellent case history where propellant improved fracture stimulation. Screen-outs were
eliminated and larger proppant was placed in the pay zone. The above pictures show the typical tools used on a job.

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

12,000
Perforation
Event Overlay of Pressure Response
10,000
0

8,000
0
Run #2
Pressure - psi

Run #1

6,000
Run #3 Run #4

Propellant Ignition
Gas Expansion
4,000
0

2,000
0

0
0 0.005 0.01 0.015 0.02 0.025
Ti
Tim seconds

Figure 2 Pressure vs. time overlay of four StimGun assembly runs for perforation breakdown in a West Texas well.
Runs 1 and 2 are in the same interval; runs 3 and 4 are in a different interval.

Reflected pressure wave

from bridge plug

Figure 3 PulsFrac model Run no. 1 Figure 4 PulsFrac model Run no. 2

Figure 5 PulsFrac model Run No. 3 Figure 6 PulsFrac model Run no. 4

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StimGun sect 4b 9/19/02 8:53 PM Page 70

Figure 7 Heusinger Figure 8 Price Scott No. 7, with- Figure 9 R.C. Scott No. 30, with-
No. 11, without out StimGun treatment out StimGun treatment
StimGun treatment

Figure 10 Heusinger No. 25, with StimGun treatment, showing

improved zonal coverage.

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

Rivers formations and includes the development of whether all perforated intervals had been broken
waterflood patterns for these formations. The water- down and accepted fracture fluid. The tracer
flood was being developed on 10 acre results are shown in Figures 7-9. The tracer profiles
(0.4 hectares) patterns with multiple reservoir indicate that in all three wells, the fracture treat-
completions. It was therefore critical to adequately ment did not stimulate all of the perforated inter-
stimulate all intervals for the development of verti- vals. In addition, two of the three fractures had pre-
cal conformance in both producers and injectors. mature screen-outs during the final two stages.
The primary stimulation of the producing well
Job design and implementation
intervals was sand fractured. The injection well
intervals were being acidized instead of sand frac- Because of the potential for premature screen-
tured to minimize communication between injec- out and for inadequate stimulation of all San
tors and producers and to reduce vertical commu- Andres intervals, an improved method of perfora-
nication within an individual wellbore. tion breakdown was sought. The method chosen
was to use the StimGun assembly prior to acid
The StimGun assembly is a combination of a
breakdown and fracture stimulation.
conventional scalloped perforating gun and a pro-
pellant sleeve. The technology utilizes a propellant The stimulation design was utilizing PulsFrac
that provides high pressure gas upon detonation computer software to model the creation of frac-
which dynamically fractures the adjacent rock. tures and to define the propellant sleeve choice.
This high pressure gas creates enough short-term The inputs for this model included wellbore and
pressure to provide dynamic fracturing without formation information. The model calculates the
creating enough pressure to damage the rock as number of fractures created from the energy of the
with the use of explosives. The pressure event has propellant burn and the corresponding fracture
a duration of milliseconds and has a desirable length. Model output also provides an indication
maximum value of two to three times the fracture of the propellant burn characteristics based on the
initiation pressure of the rock. The generated gas output of the pressure vs. time curve shape.
volume and subsequent gas pressure produces The equipment required to do this work includ-
ed 338 in. (85.7 mm) inside
diameter (ID) by 4 in.
The technology utilizes a propellant (101.6 mm) outside diameter
that provides high pressure gas upon (OD) propellant sleeves,
338 in. (85.7 mm) scalloped
detonation, which dynamically perforating guns, deep pene-
fractures the adjacent rock. trating 23 gram (gm) perfo-
rating charges, and high-
speed pressure gauges. The
two to six short fractures adjacent to and emanat- perforating guns were loaded to perforate at
ing from each perforation plane. 6 shots per foot (spf) (20 spm) with 60 phasing.
The propellant sleeve was slid over the perforating
Offset wells completion methodology and
gun and secured by means of retaining rings. The
problems
high-speed pressure recording assembly was
Prior to StimGun treatment, three wells were screwed into the bottom of the perforating gun.
completed in multiple San Andres intervals fol-
The perforating was done in four runs with very
lowing the same basic procedure: Conventional
good pressure data obtained from each run
perforating, acidizing with 15% HCI acid for per-
(Figure 2). The well was acidized and fracture
foration breakdown, followed by fracture stimula-
stimulated in the same manner as the other three
tion. Two of the wells utilized ball sealers for
wells. The fracture pad and proppant laden fluids
diversion while the final one was acidized using a
were radioactively traced.
selective injection packer system.
In each case, the fracture stimulation included Pressure and model analysis
radioactive tracer material to determine the extent The results of this work were compared with a
of near-wellbore fracture height development and dynamic fracture model to show how well the

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multiple San Andres intervals were stimulated com- reveals adequate near-wellbore proppant placement
pared to offset wells. With respect to production (Sb-124 and Ir-192 tracers) across the upper and mid-
rates, short-term production numbers indicate there dle perforated intervals, but there was barely a mono-
was a measurable improvement in oil production. A layer of proppant placement across the lower-most
sustained, quantitative comparison could not be perforated interval. This lower-most perforated interval
made as all of the wells were shortly commingled would be classified as understimulated, based upon
with other intervals. the minimal proppant placement and resultant low
A composite of the pressure data for all four computed near-wellbore propped width and sand
StimGun assembly runs are shown in Figure 2.
The pressure measurements from the high-speed
gauge for this well were input into the PulsFrac The PulsFrac software
software to estimate the fracturing created by the
propellant-assisted perforating.
is capable of calculating
The PulsFrac software outputs for the four perfo-
pressure waves at great
rating runs are exhibited in Figures 3-6. The peak distances from the
pressure generated by the propellant burn was
9325 psig (64 MPa) for runs 1 and 2 and 9202 psig
perforations.
(63 MPa) for runs 3 and 4. The output of the
concentration. Downward vectoring of proppant
PulsFrac software simulation model indicates that the
below the lower-most perforated interval also likely
propellant produced two fractures in each interval as
contributed to this understimulated condition.
designated by N^. These fractures, designated by L^,
have half lengths of 4 ft to 7 ft (1.2 m to 2.1 m). Offset well 2

The PulsFrac software is capable of calculating The San Andres zone in the Price Scott No. 7 was
pressure waves at great distances from the perfora- perforated in three intervals from 1990 ft to 2080 ft
tions. The pressure data from run 1 (Figure 3) shows (607 m to 634 m). StimGun assembly was not used.
a pressure calculation of greater than 13,000 psi The zone was fractured with a crosslinked gel at 21 bpm
(90 MPa) at 0.05 s. This pressure is being reflected (3.3 m3/min) and 1550 psig, pumping only 16,000 lbs
from a plug back located at 2370 ft (722 m). This (7257.5 kg) of 12/20 Brady sand before screening out.
pressure reflection was recorded in each perforating The tracer image shown in Figure 8 reveals adequate
run, but at a longer time from the propellant event. near-wellbore proppant placement (Sc-46 tracer)
This indicated that the plug back TD was moving across the lower-most perforated interval, but again
further away from the perforating gun with each barely a monolayer of proppant across the upper and
perforating run. The plug back was a retrievable middle perforated intervals. These upper and middle
bridge plug with 50 ft (15.2 m) of sand above. perforated intervals would be classified as somewhat
Upon attempting to retrieve this bridge plug, it was understimulated, based upon the minimal proppant
discovered to have moved 445 ft (136 m) down- placement and resultant low computed near-wellbore
hole. The sand was cleaned off and the bridge plug propped width and sand concentration.
was retrieved and examined. The top set of slips had Offset well 3
been broken off. The San Andres zone in the R. C. Scott No. 30 was
Radioactive tracer comparisons perforated in three intervals from 2026 ft to 2124 ft
(618 m to 647 m). StimGun assembly was not used.
Offset well 1
The zone was fraced with a crosslinked gel at 32 bpm
The San Andres zone in the Heusinger No. 11 (5.2 m3/min) and 4150 psig (29 MPa), pumping
was perforated 4 spf (13 spm), 120 phased in three 53,000 lbs (24,000 kg) of 12/20 Brady sand to com-
intervals from 2032 ft to 2113 ft (619 m to 644 m). pletion. The tracer image shown in Figure 9 reveals
StimGun assembly was not used. The zone was modest to marginal near-wellbore proppant placement
fraced with a crosslinked gel at 33 bpm (Sb-124 and Ir-192 tracers) across the upper-most per-
(5.2 m3/min) and 3000 psig (21 MPa), pumping forated interval and a monolayer at best of proppant
29,900 lbs (13,600 kg) of 12/20 Brady sand before placement across the middle and lower perforated
screening out. The tracer image shown in Figure 7 intervals. These middle and lower perforated intervals

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would be classified as understimulated, based From this work, Marathons Midland

upon the minimal proppant placement and result-
office concluded:
ant low computed near-wellbore propped width
and sand concentration. This zone remains under- Breakdown of perforations can be accom-
stimulated despite pumping the fracture treat- plished by propellant-assisted perforating.
ment to completion. Propellant-assisted perforating is beneficial in
StimGun assembly well with perforation adequately breaking down all perforations,
which enables stimulations to be effective in all
breakdown
perforated intervals.
The San Andres zone in the Heusinger No. 25
The stimulation results indicate that there was
was perforated 6 spf (20 spm), 60 phased
no damage to the casing or formation due to
changes. StimGun assembly was used in these
the energy developed by the propellant.
two intervals from 2204 ft to 2144 ft (672 m to
653 m). The zone was fraced with a crosslinked gel The creation of fractures from the propellant
at 32 bpm (5.2 m3/min) and 3000 psig (21 MPa), did not adversely affect the ability to hydrauli-
cally fracture the formation.
pumping 52,000 lb (23,600 kg) of 12/20 Brady
sand to completion. The tracer image shown in If a comparison of procedures is desired, then
Figure 10 reveals adequate near-wellbore proppant adequate planning should be done to ensure
placement (Sb-124 and Ir-192 tracers) across both proper testing is performed to obtain the nec-
perforated intervals, despite downward vectoring essary data.
of proppant below the lower perforated interval. In-hole modeling of pressure responses should
Overall, StimGun treating Heusinger No. 25 be performed to adequately predict forces
within the wellbore which may affect equip-
exhibits much more uniform and more complete
ment such as packers and plug back devices.
proppant coverage of the perforated intervals. By
simultaneously perforating and breaking down Plug back equipment needs to be developed
each interval, the propellant-assisted perforating to adequately withstand the forces created by
technique appears to have improved the uniformi- propellants.
ty of proppant placement as reflected in the com- Radioactive tracers provide an excellent
parison of the tracer profiles. method of identifying stimulation profiles.
The fast pressure data have been recognized as
useful data for rock properties evaluation, and
the use of these data for rigorous evaluations
should be pursued.

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Underbalanced TCP StimGun

assembly applications to obtain initial
production and improve hydraulic
fracturing
Jim Gilliat, Canadian Completions Services The Expro Group

P etromet Resources Ltd., Calgary Alberta, a

Canadian Oil & Gas producer, approached
Canadian Completion Services for a recommendation
on a well completion in the foothills of the Rocky
Mountains in Western Alberta.
Historically, the Cadomin formation has been diffi-
cult to produce. In the foothills of this area of the
Rocky Mountains, tectonic stresses can create prob-
lems with tortuosity and pre-mature screen-outs. The
formation requires hydraulic fracturing in order to be
economically viable. In many cases as a pre-treat-
ment a process called extreme overbalance (EOB) Figure 2 Gas expansion of the burning propellant sleeve
as the formation is fractured.
perforating is used to break down the perforations
and initiate the fractures. This technique uses a col- The StimGun assembly is a process licensed from
umn of nitrogen and a small amount of liquid in the Marathon Oil Company involving the use of an
tubing which is pressured up in excess of the fracture oxidizer and resin propellant mixtures molded into
gradient of the formation. When the perforating gun a tube that is fitted over a perforating gun, as illus-
fires, the fluid and nitrogen rush toward the forma- trated in Figure 1.
tion at a very high velocity, surging open the perfora- When the perforating gun detonates, heat and
tions and initiating a small fracture. shock created by this event ignites the propellant
In this well, Petromet Wild River, existing perfora- sleeve, generating a large volume of gas at very high
tions above the zone of interest made the EOB tech- pressure, which is directed into the perforations, as
nique impractical. The StimGun assembly was rec- illustrated in Figure 2.
ommended as an alternate to achieve formation This gas pulse can generate pressures as high as
breakdown. 20,000 psi (138 MPa) for 15 to 250 milliseconds.
The result in most cases is rapid perforation break-
down and the initiation of a fracture near the well-
bore. The spent gas can then be used to flow back
debris from immediately around the wellbore.
What was unique about the Petromet job was the
fact that the StimGun assembly was combined with
underbalanced tubing-conveyed perforating (TCP) to
enhance well results.
The tool assembly that was run is illustrated in
Figure 3. A surge tool was run to keep a pre-deter-
mined fluid level in the tubing in order to create a
3000 psi (21 MPa) draw-down on the formation. Once
Figure 1 StimGun assembly: The perforating event
the bottom hole assembly was logged into position,
ignites an outer propellant sleeve as it perforates the casing
and formation. the packer set, and the wellhead installed, a firing bar

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

which was dropped from the surface detonated the

perforating gun. The firing bar also broke a glass Radioactive
disc in the surge tool allowing communication marker
between the tubing and the annulus below the
packer.
When the gun fired, the propellant ignited as
described above, surging the perforations and ini-
tiating a bi-wing fracture. Once the initial surge
from the StimGun assembly sleeve had dissipat-
ed, the high underbalance pressure from the reser-
voir backsurged into the wellbore, helping to fur-
ther clean up near-wellbore perforating and
drilling damage. A split second later the gun dis-
connected itself from the bottom hole assembly, Retrievable
packer
leaving full-bore tubing for the hydraulic fracture.
The end result of the StimGun treatment was a
near classic hydraulic fracture job. Typically break-
down pressures in this field may exceed the fracture
gradient of the formation by 3000 to 4000 psi
(21 to 28 MPa) before the formation breaks and
the actual hydraulic fracture begins. In this Wild
River well, no formation break was noted; sand was
pumped into the zone at fracture pressure. The end
result was 30% less pumping horsepower was
required during the treatment; the calculated frac-
ture gradient of the well was 7900 psi (55 MPa). As
illustrated on the graphs (Figure 4) the pumping
operation begins at 7900 psi (55 MPa) and contin-
ues until screen-out. In all, 55,100 lbs. (25,000 kgs)
of proppant were placed in the formation.
Surge tool
The customer was very happy that a potential
problem was eliminated and, as a result of the
StimGun assembly a better well completion was
achieved.

Mechanical firing head with

automatic release

Perforating gun with

StimGun propellant sleeve

Figure 3 Tool assembly run on the Petromet StimGun

TCP underbalanced job.

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FracCAT*
70
Pressure - MPa (megapascals)

60

50
TR Press
40 TR Press
30 AN Press
20
AN Press
10

0
00.00.00

Slurry Rate
Cubic Meters per Minute

Slurry Rate

00

100
Prop Con
BH Prop Con
Kilograms per Cubic Meter

Prop Con

50
BH Prop Con

00
Time Minutes

*Schlumberger Dowell 1994-96

Figure 4 Fracture graph from the Petromet Wild River job where an underbalanced tubing-conveyed perforating (TCP)
StimGun assembly was used. Typical jobs in the area showed a 3000 to 4000 psi (21 to 28 MPa) spike prior to break-
down. In this case the sand went into the formation at the calculated fracture pressure of 7900 psi (55 MPa).

* FracCAT is a mark of Schlumberger Dowell

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An overview of SPE paper 71639:

Field performance of
propellant/perforating technologies
to enhance placement of proppant
on high-risk sand-control
completions
Kent Folse, Halliburton Energy Services

D eveloping new applications for the StimGun

assembly has been a priority. Typically, a new
application will increase well productivity or
scenario could improve proppant placement, cost
efficiency, and safety.
The entire SPE paper 71639 is included in the
reduce costs. Halliburton, with customer assis- Appendix with due recognition to the Society of
tance, has successfully developed a new applica- Petroleum Engineers for allowing its republication.
tion for improving frac-and-pack treatments that
improves production, reduces costs, and increases
safety. SPE paper 71639: Field Performance
of Propellant/Perforating Technologies to
Enhance Placement of Proppant on High
Risk Sand-Control Completions by Kent C.
Folse, Richard L. Dupont, and Catherine G.
Coats, SPE, Halliburton Energy Services, Inc.,
David B. Nasse, Shell Offshore, Inc. present-
ed at the 2001 SPE Annual Technical
Conference in New Orleans, Louisiana, is an
excellent example of the benefits for cus-
tomers of assisting in the development of
new applications.
Traditionally, proper frac-and-pack prop-
pant/sand placement was difficult in uncon-
solidated formations with long, highly devi-
ated, highly laminated intervals with
extreme permeability variations. To ensure
that the low permeability intervals accept
fracturing fluids and proppant during treat-
ment, a Gulf of Mexico operator used the
StimGun assembly to break down the per-
forations prior to the fracturing treatment.
The tubing-conveyed perforating jobs were
completed in a balanced condition with
only the lower quality intervals being stimu-
lated with the StimGun assembly. Two very
detailed case studies are presented in the
technical paper. It was concluded that com-
bining propellant/perforating in a balanced Spectral gamma ray log documenting improved proppant placement.

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Propellant assisted perforation

breakdown examples
David Cuthill, Computalog Wireline Services

P ropellant stimulations are designed to comple-

ment current completion and workover methods.
Applying a controlled dynamic pulse of high pressure
burns, high-pressure combustion gases are generated.
These gases mix with the wellbore fluids and the result-
ing energetic mixture is injected into the perforation tun-
gas can break down and clean up the perforation nels. As the pressure increases, strain energy is accumu-
tunnel, initiate and extend fractures perpendicular to lated in the rock matrix around the perforations until
the wellbore, and back flush the near-wellbore area fracturing is initiated. Fracture growth is maintained by
to ensure an unobstructed flow from the reservoir continued gas generation from the tool burn. In some
into the wellbore. By initiating fractures and clean- cases, after the tool is spent, the flow may reverse and
ing-up the near-wellbore area, perforations are made there may be a back-flushing effect which aids clean
more effective and more receptive to hydraulic frac- up of the near-wellbore area. The degree of back-
ture stimulation. flushing is dependent on a number of factors but is
Routinely, propellant stimulation devices, such as the primarily dictated by the type and height of the tamp
StimGun assembly, StimTube tool, and WST, are fluid. The potential for back-flushing increases by
used for near-wellbore cleanup and enhancement. decreasing the volume and compressibility of the
One of the primary applications is for perforation tamp fluid.
breakdown and fracture initiation. Propellant stimula- When a StimGun assembly is used in a newly per-
tion has been effective after an unsuccessful hydraulic forated well completion, the basic mechanism is
identical to the stand-alone propellant tools
with the unique difference that the clean up
the StimGun assembly and fracture-causing event begins at the time
permits formation clean up of perforating. Once positioned on depth, det-
onating the shaped charge contained within
in preparation for other the perforating carrier forms the jet which exits
stimulations the carrier and penetrates the propellant sleeve
and the casing, ultimately forming a perfora-
fracturing attempt where formation breakdown was tion tunnel in the formation. The propellant is ignited
not achieved. Propellant is used to initiate formation by the shock and heat of the jet as well as the residual
breakdown, allowing a successful fracturing reattempt pressurization after the charge energy is released. The
at lower initiation pressures. Using propellant at the StimGun treatment can be performed underbalanced
time of perforating through the StimGun assembly to ensure a back surge.
permits formation cleanup in preparation for other
Pressure data
stimulations, or in the case of limited near-wellbore
damage with otherwise good permeability, may elimi- When a high-speed downhole pressure gauge is used,
nate the need for additional stimulation. This should a graphical representation of the stimulation event can
encourage operators to utilize propellant for perfora- be generated for analysis. With the help of software such
tion breakdown initially, rather than after a pump-in as the PulsFrac program, the analysis can help deter-
failure has occurred. mine the effect of the stimulation on the formation and
evaluate the burn of the propellant. In some cases where
Mechanism a sufficiently long sequence of noise-free data are avail-
In a previously perforating well the propellant tool able, the pressure profile can be related to the reservoir
may be a WST or a StimTube tool as additional perfo- properties. For example, an estimate of fracture closure
rations are normally not required. This tool is typically pressure can be observed in the data by analyzing the
deployed on wireline or tubing, positioned over the pressure leak-off response using a Nolte G-function or
perforated interval, and ignited. As the propellant rapidly similar plot.

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Selected case histories breakdown case histories shown below are a small
Use of the StimGun technology for perforation sampling of the jobs performed using the
breakdown has had an approximate 95% histori- StimGun technology. These examples show vari-
cal success rate. The following selected perforation ous approaches to meeting the operators require-
ments and the resulting positive outcomes.

Case 1
Objective: Client attempted to fracture down the casing for economic reasons. Fracture breakdown
could not be obtained after pumping up to casing yield pressure.
Solution: A WST tool was proposed as a method of breaking down the perforations and to initiate
formation breakdown.
Configuration:
Orientation: Vertical
Formation: Ostracod sandstone; 7349 ft (2240 m)
Casing size: 512 in. (139.7 mm)
Tool: 2 in. (50.8 mm) WST propellant, conveyed on wireline
Tamp: Aquamaster 12
Results: Successfully pumped a 13,000 lb (6 tonne) fracture with breakdown at 5200 psi
(36 MPa) breakdown, approximately 580 psi (4 MPa) less than expected. Allowed well
to be fractured down the casing which lowered pumping pressure and costs. After the
fracture, the well was brought onto production at a rate of 82 bpd (13 m3/d), oil.

Case 2

Objective: Client attempted to fracture well and could not obtain a feed rate. Interval was reperfo-
rated at a higher shot density and fracture reattempted with no success.

Solution: A WST tool was proposed as a method of breaking down the perforations and to initiate
formation breakdown.

Configuration:
Orientation: Vertical
Formation: Halfway dolomitic sandstone; 7349 ft (1635 m )
Casing size: 512 in. (139.7 mm)
Tool: 2 in. (50.8 mm) WST propellant, conveyed on wireline
Tamp: Frac fluid to surface

Results: After ignition of propellant tool, well immediately went on vacuum and was subsequent-
ly fractured successfully. The breakdown pressure was lowered to an acceptable level.

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Case 3

Objective: Client needed to fracture into select areas of the horizontal open hole leg of the well.
Hydraulically fracturing an open hole horizontal well is challenging because it is difficult to
selectively localize the stimulation.

Solution: A WST tool was proposed as a method of selectively generating a weak point at two
6.56 ft (2 m) intervals in the horizontal leg.
Configuration:
Orientation: Horizontal
Formation: Doig sandstone; 4265 ft (~1300 mTVD)
Casing size: 6.25 in. (155.6 mm) Open Hole completion
Tool: 2.5 in. (63.5 mm) WST propellant, conveyed on tubing

Tamp: Cutter D produced fluid

Results: After running propellant tools, the well was successfully fractured in the two intervals. A 40%
reduction in predicted breakdown pressure was observed.

Case 4

Objective: Drill stem testing indicated that the completion interval had a significant skin. An underlying
water zone did not permit a hydraulic fracture. Client needed a localized stimulation to avoid
connecting with water.
Solution: A WST tool was proposed as a method of stimulating the near-wellbore without going out of
zone.
Configuration:
Orientation: Vertical
Formation: Kiskatinaw sandstone; 6100 ft (1850 m)
Casing size: 5.5 in. (139.7 mm)
Tool: 2 in. (50.8 mm) WST propellant conveyed on wireline
Tamp: Killsol solvent
Results: After running propellant tools, the fluid level rose 656 ft (200 m) and the well had to be killed
to run pipe. The propellant successfully cleaned up the near-wellbore region without connect-
ing to the water zone.

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Case 5
Objective: Client required a perforating system that would compliment a proposed hydraulic frac-
turing operation.
Solution: A StimGun assembly was proposed to clean up and break down the perforations. The
system was run on tubing because multiple intervals were completed.
Configuration:
Orientation: Vertical
Formation: Morrow sandstone; 11,025 ft (3360 m)
Casing size: 5.5 in. (139.7 mm)
Tool: 4.13 in. (104.8 mm) propellant sleeve over 3.38 in. (86 mm) expendable retrievable
hollow steel carrier (ERHSC) loaded at 6 spf (20 spm) & 60 phasing.
Tamp: Produced water
Results: After perforating, the well flowed gas to surface. Production was achieved without fur-
ther stimulation that would normally have been required. Zone proved to be wet. Client
determined that significant savings were realized by determining this early.

Case 6
Objective: Client required a perforating system that would avoid the need for a hydraulic fracture
and provide better connectivity to the reservoir as completion interval was close to
water.
Solution: A StimGun assembly was proposed to clean up and break down the perforations. The
system was run under a 1000 psi (7 MPa) nitrogen head to provide confinement and
efficient propellant burn due to low fluid column over tool.
Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1150 ft (350 m)
Casing size: 5.5 in. (139.7 mm)
Tool: 4.13 in. (104.8 mm) propellant sleeve over 3.38 in. (86 mm) ERHSC loaded at 6 spf
(20 spm) & 60 phasing.
Tamp: KCl water
Results: After perforating, the well flowed gas to surface at a sustained rate of 225 mcf/d
(6.5 E3m3/d) with no observed water production. This production rate is considered
good for this area and depth.

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Case 7

Objective: Client had poor results with hydraulic fracturing (premature sand-off and unset packers). Had
observed good success with extreme overbalanced perforating to achieve near-wellbore
cleanup but required a lower cost alternative.

Solution: A StimGun assembly was proposed as a lower-cost alternative to near-wellbore cleanup.

Configuration:
Orientation: Vertical
Formation: Bakken sandstone; 2840 ft (865 m)
Casing size: 5.5 in. (139.7 mm)
Tool: 4.13 in. (104.8 mm) propellant sleeve over 3.38 in. (86 mm) ERHSC loaded at 4 spf (13 spm)
& 90 phasing with a 26 g big hole (BH) perforation charge.
Tamp: Produced water

Results: The well responded the same as had been observed when using extreme overbalanced perfo-
rating. The well went onto pump without need for additional cleanup or stimulation. The
client wanted to use a big-hole charge, but there was concern about getting past near-well-
bore damage due to reduced charge penetration. By using the StimGun assembly, the pro-
pellant was able to break through the near-wellbore damage and connect into the reservoir.

Case 8
Objective: Client had previously attempted a fracture but experienced poor results. A plan was proposed
to attempt to refracture the interval.
Solution: A WST tool was proposed as a method to assist the placement of the refracture.
Configuration:
Orientation: Vertical
Formation: Upper Nikana sandstone; 6693 ft (2040 m)
Casing size: 5.5 in. (139.7 mm)
Tool: 2 in. (50.8 mm) WST propellant tool.
Tamp: Frac oil
Results: After the propellant stimulation, there was an indication of increased productivity. The refrac-
ture attempt was placed more effectively with better overall performance, but the well did not
appear to be viable.

Conclusions a successful fracture reattempt at lower initiation

Ongoing applications have demonstrated the pressures.
need and effectiveness of propellant stimulations Using propellant at the time of perforating
for near-wellbore perforation cleanup. through the StimGun assembly permits
Propellant stimulation is useful after an unsuccess- formation clean up in preparation for other stimu-
ful hydraulic fracture attempt where formation lations, or, in the case of limited near-wellbore
breakdown cannot be safely achieved. The use of damage and good permeability, may eliminate
propellant initiates formation breakdown allowing the need for additional more costly stimulations.

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

Restoring injectivity
Bob Haney, HTH Technical Services, Inc.

W ell injectivity can be reduced by perforation

damage, near-wellbore filtrate problems,
scale, emulsions, etc. The pressure created during
mation-compatible fluid is being injected into the
reservoir, the rates will not be sustained. A well in
Yemen had a 7000 bpd (1113 m3) increase which
propellant stimulation is above the tensile dropped off rapidly to a few hundred bpd when
strength of the formation rock and that of any the pump operator decided to bypass the filters
debris (other than steel) plugging the perfora- because they were plugging. The injection was
tions. This breaks down the perforations, and rap-
restored with a light acid wash. Similar wells in
idly injects a high pressure, turbulent mix of com-
Africa were permanently damaged by the injec-
bustion gases and wellbore fluid into the forma-
tion restoring injectivity. tion of dirty fluid after propellant stimulations.

In numerous examples of successful applica- Propellant stimulation, when combined with

tions, injection rates have increased as much as good field practices, can be a very cost-effective
15,000 bpd (2385 m3) from a single wireline run way to remove near-wellbore damage in injection
of StimTube tools. However, unless a clean, for- wells.

Selected case histories

Case 1

Objective: Restore injectivity in deviated well, avoid possible sidetrack.

Solution: Reperforate with long StimGun assembly (longest run to date on electric wireline).

Configuration:
Orientation: Deviated
Formation: Tofte, 300 md, 9331 to 9476 ft (2844 to 2888 m)
Casing: 7 in. (177.8 mm), 29 lbs (13 kg)
Tool: 144 ft (43.9 m) StimGun assembly with 66 ft (20 m) of propellant

Result: Injection rate increased from 32,700 to 48,400 bpd (5200 to 7700 m3/d).

Case 2
Objective: Avoid regular acid wash and possible fracture.
Solution: Treat with StimTube tool.
Configuration:
Orientation: Vertical
Formation: Dina sand, 40 md, 2755 ft (840 m)
Casing: 5.5 in. (139.7 mm)
Tool: 2.5 in. (63.6 mm) StimTube tool
Result: Injection rate increased from 34 to 500 bpd (5.4 to 80 m3/d) at 1000 psi (7 MPa).

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Case 3
Objective: Improve injectivity where conventional reperforation and fracture did not succeed.
Solution: Reperforate with StimGun assembly followed by light acid wash.
Configuration:
Orientation: Vertical
Formation: Doe Creek sand, 3610 ft (1100 m)
Casing: 5.5 in (139.7 mm)
Tool: StimGun assembly
Result: Injection rate improved from 225 to 380 bpd (36 to 60 m3/d).

Case 4
Objective: Overcome lost injection to thief zone.
Solution: Squeeze and reperforate with StimGun assembly.
Configuration:
Orientation: Vertical
Formation: Grayburg dolomite
Tool: StimGun assembly
Result: Injection rate restored to 900 bpd (143 m3/d), in zone.

Case 5
Objective: Restore injectivity in open hole.
Solution: Run WST.
Configuration:
Orientation: Vertical
Formation: Madison dolomite, high perm
Casing: None
Tool: 2.5 in. (63.5 mm) WST
Result: Injection rate improved by 1800 bpd (286 m3/d).

Case 6
Objective: Improve injection rate.
Solution: Use WST in previously perforated well.
Configuration:
Orientation: Vertical
Formation: Glauconitic sand, 3100 ft (945 m)
Casing: 4.5 in. (114.3 mm)
Tool: 2 in. (50.8 mm) WST
Result: Injection rate increased from 1900 to 4400 bpd (302 to 700 m3/d).

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A p p l i c a t i o n Ty p e : P e r f o r a t i o n B r e a k d o w n

Case 7
Objective: Improve injection rate.
Solution: Use WST in previously perforated well.
Configuration:
Orientation: Vertical
Formation: Quishn sand (Sudan), 5740 ft (1750 m)
Casing: 6 in. (152.4 mm)
Tool: 3 in. (76.2 mm) WST
Result: Injection rate improved from 4500 to 10,000 bpd (715 to 1590 m3/d).

Case 8
Objective: Improve rate in gas injector well.
Solution: Reperforate with StimGun assembly.
Configuration:
Orientation: Vertical
Formation: Viking sandstone
Casing: 5.5 in. (139.7 mm), 3280 ft (1000 m)
Tool: StimGun assembly
Result: Injection rate increased by 225%.

Case 9

Objective: Improve injectivity in wells in Kuwait.

Solution: Reperforate with StimGun assembly.

Configuration:
Orientation: Vertical
Formation:
Casing: 7 in. (177.8 mm)

Tool: 4.625 in. (117.5 mm) gun with 5.25 in. (133.4 mm) StimGun assembly, tubing-con-
veyed

Result: Before treatment, injection rate was 3600 bpd (572 m3/d) through 4 in. (101.6 mm)
tubing at 2000 psi (1.4 MPa). After treatment, rate was 11,500 bpd (1830 m3/d)
through 3 in. (76.2 mm) tubing.

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The first use of specialized

StimGun TCP assemblies for
shallow gas wells was a
successful recompletion in 1998
in the Dakota formation located
in northwest Wyoming.
StimGun sect 4c 9/19/02 8:57 PM Page 87

A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

The first applications of TCP

underbalanced propellant jobs in
shallow Rocky Mountain gas wells
Ralph Affinito, Marathon Oil Company
Larry Staten, Halliburton Energy Services

T his article describes how TCP assemblies were

revised to allow effective use of the StimGun
assembly ignition and immediate subsequent
Completion utilizing the StimGun
assembly
The process leading to an improved completion
underbalance to occur in shallow gas wells. The design:
first use of the technology was a successful recom-
Minimize liquid contact and provide as much
pletion of a gas reservoir in the Dakota formation
stimulation as possible. Reservoir evaluation
located in northwest Wyoming in 1998.
indicated the kaolinite, chlorite, and illite
Historical background mixed layer clays system of the reservoir would
Uphole gas recompletions in the field utilized best be stabilized by use of 3% NH4Cl
cased hole wireline perforating in a balanced con- replacing the KCl system.
dition with 3% KCl water. Economic production The permeability of an undamaged reservoir
after swabbing generally required a breakdown or was thought to be sufficient to allow
proppant fracture treatment. Post-fracture rates production at economic rates without need for
ranged from 300 to 1000 mcfgpd (8500 to fracture stimulation.
280,000 m3/d). This reservoir was generally fault- An adjacent clean sandstone which was water
ed yielding relatively small accumulations of gas prolific also made proppant fracturing too
depleted by less than three wells per fault block. great a risk in this wellbore.
Exploitation was through recompletions from Based upon the low SBHP of the reservoir,
deeper intervals. solely underbalanced perforating would not
Post-breakdown/fracture transient analysis of one yield an adequate completion.
earlier completion indicated 31 md permeability A system of underbalanced TCP in combination
and -3.5 skin. This zone was also extremely sensi- with the StimGun assembly to provide an ade-
tive to fluids, as demonstrated in one Dakota com- quate formation breakdown and near-wellbore
pletion which tested 1000+ mcfgpd following fracturing with minimal fluid contact appeared to
proppant fracture treatment and never returned to be the appropriate approach. The initial concern
an economic production rate following loading the with use of the StimGun assembly was the
hole with completion brine and running tubulars. requirement that 600 psig of liquid hydrostatic
General Reservoir parameters are as follows: tamp exist for the propellant to effectively perform.
The novel approach employed in this applica-
Depth: 1400-1800 ft (427-549 m)
tion, for the first time in industry, was to trap a
Porosity: 17.60% fluid tamp of 600 lbs (4.1 MPa) of hydrostatic pres-
sure below the packer but still have a minimum
Gross pay: 148 ft (45 m)
amount of fluid in the tubing to accommodate the
Net pay: 52 ft (16 m) 325 psi (2.2 MPa) SBHP of the Dakota formation. A
maximum differential bar vent was used to achieve
Water saturation: 26.67% the closed system. The maximum differential bar
SBHP: 325 psig (2.2 MPa) vent was held closed by a chamber of silicone fluid
and a spring. When the detonating bar was
SBHT: 90F (33C) dropped and passed through this specialized vent,

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it sheared a break plug, allowing the silicone fluid to hydrostatic pressure for the propellant to burn on the
escape and enabling the vent to open, communicat- StimGun, while negligible fluid contacted the reser-
ing the perforated interval to the tubing. A choke was voir. The well was immediately flow tested and placed
placed in the break plug to slow down this action to on production following cleanup. This StimGun com-
enable the guns to fire and the propellant to begin pletion practice was executed on four other wells in
ignition while the hydrostatic pressure was still at this Big Horn Basin field from 19981999. Initial pro-
600 psi (4.1 MPa). This approach worked very well, duction rates ranged from 800 mcfgpd to
and the job was successful. Additionally, the only fluid
4500 mcfgpd (23,700 m3/d to 127,400 m3/d) with
able to contact the perfs when the StimGuns were
the average being 2300 mcfgpd (65,100 m3/d).
fired was 3% NH4Cl. A diagram of a typical comple-
These resulted in higher production rates than older
tion of this type is shown below.
completions and lower capital costs due to removing
Results the necessity to use proppant fracture stimulation.
The StimGun completion in this well performed as This methodology has now been applied to numer-
designed. The bar vent established the necessary ous wells throughout the world.

Dry tubing

Radioactive marker
Water

Halliburton PLS pkr @ 1335 ft (407 m)

Maximum differential Water (KCl fluid)

bar vent and drop
bar firing head

Gross perforations from 1444 to 1592 ft (440 to 485 m)

with 52 ft (16 m) of net perforations

Cement retainer @ 1610 ft (491 m) with 5 sks cmt

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

High-speed gauge data improves

job success on wireline-conveyed
near-wellbore stimulations
Todd McAleese, Marathon Canada, Ltd.

T his article describes the value of understanding

and revising job designs by use of the high-
speed pressure gauges. Production on this exam-
cover the zone. As per standard practice in a new
area at the time, it was decided to use StimGun
assembly, with 50% sleeve coverage. high-speed
ple well was tripled using the StimGun assembly. gauges were used to obtain actual pressure data
After the first run, changes were made on location and allow subsequent runs to be optimized. The
using the gauge data. well was thought to have sufficient hydrostatic
available to ensure the proper burn of the propel-
Before Stimulation: 17 BOPD (2.7 m3/d) lant tools.
After Stimulation: 48 BOPD (7.7 m3/d) After successfully perforating the well on the first
run, the gauge data were downloaded and the
Marathon desired to perform an electric line re- pressure data were reviewed on site. It was found
perforating job on an older rod pumped well in that there was much less hydrostatic than originally
Canada. The Pekisko formation in this well had thought, most likely due to the gassy nature of the
been originally completed in the 1970s. Production fluid, and there was much more produced oil in
had steadily fallen off over the years to the point the wellbore. The pressure curve (see Figure 1,
that the well was becoming uneconomic. The well Run 1) showed only a peak pressure of 8000 psi
was scheduled for a pump change, and it was (55 MPa) was achieved, much less than the com-
elected to re-perforate the zone using the puter model prediction of 13,500 psi (93 MPa)
StimGun assembly. Two runs were required to based on less compressible fluid. Burn time

50
Marathon Canada well

40
Pressure - MPa

30
-- run #2 10.1 MPa hydrostatic 75 % coverage

20

10 -- run #1 5.1 MPa Hydrostatic 60% coverage

0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time - seconds
Figure 1 Using gauge data from Run 1, the operator greatly increased the effectiveness of the propellant burn by
increasing the fluid tamp and propellant coverage, shown in Run 2.

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appeared to be in the range of 45 ms, much longer of the improved job design (see Figure 1, Run 2). By
than originally expected. Long burn times and low increasing the hydrostatic in the wellbore assembly
peak pressure are generally indicators that the hydro- to roughly 900 psi (6.2 MPa), and increasing the
static pressure is too low. The StimGun assembly StimGun sleeve coverage to 75%, the peak pressure
requires confinement to burn properly, and high gas generated at the perforations increased to 13,000 psi
content of the well fluids caused the propellant gases
(89.6 MPa). Burn time was reduced to 25 ms, all
to follow the path of least resistance and pressure up
good indicators that the StimGun assembly sleeves
the wellbore rather than leak off to the formation. Fluid
was added to increase the hydrostatic in the well. The had burned properly.
decision was also made to increase the coverage of Marathon had expected the well to produce at
StimGun propellant to 75% on the second run. 17 bopd (3 m3/d); instead the well came in at
The second perforating run was performed without 48 bopd (7 m3/d) and barely declined over the next
incident, and the gauge data showed clear indication several months.

Over 2000 successful StimGun technology jobs in Western Canada

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

Combining StimGun assembly with

EOB perforation and acid stimulation
significantly improves New York
states gas production
Craig Smith, The Expro Group (formerly with Halliburton Energy Services, Inc.)

E xtreme overbalanced
(EOB) StimGun assembly
jobs completed on the Black
River/Trenton zone in New
York state have proved to be
very successful. This zone is
dolomitic with considerable joints and
fractures. Conventional completion techniques
have rendered less than desired results. Typically
operators perforated with wireline, then attempted
high-rate acid/fracture jobs. The leak-off associated
with the joints and fractures lead to screen-out,
even with very low sand concentrations.
Acceptable production was in the 750 mscfd to
1 mmscfd (2.1 to 2.8 E4m3/d) range.
The solution is to run the StimGun assembly in 3500 psi (24 MPa), and then nitrogen pressure is
a tubing-conveyed perforating (TCP) gun configu- used to create the EOB condition with 11,500 psi
ration and apply extreme overbalance pressure. (79 MPa) of surface pressure typical. This translates
Propellant coverage is typically 40 to 50% of the to ~15,000 psi (103 MPa) bottom hole treating
net pay perforated. TCP guns are generally run pressure. Upon detonation, nitrogen is used to dis-
under a 10,000 psi (69 MPa) packer with an on- place the treatment at a rate of 8000 scf/min. for
off tool and tubing to surface. Job design also uses five minutes, then nitrified 20% acid is pumped
300 ft (91 m) of 20% acid as the incompressible ~1000 gals (4 m3) of acid at 5000 scf/min
spearhead. The annulus is usually pressured up to (142 m3/min), depending upon treating pressure.
Upon completion of the nitrified acid
injection, flow back is initiated imme-
10
diately with a full open choke for
9 one to two tubing volumes.
8
Producing rate mmscfd

The wells respond splendidly. The

7 first well completed flowed at a rate
of 3 to 3.5 mmscfd (8.5 to
6
9.9 E4m3/d). Subsequent wells pro-
5 duce in the range of 3 to
4 10 mmscfd (8.5 to 2.8 E5m3/d).
3 Considerable rig time is saved
because wells are producing within
2
hours of the treatment. This has
1 now become a best practice solu-
0 tion to completing these wells.
Before StimGun After StimGun

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An overview of SPE paper 68101:

A unique approach to enhancing
production from depleted, highly
laminated sand reservoirs using
a combined propellant/perforating
technique
Kim Hungerford, Halliburton Energy Services

I ndustry has had great success in removing near-

wellbore damage caused by perforating wells in an
underbalanced condition. However, if the formation
In Egypt, an operator was not obtaining the desired
flow efficiency from conventional, tubing-conveyed,
underbalanced perforating methods. Given the low
pressure is too low, this technique is not always suc- formation pressure, it was probable that during perfo-
cessful. By using the combined stimulation and per- rating, the differential pressure created was insufficient
forating technique (StimGun assembly), the near- to remove the induced perforating damage. To
wellbore damage in depleted reservoirs can be suc- improve the effective conductivity from the reservoir,
cessfully removed. Halliburton presented some of the StimGun assembly combination stimulation/per-
their results in the SPE Paper 68101: A Unique foration technology was used to enhance the under-
Approach to Enhancing Production from Depleted,
balanced perforating. This successfully reduced the
Highly Laminated Sand Reservoirs Using a Combined
skin and increased the flow efficiency.
Propellant/Perforating Technique, written by H. El-
Bermawy, SPE, Agiba Petroleum Company and H. El- The reader is encouraged to review the paper in its
Assal, Halliburton Energy Services. This paper was entirety. The detailed discussion of the problem, the
presented at the 2001 SPE Middle East Oil Show held possible solution, the results, and of operational pre-
in Bahrain, 17-20 March 2001. This entire paper, cautions is extremely informative and applicable
with due recognition to the SPE for allowing its given the increased interest in stimulation of low
republication, is included in Appendix. pressure reservoirs.

Case 1
Conventional underbalanced perforating
Skin: +23
Flow Eff.: 0.27

Case 2
StimGun underbalanced perforating
Skin: -4
Flow Eff.: 1.19

Case 3
StimGun underbalanced perforating
Skin -2
Flow Eff. 1.25

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

Successfully combining the StimGun

assembly with Pow*rPerf
technologies
Frank Oriold, Canadian Completion Services The Expro Group

C anadian Hunter, now Devon Energy, operates

the Ring Border gas field which straddles the
Alberta/British Columbia border. In some cases the
3000 ft (900 m). The maximum pressure that can be
safely applied to the wells is around 6700 psi
(47 MPa). It appears that this combination of shallow
wells contain two producing horizons, the Bluesky wells and small tubing combine to reduce the effec-
and Monteny formations. The Bluesky, when pres- tiveness of the Pow*rPerf process.
ent, requires stimulation to be productive. Typical In an attempt to improve completion methods, it
treatments such as four or five tonne
batch fracs tend to be risky due to
Tubing with high pressure nitrogen
the close proximity to water. As a result
of these issues, the Pow*rPerf comple- Radioactive marker sub
tion technique was used to overcome Tubing joint
skin damage.
Pow*rPerf is a Marathon Oil
Company patented process that com-
bines extreme overbalance (EOB) per- Retrievable 10K packer
forating with a specially modified gun
body that contains 20/40 mesh baux-
ite. Special shaped charges open the
bauxite carrier, ejecting the material
into the fluid/expanding gas stream
10 ft (3.1 m) pup joint
during the extreme overbalance job.
The erosive attributes of the bauxite
coupled with the high pressure and X profile
velocity of the expanding gas and fluid
stream make this a very effective tool
in the treatment of near-wellbore dam- 10 ft (3.1 m) pup joint
age in the perforations. Canadian
Jar up mechanical tubing release
Hunter had performed transient analy-
sis on some of the wells and discovered
than skin was not completely removed
utilizing this technique alone in some 10 ft (3.1 m) pup joint
Auto venting pressure activated firing head
of the Bluesky wells.
Solution
Use of high-speed pressure gauges
Gun with proppant
have also shown that pressure loss due to
friction can be significant in extreme
overbalance operations. This is especially 238 in. (60.3 mm) 6 spf (20 spm) 60 phase perforating gun with 75%
true in wells that use small tubing. In the coverage of 3.5 in. (89 mm) OD StimGun sleeve
Ring Border gas field, the production
tubing is 2 38 in. (60.3 mm) OD and the
wells are shallow at approximately
Typical StimGun/Pow*rPerf TCP assembly.

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was thought that combining the StimGun assembly Results

with Pow*rPerf might increase the effectiveness of the To date, more than 30 of these combination jobs
treatments, and it been a great success. The initial ener- have been performed in the area. It appears that the
gy provided by the StimGun assembly was used in StimGun does indeed assist in reducing total skin
these completions to break down near-wellbore dam- because production numbers are up from these wells
age and initiate a small fracture. Because the StimGun by approximately 25%. The breakdown/leak-off profile
assembly and the associated high energy gas pulse act of nitrogen into the formation is now significantly dif-
to break down all the perforations, it is thought that the ferent and seems to indicate that a more efficient path
Pow*rPerf portion of the job is more effective because to the formation has been created.
the stored energy in the tubing would be needed only
As a result of these successes, more than 80% of the
for fracture extension as opposed to perforation break-
extreme overbalance jobs performed by The Expro
down. By combining the two technologies, the issue of
Group in Canada now incorporate StimGun assembly
friction loss should be of lesser consequence.
as a perforation breakdown tool.

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

Slickline-conveyed StimTube tool

stimulation: an alternative to
high-rate acid fracture
Bill Barton, Tripoint, Inc. The Expro Group

I n May 2001, ExxonMobil contracted Tripoint to

perform a StimTube tool stimulation on slick-
line for a well candidate on the Hondo Platform,
(3855 to 3863 m) with 15 ft (4.6 m) of StimTube
tool on each run. The well was then returned to
production. Before and after producing rates are as
offshore California. The well chosen was produc- follows:
ing from the Vaqueros formation. The H-36 ST Before: 356 BOPD (57 m3)
well had been damaged during its initial comple-
After: 890 BOPD (141 m3)
tion, and current production was lower than cal-
culated reservoir performance. The H-36 ST oil Stabilized Rate: 800 BOPD after 6 weeks
producer would require a high-rate, acid fracture (127 m3)
stimulation to improve production at an estimat- Clearly, the work was very successful. ExxonMobil
ed cost of $500,000. Other issues involved in per- subsequently planned and executed further
forming the fracture stimulation on this well workovers using this technology as well as the
involved strict offshore environmental regulations StimGun assembly combined with tubing-con-
concerning this type of work and a lack of rig veyed underbalanced perforating for new well com-
space available to perform the fracture stimula- pletions in the field. As a result of this successful
tion that the well required. procedure, four more wells were treated with
ExxonMobil decided to use the StimTube tool as StimTube tools in this field. In three of the four
a near-wellbore stimulation method as an alterna- cases production increased over original numbers.
tive to the fracture stimulation. PulsFrac modeling Accurate production numbers were not available
suggested fractures could be created 2 to 3 ft because of the limited amount of gas available for
(.6 to 1 m) from the wellbore, and the operator felt lifting operations on the platform. The operator
this was sufficient to reach past the near-wellbore stated, however, that the platform was delivering
damage as well as break down plugged perfora- more than 10,000 barrels of oil per day (bopd) for
tions. The StimTube the first time in five years.
tool would eliminate
environmental impact The StimTube tool eliminated
risk, reduce production
down time, and at the
environmental impact risk, reduced
same time be more cost production down time, and at the same
effective. The desired
result was additional per-
time was found to be more cost effective.
foration breakdown and
the initiation of a fracture near the wellbore. This This is one of many examples showing removal
job was designed to be conveyed on slickline, of near-wellbore damage via the use of the propel-
which was also one of the first such applications for lant technology. In the US, the propellant technol-
the technology. A slickline gamma ray correlation ogy has been most effective as a near-wellbore
memory tool was deployed first to establish positive stimulation in formations where fractured reser-
depth control for the subsequent operations. The voirs damage, and fracture plugging exists.
StimTube tool was then deployed utilizing a mem- Internationally, use of the technology for near-
ory tool slickline firing system. Two separate runs wellbore stimulation has been successful where
were conducted to intervals 12,674 to 12,689 ft higher permeability reservoirs are damaged by
(3863 to 3868 m) and 12,649 to 12,674 ft non-optimal drilling or completion practice.

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Propellants have dramatically

increased production from heavy oil
wells: the need for hydraulic fracturing
has been reduced
Kevin Newmiller, Precision Drilling
Perry M. Huber, Plains Perforating Ltd.

I n order to effectively obtain production

from heavy oil sands in
Canada, either a
hydraulic fracture or the
creation of sand produc-
tion (along with the oil), or
both, have been required.
Propellant tools have greatly
reduced the need for hydraulic
fracturing; and have greatly
increased sand/oil production in
areas where this is necessary.
Bakken formation replacing hydraulic
fracturing
The Bakken formation is an unconsolidated sand-
stone within the Mannville group of sands. Located Heavy oil areas in Western Canada.
in Western Saskatchewan, the zone contains
14 to 19 API gravity oil. The average porosity is
High-speed pressure gauges and computer models
30% and the average perforation interval is 11.6 ft
using the PulsFrac software are run in conjunction
(3.5 m). Traditionally, wells have been stimulated
with each propellant stimulation to monitor results
through the use of 32,500 lbs (15 tonne) sand fracs
and to aid in refining the amount of propellant
at an average cost $25,000 per fracture.
required to obtain satisfactory results. As a result of
As of this writing, over 100 wells have been pro- this optimization, perforation shot density has been
pellant stimulated in this field. The operator has increased to 6 spf (20 spm) from 5 spf (17 spm), and
indicated that wells with an average porosity equal the propellant coverage has been increased to an
to or greater than 30% do not require a hydraulic average of 80% from an initial average of 60%. This
fracture stimulation following the propellant stimu- has resulted in a more complete propellant burn
lation. In total, 58% of the wells fall into this cate- with improved burn pressures and fracture lengths.
gory. The remaining wells required hydraulic frac-
The use of StimGun has reduced the need for
turing but less pressure was needed to initiate the
hydraulic fracturing in the Bakken formation by 58%.
fracture stimulation.

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

Bakken Examples

Case 1
Bakken formation: 34% porosity

5.6 ft (1.7 m) perforation interval with 3.9 ft (1.20 m) propellant sleeve

Maximum burn pressure: 3900 psi (27 MPa)

Fracture extension: 7.5 ft (2.3 m)

Results: Successful stimulation no fracture treatment required.

55

50 Penn West Hoosier

111/13-23-031-27 W3/00
45 Bakken 833 m
86 mm, 24 gm, 17 spm, 60 x 1.7 m
40 High-speed pressure data

35
Pressure - MPa

30

25

20

15

10

0
0.000 0.003 0.006 0.009 0.012 0.015 0.018 0.021 0.024
Time - seconds

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Case 2

Bakken formation: 33% porosity

6.6 ft (2.0 m) perf interval with 4.9 ft (1.5 m) propellant sleeve

Maximum burn pressure: 4930 psi (34 MPa)

Fracture extension: 7.5 ft (2.3 m)

Results: Successful stimulation no fracture treatment required. Increase in shot density improved
burn pressure.

45

40 Penn West Hoosier

131/05-06-031-26 w3/00
Bakken 871 m
35 86 mm, 26 gm BH, 20 spm, 60 x 2.0 m
High-speed pressure data
30
Pressure - MPa

25

20

15

10

0
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050
Time - seconds

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Case 3
Bakken formation: 25% porosity

9.8 ft (3.0 m) perf interval with 8.9 ft (2.7 m) propellant sleeve

Maximum burn pressure: 9100 psi (63 MPa)

Fracture extension: 8.4 ft (2.55 m)

Results: Successful stimulation well had a slight blow on the casing following stimulation
despite the reduced formation porosity in this example. Increased coverage yielded
higher burn pressure and resulted in a complete propellant burn.

65
60 perf gun
55 l

50
45
Pressure - MPa

40 Penn West Milton B14

121/14-16-30-28 W3/00
35 Bakken
30 86mm, 24 gm, 17 spm, 60 deg
High-speed pressure data
25
20
15
10
5
0
0.000 0.005 0.010 0.015 0.020 0.025 0.030
Time seconds

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Case 4

Bakken formation: 33% porosity

17.8 ft (5.4 m) perf interval with 14.8 ft (4.5 m) propellant sleeve

Maximum burn pressure: 8400 psi (58 MPa)

Fracture extension: 10.3 ft (3.13 m)

Results: Successful stimulation no hydraulic fracture required. Optimized shot density and propel-
lant coverage resulted in improved fracture extension.

60
55
50
45 perf gun
l
40
Pressure - MPa

Penn West Loverna

35 141/04-24-031-28 w3/00
30 Bakken 845 m
86 mm, 26 gm BH .8, 20 spm, 60 x 5.4 m
25 High-speed pressure data
20 -- propellant ignition
15
10
5
0
0.00 0.01 0.02 0.03 0.04 0.05
Time - seconds

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

Enhancing sand/oil production

in the Lloydminster Canada area
David Cuthill, Computalog Wireline Services
Lane Merta, Computalog Wireline Services

I n Lloydminster, Canada, to achieve oil production

from the majority of unconsolidated heavy oil
wells, both the sand and oil must pumped to sur-
face. The sand is separated from the oil at surface
and discarded (Figure 1). All too frequently, the
production in these wells unexplainably declines.
This is normally attributed to a lack of sand mobili-
ty or the bridging of the sand grains. Propellant
technology using the WST has been very success-
fully used to disrupt the presumed sand bridges
and re-establish economic production rates.
Figure 1 Sand and oil are pumped to surface and the
The procedure is to pull all pumps, rods, and oil is separated from the sand. The sand is subsequently
tubing from the well. If the well bottom is within discarded and stockpiled.
6.56 ft (2 m) of the stimulation interval, any fill
must be removed. The WST propellant has a pressure as possible or propellant burn velocity
unique ignition system and can be successfully will rapidly decrease to zero. To maintain back
ignited and combusted under shallow, high per- pressure it is necessary to have as much fluid
meability conditions. After initiation the propel- (produced fluid, blended with lighter oil or KCI
lant burn must be contained by as much back water) in the wellbore as possible. In some cases

70

60 Propellant ignition,
rapid pressure leak-off,
and prolonged
50 burn normally
observed due to lack
of confinement.
Pressure - mPa

40

30

20

10

0
0 0.005 0.01 0.015 0.02 0.025
Time - seconds
Figure 2 Typical pressure vs. time high-speed gauge data from WST heavy oil applications in the Lloydminster area.

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where the formation will not support a fluid column, coiled tubing may be required until the sand cut,
packers can be set and then released after the well- declines to a manageable level where common
bore is full and the propellant tool is positioned and pumping methods can be used.
ready to fire. Alternatively, fluid can be pumped When the high-speed pressure gauge is used, a
before and during the stimulation. Several successful graphical presentation of the stimulation event can be
stimulations have been carried out while pumping generated for analysis with the help of the PulsFrac
with pressure on the wellhead. Generally, under software. It is sometimes difficult to get a complete
these conditions, any method that will provide a propellant burn in this application so the pressure
fluid column with as much back-pressure as possible, pulse is viewed to determine the burn efficiency.
will enhance tool burn efficiency and the effective- Propellant ignition followed by a rapid pressure
ness of the stimulation. After the stimulation, produc- decline is indicative of the observed response in this
tion should be resumed as soon as practical. Due to shallow unconsolidated environment, as shown in
increased sand cut a sand pump or foaming with Figure 2.

Case 1
Objective: Well had been shut in for a period of three years due to low productivity

Solution: A propellant WST was proposed as a method of reinitiating economic production

Configuration:
Orientation: Vertical
Formation: Basal Mannville sandstone; 2165 ft (660 m)
Casing size: 7 in. (177.8 mm)
Tool: 2.5 in. (63.5 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil

Results: Added 63 bbls (10 m3) of fluid prior to propellant ignition to maintain sufficient tamp column height.
After stimulation production sustained at 44 bpd (7 m3/d), oil.

Case 2

Objective: Well was suspended due to low productivity

Solution: A propellant WST was proposed as a method of reinitiating economic production

Configuration:
Orientation: Vertical
Formation: Rex sandstone; 1935 ft (590 m)
Casing size: 7 in. (177.8 mm)
Tool: 2.5 in. (63.5 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil blend
Results. After stimulation sand inflow increased significantly. Production sustained at 60 bpd (9.5 m3/d), oil.

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Case 3
Objective: Well was producing at an uneconomic rate of 6 bpd (1 m3/d), oil

Solution: A propellant WST was proposed as a method of increasing production rate

Configuration:
Orientation: Vertical
Formation: Sparky sandstone; 1739 ft (530 m)
Casing size: 7 in. (177.8 mm)
Tool: 2.5 in. (63.5 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil blend

Results: After propellant stimulation production increased to a sustained rate of 38 bpd (6 m3/d), oil.

Case 4
Objective: Horizontal heavy oil well, completed with a slotted liner, producing at 19 bpd (3 m3/d) with a 35%
water cut. Propellant was suggested as a method of increasing productivity

Solution: A propellant WST was proposed as a method of clearing the liner slots and stimulating the forma-
tion behind the liner

Configuration:
Orientation: Horizontal
Formation: McLaren sandstone; 6100 ft (1850 m)
Casing size: 7 in. (177.8 mm) slotted liner
Tool: 2 in. (50.8 mm) WST, conveyed on tubing with high-speed gauge
Tamp: Produced water

Results: After stimulation well producing at 82 bpd (13 m3/d) at a 35% water cut. Liner was not damaged
during stimulation treatment.

Case 5
Objective: New well completion on perforating no measurable inflow

Solution: A WST was proposed as a method of initiating production

Configuration:
Orientation: Deviated
Formation: Cummings sandstone; 1755 ft (535 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, propellant conveyed on wireline with high-speed gauge
Tamp: Oil

Results: Pumped 63 bbls (10 m3) of tamp fluid prior to propellant ignition. After stimulation well producing
at 82 bpd (13 m3/d), oil.

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Case 6

Objective: Well was producing at an uneconomic rate of 22 bpd (3.5 m3/d), oil

Solution: A WST was suggested as a method of stimulating increased production

Configuration:
Orientation: Vertical
Formation: Colony sandstone; 1854 ft (565 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil

Results: After propellant stimulation production increased to and stabilized at 53 bpd (8.5 m3/d), oil.

Case 7
Objective: Well was suspended due to low productivity

Solution: A WST was proposed as a method of reinitiating production

Configuration:
Orientation: Vertical
Formation: Basal Mannville sandstone; 1657 ft (505 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Produced oil

Results: After propellant stimulation the well began producing at 38 bpd (6 m3/d), oil.

Case 8
Objective: Well was suspended due to low productivity

Solution: A WST was proposed as a method of reinitiating production

Configuration:
Orientation: Vertical
Formation: Basal Mannville sandstone; 2050 ft (625 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil

Results: After the propellant stimulation production increased to 31 to 44 bpd (5 to 7 m3/d), oil.

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Case 9

Objective: Well was producing at 6 bpd (1 m3/d), oil

Solution: A WST was proposed as a method of increasing production

Configuration:
Orientation: Vertical
Formation: General petroleum sandstone; 1460 ft (445 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil

Results: After the propellant stimulation production increased to 38 to 44 bpd (6 to 7 m3/d), oil.

Case 10
Objective: Well was producing at unacceptable rates

Solution: A WST in combination with a solvent soak/squeeze was proposed as a method of reinitiating pro-
duction

Configuration:
Orientation: Vertical
Formation: Waseca sandstone; 1115 ft (340 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Xylene & oil blend
Results: After the propellant stimulation production increased to 25 bpd (4 m3/d), oil.

Case 11
Objective: Well was suspended due to low productivity
Solution: A WST was proposed as a method of reinitiating production

Configuration:
Orientation: Deviated
Formation: Upper Waseca sandstone; 1476 ft (450 m)
Casing size: 7 in. (177.8 mm)
Tool: 2 in. (50.8 mm) WST, conveyed on wireline with high-speed gauge
Tamp: Oil
Results: After the propellant stimulation no sustainable production was possible due to an extremely high
sand cut. A foam cleanup was used to remove sand and debris. Production increased to economic
rates.

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Stimulation of shallow gas wells

David Cuthill, Computalog Wireline Services

S uccessfully completing shallow gas wells can be a

challenge especially in intervals that are near
water. In many instances perforating alone will not
method of clearing the formation and perforations.
The focused nature of the stimulation means that it
can be used in applications where more aggressive
provide sufficient inflow performance. Low reservoir stimulations may result in the increase of undesirable
pressure does not generally provide adequate differ- near-water production.
ential pressure and inflow velocities to flush the near-
Mechanism
wellbore region. Remedial efforts such as modest
skin fracs, for near-wellbore stimulation, run the The stimulation mechanism for a StimGun treatment
risk of connecting to water. is identical to the stand-alone propellant tools with the
unique difference that the propellant event takes place
The StimGun assembly has been demonstrated to at the time of perforating. Once positioned on depth,
provide sufficient stimulation energy to clean up the detonating the shaped charge contained within the
near-wellbore region while remaining in the zone. perforating carrier ignites the propellant sleeve. As the
Shallow gas wells stimulated using this advanced per- propellant burns, a surge of high-pressure gas is pro-
forating technique have performed to potential with- duced that enters the newly created perforation path,
out the need for additional costly and sometimes breaking through the damage around the perforation
unpredictable stimulations. When dealing with near- tunnel. For underbalanced stimulations, an increased
wellbore production restrictions, propellant stimula- back-flushing effect has been demonstrated to further
tion devices can be an inexpensive and effective enhance the stimulation.
Propellant devices require confining pressure in order
to promote an efficient burn. Confining pressure is
obtained by placing a fluid column of sufficient height
over the propellant tool > 650 ft (>200 m) for the
Nitrogen StimGun assembly. Twice the minimum amount is
ideal. In shallow wells adequate fluid height sometimes
cannot be obtained due to the depth of the well. In
addition, placing excessive fluid over the interval is
undesirable due to the low reservoir pressure and con-
cern over fluid injection into the formation following
perforation. An efficient propellant burn can be
obtained by placing a minimal amount of a formation
compatible fluid over the interval and applying ade-
Compatible liquid quate nitrogen pressure at the surface over that fluid
column (see Figure 1). Effective confinement is
obtained and the StimGun assembly can be ignited.
After initiating the StimGun assembly, the nitrogen
Perforating carrier pressure is immediately released to minimize fluid injec-
tion and allow back-flushing of the formation.
Propellant sleeve
Pressure data
Sleeve retainer ring When a high-speed pressure gauge is used, a
graphical presentation of the stimulation event can
be generated for analysis. The analysis can be used to
Figure 1 - Wellbore schematic illustrating how nitrogen determine the effect of the stimulation on the forma-
pressure has been utilized to increase propellant confining tion and to evaluate the burn of the propellant. The
pressure. configuration and job execution for this application

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A p p l i c a t i o n Ty p e : N e a r- W e l l b o r e S t i m u l a t i o n

15

Tool
10
ignition
Pressure - MPa

5
Bleed off
nitrogen
Pressurize with
nitrogen from
On depth
surface
Run In POOH
hole
0
0 25 50 75
Time - minutes

Figure 2 - Example pressure plot illustrating well pressurization and post stimulation pressure bleed-off to minimize fluid
injection.

Case histories

Case 1
Objective: The interval has near water. Hydraulic fracturing brings in water production and standard perforat-
ing does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1132 ft (345 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm)
& 60 phasing conveyed on wireline
Tamp: KCl with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at an acceptable rate of
225 mcf/d (6.4 E3m3/d), gas, with no observed water production. Hydraulic fracturing was avoided.

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Case 2
Objective: The completion interval has near water. Previous fracing attempts in the field have brought in water pro-
duction, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1181 ft (360 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm) &
60 phasing conveyed on wireline
Tamp: Water/methanol with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 300 mcf/d (8.5 E3m3/d), gas, with a
WGR of 8.4 bbl/mmcf (3.8 m3/100 E3m3). Hydraulic fracturing was avoided production at acceptable
rate.

Case 3
Objective: The completion interval has near water. Previous fracing attempts in the field have brought in water pro-
duction, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1335 ft (407 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm) & 60
phasing conveyed on wireline
Tamp: Water/methanol with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 5.9 E3m3/d (210 mcf/d), gas, with
a WGR of 24.9 bbl/mmcf (11.3 m3/100 E3m3). Hydraulic fracturing was avoided production at accept-
able rate.

Case 4
Objective: The completion interval has near water. Previous fracing attempts in the field have brought in water pro-
duction, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1335 ft (406 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm) & 60
phasing conveyed on wireline.
Tamp: Water/methanol with 1000 psi (6.9 MPa) nitrogen over pressure.

Results: After completion with StimGun assembly, the well was producing at 153 mcf/d (4.3 E3m3/d), gas, with
a WGR of 6.7 bbl/mmcf (3.0 m3/100 E3m3). Hydraulic fracture was avoided production at acceptable
rate.

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Case 5
Objective: The completion interval has near water. Previous fracing attempts in the field have brought in
water production, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1345 ft (410 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm)
& 60 phasing conveyed on wireline
Tamp: Water/Methanol with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 127 mcf/d (3.6 E3m3/d), gas,
with no observable water production. Hydraulic fracturing was avoided production at acceptable
rate.

Case 6
Objective: The completion interval has near water. Previous fracing attempts in the field have brought in
water production, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1207 ft (368 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm)
& 60 phasing conveyed on wireline
Tamp: Water/Methanol with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 92 mcf/d (2.6 E3m3/d), gas,
with no observable water production. Hydraulic fracturing was avoided production at acceptable
rate.

Case 7
Objective: The completion interval has near water. Previous fracing attempts in this field have brought in
water production, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1843 ft (257 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm)
& 60 phasing conveyed on wireline
Tamp: Water/Methanol with 1000 psi (6.9 MPa) Nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 107 mcfd (3.0 E3m3/d), gas,
with no observable water production. Hydraulic fracturing was avoided production at acceptable
rate.

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Case 8
Objective: The completion interval has near water. Previous fracing attempts in this field have brought in water
production, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1119 ft (341 m)
Casing size: 412 in. (114.3 mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm) &
60 phasing conveyed on wireline
Tamp: Water/methanol with 1000 psi (6.9 MPa) nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 236 mcf/d (6.7 E3m3/d), gas, with
a WGR of 2.6 bbl/mmcf (1.2 m3/100 E3m3). Hydraulic fracturing was avoided production at acceptable
rate.

Case 9
Objective: The completion interval has near water. Previous fracing attempts in this field have brought in water pro-
duction, and standard perforating does not provide maximum expected inflow.

Solution: A StimGun assembly was run to initiate localized near-wellbore clean up.

Configuration:
Orientation: Vertical
Formation: Bluesky sandstone; 1171 ft (357 m)
Casing size: 412 in. (114.3mm)
Tool: 3.375 in. (85.7 mm) StimGun assembly over 2.75 in. (70 mm) ERHSC loaded at 6 spf (20 spm) &
60 phasing conveyed on wireline
Tamp: Water/methanol with 1000 psi (6.9 MPa) nitrogen over pressure

Results: After completion with StimGun assembly, the well was producing at 206 mcf/d (5.8 E3m3/d), gas, with
a WGR of 11.69 bbl/mmcf (5.3 m3/100 E3/m3). Hydraulic fracturing was avoided production at accept-
able rate.

makes the pressure recording an important tool to low reservoir pressure does not clean up the near-
determine if the propellant burned correctly. wellbore region.

Conclusions Remedial efforts such as modest skin fracs run

the risk of connecting to water.
Applications have demonstrated that the StimGun
assembly can be an effective method of stimulating The StimGun assembly has been demonstrated
shallow wells. to provide sufficient stimulation energy to clean
up the near-wellbore region while remaining in
In many instances perforating alone will not
zone.
provide sufficient inflow performance because the

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Application Type: Open Hole Stimulations

Open hole completions: case

histories and technical studies with
formation micro imaging (FMI)
Brent Kirschner, Owen Oil Tools

H istorically, propellants were used mostly in

open holes. There continues to be interest in
the StimGun assembly and other related tech-
was indicated. Formation stimulated varied
from sands to shales to carbonates at well
depths no greater than 3500 ft (1067 m). Of
nologies in open hole applications to overcome special significance is that FMI fracture identifi-
near-wellbore damage and as a pre-treatment to cation logs were run both before and after the
enhance additional stimulations. These products propellant jobs. The logs clearly show fairly
initiate and propagate fractures over very long intense multiple fracturing in the stimulated
intervals (considerably longer than the interval interval and then bi-winged fracturing up to
stimulated). A number of open hole wells have 100 ft (30.5 m) upwards and downwards away
been successfully treated using this approach, pri- from the tool. Calculations (Figure 3) show that
marily using the Well Stimulation Tool (WST). This open hole fractures at the tool can extend deeply
fracturing mechanism has been documented by into the formation. Away from the tool, although
formation micro imaging (FMI) and video logs, fractures are created, they are much less deep.
and is discussed below. This is because fractures are gas/liquid-driven
From an operational standpoint open hole stim- near to the tool and only liquid driven away from
ulations with propellants require the tool.
some additional planning. One
early concern is the possibility no known open hole collapses
of open hole collapse due to have been associated with the use of
the high-pressure gas surge.
Over a many year period, no StimGun products, even though
known open-hole collapses they have been used in a variety of
have been associated with the
use of StimGun products, even
formation types
though they have been used in
a variety of formation types. Nevertheless, care An operator in the Odessa, Texas area
must be taken not to overpressure holes; anecdot- stimulated one of the first open hole horizontal
al evidence obtained from others indicates that wells where a long interval was treated with
hole collapse is not impossible. the WST. The well was in the San Andres
The Well Stimulation Tool (WST), a cylindrical, Dolomite formation (2 md permeability
solid configuration, is most commonly run in open- estimate, 4500 ft (1372 m) TVD, 8 in.
hole applications. The WST is conveyed inside a (203 mm) open hole.) Two runs were made,
vented carrier to protect the tool and to allow the one 200 ft (61 m) in length and the other
combustion gases to readily escape to the wellbore. 880 ft (268 m) in length, both with 3 in.
(76.2 mm) diameter WST. Subsequent to the
Case histories stimulations, there was no additional tool drag
The following case histories have been selected after either run; although there were large
for review: increases in incremental production, it was
mostly water. The operator acidized the well
In Oklahoma, the Propellant Technology
one year later. The hole was still open and acid
Development Group made six runs with 6 ft
injection pressures indicated the fractures from
(1.8 m) and 12 ft (3.6 m) WSTs in an open
the propellant stimulation were still effective.
hole filled with drilling mud. No hole collapse

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Formation micro logs of a Oklahoma test well showing fracture length profile where FMI
logs were run before and after shooting propellant

Before propellant After propellant

A. 6 ft x 2 in. WST Tool was shot at

A 2472 - 2478 ft in a limey shale sec-
tion. Please note the created fractures
on the After propellant logs that
extend vertically up and down the
open hole wellbore.

B. A 6 ft x 2 in. WST tool was shot at

B 2514 - 2520 ft in a limestone formation.

Figure 1 FMI Log 1

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Application Type: Open Hole Stimulations

Before propellant After propellant

C. Two WST tools (one 6 ft and one

C 12 ft) were shot at 2954 - 2960 ft
and 2950 - 2962 ft respectively in
this shale formation.

Figure 2 FMI Log 2

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the model; the data gave strong

2100 indications (later substantiated by the
operators) that the toe of the well, where
the 80 ft (24 m) of propellant was
ignited, was out of zone and in a carbon-
ate formation. Both the pre-and post-job
modeling are available, as well as the fast
2300 pressure gauge data from the job. No
production results are available, as this
job was primarily a test case in soft
sandstones before conducting a planned
Depth in Well, ft

North Sea application.

A Canadian operator stimulated the
2500
Halfway Sand in a British Columbia
horizontal well (15 md permeability,
8200 ft (2500 m) TVD, 6 in. (152.4 mm)
open hole). Two 7 ft (177.8 mm) runs
with 2 in. (50.8 mm) diameter WST were
used to successfully initiate fractures for
2700
subsequent stimulation. This was a pre-
frac application and was successful. No
open hole collapse was noted in this
higher stress environment at increased
depth.
2900 In North Dakota, an operator stimu-
0 5 10 15 20 lated a Bakken 2000 ft TVD horizontal
Fracture Length, ft well with 500 ft (152.4 mm) of 2.5 in.
Figure 3 Typical calculated maximum fracture length profile near and (63.5 mm) diameter WST. This was a
away from tool (2 in. (50.8 mm) diameter by 12 ft long WST at 2500 ft in high bottom hole temperature
8 in. open hole). At tool 6 fractures. Away from tool 2 fractures. application. The tools sat on bottom
overnight and the WST was successful
An operator in western Canada stimulated the ignited. Production increased from
Alida Beds (1 md carbonate at 4200 ft 30 bfpd (4.8 m3/d) to greater than 300 bfpd
(1280 m) TVD, 6 in. (152.4 mm) hole) with (48 m3/d), but due to mechanical problems not
160 ft (49 m) of 2.5 in. (63.5 mm) WST, and the related to the stimulation the well was killed by
stimulation assembly was pulled with minimal to pumping water. The equipment was retrieved
no drag. Incremental oil production was approxi- without any indications of hole collapse.
mately 100 bopd (16 m /d), which decreased to
3 Production was re-established at 70 bfpd
an incremental 25 bopd (4 m3/d) during the (11.2 m3/d) and increased to 120 bfpd (19 m3/d)
before slowly declining to 60 bfpd (9.5 m3/d) one
following one year period.
year later.
An operator in the Hobbs, New Mexico area
A Canadian operator stimulated an Alberta open
stimulated the Delaware sand, which is soft and
hole Leduc D3 Dolomitic limestone well in three
loosely consolidated (50 md to 100 md, 6 in.
wireline runs with 2.5 in. (63.5 mm) diameter
(152.4 mm) open hole) with 2 in. (50.8 mm) and
13 ft (4 m) WST. This well is at 8200 ft (2500 m),
2.5 in. (63.5 mm) WST in 80 ft (24 m) and 220 ft
had 50 md to 150 md permeability and a 6 in.
(67 m) runs, respectively. There were no
(152.4 mm) open hole. After all three runs, no fill
problems getting in or out of the hole on either
was tagged on bottom, and the operator
run. The more interesting facet of this job was subsequently pumped a small acid job after the
that it was the first horizontal well in which the propellant breakdown/stimulation. Production
downhole pressure gauges were used to verify

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Application Type: Open Hole Stimulations

went from 200 bopd (32 m3/d) and In Australia, an operator successfully stimulated
4800 bwpd (763 m3/d) to 800 bopd a coalbed methane extraction well (650 ft
(127 m3/d) and 4200 bwpd (668 m3/d). After (198 mm), 5.0 in. (127 mm) hole, .4 md
one year, production was 600 bopd (16 m3/d), permeability). The well was stimulated in five
4400 bwpd (700 m3/d). After three years, the runs with 2.0 in. (50.8 mm) and 2.5 in.
well was still producing 400 bopd (64 m3/d) (63.5 mm) diameter WST. There was some tool
and 4600 bwpd (731 m3/d). High-speed drag after the first run, but after successfully
pressure data are available from all three runs. making all five runs, the operator had to

Figure 4 Video log frame from section at tool showing 6 fractures (contrast-
enhanced).

Figure 5 Video log frame from section away from tool showing 2 fractures (contrast-
enhanced).

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circulate out only some coal fines from the well. not be broken down prior to the propellant
The well was successfully taking fluid and then stimulation, acid was subsequently utilized there-
producing gas, but the other information from after. High-speed pressure data for three of the
the well was held confidential. Fast pressure four propellant runs is available.
gauge data from the WST stimulations and model In Texas, an operator shot 10 ft (3 m) of 2.0 in.
data are available. (50.8 mm) diameter WST to restore production
An operator in Wyoming made eight runs with after a cross-link polymer job. This job was
propellant in open hole Dolomite formations with successful in restoring production in this 10 md
no hole collapse problems. These eight runs were Grayberg dolomite open hole producer (2600 ft
on wireline with 2.0 in. (50.8 mm), 2.5 in. (792.5 m) TVD, 7.5 in. (190.5 mm) open hole).
(63.5 mm), and 3.0 in. (76.2 mm) diameter WST In Michigan, an operator ran three 12 ft
tools. Some increases in injection rates were
(3.6 m) WST jobs in open hole sections of
noticed and pressure data is available from this
sandstone at about 1500 ft (457.2 m) in an
4700 ft (1433 m) well.
attempt to restore deliverability to gas storage
The same Wyoming operator as listed above wells. Video logs were run subsequent to the jobs.
stimulated a 3200 ft (975 m) deep Wyoming No hole collapse occurred and the observed
dolomite formation with tubing conveyed fracture patterns were similar to the ones
systems consisting of 1.5 in. (38.1 mm), 2.0 in. described in the first case study above. That is,
(50.8 mm) and 2.5 in. (63.5 mm) diameter WST. there were four to six fractures near the tool and
No open hole collapse was noted and some long, running bi-winged fractures away from the
increases in well injectivity were noted. tool as shown in Figures 4 and 5. The WSTs were
A Canadian operator stimulated a northern run in water, and the water injected to the forma-
Alberta Belloy Sandstone open hole well to estab- tion probably created water blockage problems,
lish injectivity (5 md, 7900 ft (2407.9 m) TVD, so the jobs did not improve the gas deliverability
(83 mm) open hole). There were no hole collapse of these wells. Reservoir pressure was not high
issues in four wireline runs of 2.5 in. (63.5 mm) enough to generate significant clean-up. Presently
and 3.0 in. (76.2 mm) diameter WST covering strongly recommend the use of non-damaging
52 ft (15.8 m) overall. Although the well could fluids when stimulating injection wells.

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G e n e r a l I n t e r e s t a n d W h a t s N e x t

Myths and misconceptions

John Schatz, John F. Schatz Research & Consulting, Inc.

I have wanted to write this article for years, but

never have had a suitable venue, or perhaps the
nerve. This booklet finally provides that venue. My
friends and colleagues have provided the nerve.
What I write here is neither pure science nor pure
marketing, but a collection of observations made
over a period of twenty-five years.
Treating wells with propellants, whether along
with perforating or subsequently, should be one of
the standard methods in the engineers bag. That is
not to say it should dominate the industry, but that
it should be thought of along with conventional
perforating, acidization, hydraulic fracturing, and all Myth: My propellant tool will frac all of these wells in one
of the other valid techniques one uses to make a job!
well better. Unfortunately, in the earlier days of pro- view of the issues. But it is to say that too often,
pellants, and even continuing until today, too many the need for good science and engineering has
proponents have succumbed (some unknowingly) been replaced with the need to promote.
to the snake oil approach. They have promulgat- Let me share some of my observations with you.
ed myths and misconceptions which, instead of In all cases, my explanations are based on physical
growing the industry, have restricted it. Believing in principles, observations, field data, laboratory data,
myths leads to results not measuring up to promis- and computer modeling that agrees with both
es, or to downright failures. field and laboratory data. My explanations are not
That is not to say the purveyors of myths and guaranteed to be correct, but they surely are better
misconceptions are bad guys. By far, most of them than the unsupported presumptions leading to
are well-meaning and just trying to promote a most of the myths and misconceptions.
technology they believe in, or justify their own

Myth
Propellant tools can create fractures that are hundreds of feet long.

Reality Explanation
Depending on tool, tamp, rock and depth, pro- Some people like to make strong claims.
pellant fracture lengths are generally in the Others observe some pressure response in
range from a few feet to a maximum, under
nearby wells that are hundreds of feet away and
the very best of conditions, of a few tens of
interpret it as a fracture connection. It is
feet.
common that pulse-like pressure disturbances in
liquid reservoirs can create temporary transients
in nearby wells. This happens all the time in
earthquake-prone regions. It does not mean
these wells have been fracture connected,
unless a coincidental fault pre-exists.
Overly simplified mathematical models based
on elastic fractures use mass balance,
complete containment, zero leakoff, and high
moduli to show long fractures. These are
completely unrealistic because the factors left
out have a dominant effect on length, and all
tend to reduce length.

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Misconception
Bigger is better. Put the biggest propellant tool possible in the hole.

Reality Explanation
Overly large propellant tools can damage casing When a tool burns, energy can go into the forma-
and equipment. Even if damage is not done, an tion and up and down in the well, depending on
overly large tool will simply send most of its ener- a number of factors such as depth, liquid type,
gy up and down in the well and not out into the perf area, and formation properties. All of this
formation. depends on high-pressure fluid flow rates. If the
perfs and fracs have reached a limiting flow rate,
the release of more burn energy is simply expend-
ed in compressing and accelerating liquid in the
hole. Bigger is not better. Tool optimization with
good design is best.

Misconception
My propellant makes more gas than yours, therefore, it is better.

Reality Explanation
More gas does not automatically mean better See the previous misconception. It is possible with
stimulation performance. The trick is to get the any propellant that you can ignite downhole to
energy into the perfs and fractures. provide sufficient energy with adjustment of tool
size and other parameters. Propellant energy (per
pound) is of secondary importance. Furthermore,
some propellants that make more gas are also
potentially less stable.

Myth
All propellants are unreliable. You cant keep them from blowing up the casing or crushing the rock.

Reality Explanation
With quality control and quantitative design based Early experiments with more exotic materials,
on data, you will not damage casing or crush the such as pumpable explosives, highly energetic
rock. propellants, exotic ignition systems, and activators
caused some problems. It turns out that the extra
energy released by these is not needed. The more
conventional propellants are well-understood and
very controllable. The working range of burn rates
that can make fractures and still not damage wells
or formations is fairly broad and achievable with
good design.

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G e n e r a l I n t e r e s t a n d W h a t s N e x t

Misconception
This propellant looks like a piece of plastic. It cant have enough energy to do anything.

Reality Explanation
These pieces of plastic release nearly as much This is the opposite of the previous myth.
chemical energy per pound as explosives, but Propellant energies are known and measured.
at a lower rate. The additional good news is that despite the
high energy content, most propellants are very
difficult to light up and burn at a dangerous
rate under surface conditions. They are there-
fore somewhat safer than explosives (although
they should always be handled with appropri-
ate care).

Misconception
I tried some propellant in my well and it didnt help. Therefore, propellants dont work.

Reality Explanation
This is the common fallacy of generalization. There are some applications in which propel-
lants will not help. You cannot use one misap-
plication to judge an entire technology, and yet
this has been done.

Misconception
Propellants make multiple radial fractures. I have heard that these kinds of fractures are bad for
hydraulic fracturing. Therefore I would not consider using a propellant prior to my frac job.

Reality Explanation
Yes, propellants make multiple radial fractures, Tortuosity is a catch-all term used to describe
although the bi-wing that is stress-preferred is near-wellbore restrictions that create high frac-
longest. However, the most important thing turing pressures, poor flow, and premature
that propellants do prior to hydraulic fracturing sandouts. One of the host of things that is used
is to break down the majority of perforations to describe possible tortuosity creation is radi-
and make the most preferred able to accept al fractures. Multiple fracturings with convo-
fracture fluids earlier in the job. Propellants luted near-wellbore geometry, that all accept
help, not hurt hydraulic fracturing. flow equally (and poorly) are certainly not
good. Propellants, which can pre-create cleanly
broken down perfs, can return the well to the
condition best for hydraulic fracturing. If almost
all perfs are broken down, then the best, most
ideally oriented perfs will take fracture fluid
first. Propellants, therefore, are tortuosity
reducers, not tortuosity increasers.

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Misconception
A given propellant tool burns at a given peak pressure. When the pressure begins to decline the burn is
done.

Reality Explanation
Peak pressure is the result of a coincidence of sev- Peak pressure is determined by a balance of burn
eral factors. Burn can continue well after peak gas creation, fluid acceptance by the perfs/forma-
tion, and compression and motion of wellbore flu-
pressure is reached.
ids. If the formation accepts burn products, pres-
sure can decline while burn continues. These phe-
nomena emphasize the need for design calcula-
tions supported by prior data to predict peak
pressure burn durations and tool effectiveness.

Misconception
I have been told that four perf shots per foot are adequate for all propellant treatments.

Reality Explanation
There is a minimum acceptable perf area for all Because of the balance of burn, flow, compres-
treatments. It depends on hole size as well as hole sion, and fracturing, a single perf geometry is not
density. It depends to a lesser extent on penetra- always best. With design and experience in a
given area, the optimum can be determined.
tion, but penetration is not completely unimpor-
tant. In a few cases, two shots per foot may be
enough. Often, four shots per foot are adequate.
Frequently, six shots per foot are best.

Misconception
Since hydraulic fractures can initiate from the microannulus and not necessarily from a perf, improving perf
tunnel breakdown will not help my frac job. I dont need propellants.

Reality Explanation
Pre-treatment with propellants have improved the Good laboratory research has demonstrated that
initiation of many, many fracture jobs. In fact, this the microannulus effect exists for the slow flow
is one of the most common successes of the tech- regime at the inception of a conventional
nology. If the misconception were true, propel- hydrofrac. However, propellants create a very fast
lants would never create improvement in flow regime in which the microannulus cannot
hydraulic fracturing. accept fluids rapidly enough to dominate the flow.
Therefore, the propellant effectively pressurizes
the perf tunnel until breakdown. A propellant-
generated perf breakdown looks more like the
ideal situation a relatively clean fracture emanat-
ing from the perf tunnel face. This in turn can
accept the subsequent fracture fluid flow instead
of the microannulus because it is already broken
down and is the route that requires less work for
fracture entry or subsequent extension.

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G e n e r a l I n t e r e s t a n d W h a t s N e x t

Misconception
Who cares if propellants make fractures? Since they are not propped they will soon heal and become
ineffective.

Reality Explanation
Many propellant jobs have shown sustained Propellant-induced fractures can be partially
skin reductions and production increases for propped and opened due to erosion, ablation
periods of years. Furthermore, some applica- debris deposition, and shear offset. Indirect evi-
tions, such perf breakdown prior to subsequent
dence indicates that this happens. However,
fracture or acid treatment, do not require that
the magnitude of these effects remains unmea-
fracs remain open for extended periods.
sured, and this is an area where more research
is required in order to make quantitative pre-
dictions of permanent fracture widths created
by propellant fractures.

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Benefits of using high-speed gauge

data to obtain rock properties
John Gilbert, Marathon Oil Company
John Schatz, John F. Schatz Research & Consulting, Inc.
David Cuthill, Computalog Wireline Services
Bob Haney, HTH Technical Services, Inc.

M inifracs are used to assist with the main hydraulic

fracture design by generating estimates of fluid
efficiency, closure pressure, fracture geometry, and
Method
Propellant stimulation devices are routinely used for
near-wellbore cleanup and enhancement. One of the
leak-off coefficient prior to the main treatment. primary applications is for perforation breakdown and
Closure stress or minimum horizontal stress is fre- fracture initiation. Propellant initiates formation break-
quently determined by analyzing the pressure leak-off down, allowing successful fracturing at lowered initiation
response after pump shut-down using a Nolte-G func- pressures. As the propellant rapidly burns, high-pressure
tion analysis plot. Comparison of the measured data combustion gases are generated. These gases exert a
with the dimensionless Nolte-G time indicates closure pressure load on the formation, which can exceed the
when used in combination with the derivative and tensile strength of the rock resulting in fracture initia-
pressure superposition derivative. tion. Fracture growth is maintained by continued gas
The use of a high-speed digital pressure data generation from the tool burn. Once the tool is spent,
recorder during well perforating/propellant treat- the driving force for fracture growth is removed and
ments provides a new field technique to determine the pressure response is strictly related to gas leak-off
closure stress using the G-function and associated (Figure 1). As gas pressure decreases, energy sustain-
methods. By using a high-speed digital pressure data ing the fracture reduces to the point at which the
gauge, the fall-off pressure from the event, although fracture closes. The change in geometry or flow area
lasting only a few hundred milliseconds, has been results in a change in the rate of leak-off (Figure 2).
shown in special cases to provide sufficient closure Since a small fracture is normally generated during
information. Results have been consistent with other the stimulation operation, information about the for-
methods and this new technique can give a quick mation is captured as subtle variations in the pressure
estimate of closure stress prior to hydraulic fracturing response measured by a high-speed pressure
while equipment is in place in the field. recorder. This data can be used in a similar manner to

70 Figure 1
65 Gething Propellant
60 2220.5 - 2223.0 m (Perf.)
pressure vs. time
2220.8 - 2222.8 m (Prop.)
55 104.8 mm x 2.0 m Sleeve curve
50
Burn ends
45 0.070 s / 43.5 MPa
Pressure (MPa)

40
35
30
25
20
15
10
5
0
-0.05 0 0.05 0.1 0.15 0.2 0.25
Time(s)

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G e n e r a l I n t e r e s t a n d W h a t s N e x t

Closure stress
Estimated at 33 MPa
(4732 psi)

minifracture data to assist with formation mechan- from previous field experience. Pressure recorder
ics determination using the G-function method. data indicated that this was a good candidate for
Using the superposition derivative magnifies the determination of the formation closure stress.
subtle slope changes in pressure response assisting
the location of the point of closure, which is
related to the minimum horizontal stress. The high-speed data from
Benefit propellant breakdown looks
An estimate of closure stress is important equivalent to a normal
for proper hydraulic fracturing design. The
ultimate advantage of obtaining closure
hydraulic fracturing
stress at the time of perforating/propellant G-function.
stimulation is a significant cost savings
because the data can be obtained in the John Gilbert
normal course of the completion operation.
A superposition derivative of the G-function
Example was applied to the data to make the
A StimGun assembly was used to assist determination of closure stress. Closure is
hydraulic fracture breakdown. The well was devi- determined as the point at which the superpo-
ated, and experience in the area indicated that sition derivative (GdP/dG) drops off after
this normally contributed to higher hydraulic frac- completion of the propellant tool burn.
turing breakdown pressures. Normally observed From this plot closure (Figure 2) stress is
breakdown pressures range from 6900 to 7250 psi estimated to be 4728 psi (33 MPa).
(47,000 to 50,000 kPa). Propellant-assisted perfo- Based on the depth of the well, and applying a
rating was used to clear the perforations and minimum horizontal stress gradient estimate of
lower the breakdown pressure. A subsequent 0.65 psi/ft (1.4 kPa/m), closure pressure is
gelled hydrocarbon fracture broke down at estimated at 4734 psi (33 MPa) at downhole
6200 psi (42,700 kPa) a substantial reduction conditions.

50 25
Gething Figure 2
45
2220.5 - 2223.0 m (Perf.) Nolte-G function
2220.8 - 2222.8 m (Prop.)
40 20 plot of Figure 1
104.8 mm x 2.0 m Sleeve
dP/dG & GdP/dG

35 data showing
Pressure (MPa)

fracture closure.
30 Closure stress 15
Estimated at 33 MPa
25 (4732 psi)

20 10

15

10 5

0 0
0 0.5 1 1.5 2 2.5 3 3.5 4
Nolte-G Time
Press. dP/dG

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New product and technology

development
John Schatz, John F. Schatz Research & Consulting, Inc.
Joe Haney, HTH Technical Services, Inc.

T he goals of Propellant Technology Development

Group are to not only to manufacture, supply,
and support the existing products, but also to devote
methods because dynamic tools, with their high
loading rates and peak pressures (but low-time dura-
tions) affect wellbore equipment, tubular hardware,
resources to the following: cement, and producing formations differently than
Product optimization low-speed quasi-static industry methods. For exam-
ple, we know that good-condition casing can with-
New product development stand significantly higher differential pressures than
Innovation in dynamic stimulation methodology handbook burst values when only loaded for 10 ms.
To achieve these goals, we must constantly main- We are not exactly sure what the increased dynamic
tain awareness of licensee and industry needs, review strength is and how it is affected by load duration
manufacturing and distribution procedures, test prod- and other factors.
ucts in the laboratory and in the field, and improve To address this need, the group has embarked upon
hardware and software to keep it state-of-the-art. a program to develop a surface dynamic testing facili-
ty. The conceptual design of this facility has been com-
New dynamic testing facility pleted and several tests have been run in prototype
While developing, testing, and deploying products, configurations. The basic concept of the facility is to
and with the assistance of licensees, the group has allow tools and hardware (such as casing and packers)
realized that almost no industry-standard testing to be tested at the differential pressures and for the
methods exist for the evaluation of high-speed time durations (in the range 10 to 100 ms) they
(dynamic) stimulation tools. There is a need for such would see in dynamic field opera-
tions. An integral part of the facility
will be the ability to measure pres-
sures and deformations (strains) in
this time range. Special computer
code methods will allow data and
results to be compared and find-
ings extrapolated to a wide variety
of downhole conditions.
Some of the specific planned
activities for this facility are:
Establish dynamic ratings for
casing, packers, plugs, etc.
Develop methods for pressure
wave control to reduce
equipment impact.
Develop methods of dynamic
fluid flow modification to
improve tool performance and
reduce tool motion.
Figure 1 Pressure vs. time for a 2 in. (51 mm) StimTube tool at surface in 412 in. Evaluate new products and
(114.3 mm) casing. Blue line in upper graph is data at pressure gauge port compared components to improve
with computer simulation in red. Black line in lower graph is computer simulation at performance and/or reduce
tool center. costs.

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G e n e r a l I n t e r e s t a n d W h a t s N e x t

StimGun
Dynamic Casing Ratings This effect can be used to reduce operational prob-
As part of the prototype facility development, the lems as well as create dynamic underbalance in an
initial instrumented tests have been successfully otherwise balanced or overbalanced situation.
conducted to develop a dynamic pressure burst rat-
Dynamic flow modification
ing for casing. Figure 1 shows the pressure versus
time record and computer simulations for a Several methods will be investigated of modify-
2 in. (51 mm) OD x 36 in. (.91 m) length ing the dynamic flow near to a tool to improve
StimTube tool in water-filled 412 in. (114.3 mm) performance and reduce the potential of opera-
N-80 casing. Casing burst was exceeded by a factor tional problems. These include the use of special
of 1.6 for about 10 ms and failure did not occur. diverters and reflectors.
Tests in this series will continue to fully develop Product and component development
the facility and to create a series of dynamic casing
test evaluations that can be used for job design. Work in this area will include:
New tool sizes
Pressure wave control
Propellant formulations requiring minimal
Several methods are being evaluated of control-
liquid tamp
ling and attenuating pressure waves that have the
potential of adversely damaging packers, plugs and Novel use of proppants
other equipment. Figure 2 shows a small pressure Tools containing tracers
vessel (chamber) is opened up by a perforating
Internal sleeve StimGun assemblies
charge that does not penetrate the outer casing.
Rapid fluid flow into the chamber results in a tem- Novel tool geometries and types for long
porary pressure reduction lasting about 15 ms. horizontal holes and tubing-size limited work

6500

6000
Pressure psi

5500

5000

4500

4000
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Time seconds

Figure 2 Dynamic pressure decrease resulting from the rapid opening of a chamber inhole. In the example, the pres-
sure decreases by more than 1000 psi for about 15 ms.

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The StimGun technology has been a

collaborative effort of a multitude of
companies and people. The perspec-
tives and input from these various
sources continues to improve the
overall portfolio. The authors of this
publication hope the readers will
consider incorporating StimGun
technology in well completions.

While Mission Statements have

certainly decreased in popularity
over the past few years, this groups
statement has always remained the
same:
Develop successful applications
for the propellant technology in
the oil and gas industry.
Maintain safety as the highest
priority.
Establish a high trust relationship
with the industry, our customers,
and each other.
Build a profitable business oppor-
tunities for the stakeholders of the
technology.
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Appendix I: Glossary

Abalation debris Small pieces of broken rock caused by high-speed fluid flow at an exposed surface,
such as a perforation tunnel entrance or fracture face.
Absolute Permeability A measure of the ability of a single fluid (such as water, gas, or oil) to flow
through a rock formation when the formation is totally filled (saturated) with that fluid.
Acidizing Treating hydrocarbon-bearing formations with acid for the purpose of increasing production.
Acid is injected into the formation under pressure and etches the rock, enlarging the pore spaces
through which the reservoir fluids flow. Acid also removes formation damage by dissolving materials
plugging the rock around the wellbore.
API American Petroleum Institute.
Back-flushing The reverse flow of propellant-driven gases and liquids leaving the perforation tunnel and
moving back into the well.
Bar-vent A device used in underbalanced perforating operations that functions as a valve and is actuat-
ed by a tubing-conveyed drop bar.
bbl Barrel
Big-block surface test A surface test involving a large concrete test cylinder, similar to an API perforat-
ing target, in which test tools are fired and fracturing results observed.
bht Bottom hole temperature.
bhp Bottom hole pressure.
bha Bottom hole assembly.
btu British Thermal Unit, a unit of heat energy.
bopd Barrels of oil per day.
bofpd Barrels of fluid per day.
bpd Barrels per day.
bowpd/bwpd Barrels of water per day.
Bridge plug A type of plug used to seal off a well temporarily while the wellhead is removed. Also used
to seal off or isolate a particular zone for acidizing, testing, cementing, etc. Most bridge plugs are
meant to be removable.
Cased hole A drilled hole lined with a steel pipe the purpose of which is to prevent the wall of the
borehole from caving in, to prevent movement of fluid from one formation to another and to
improve the efficiency of extracting hydrocarbons if the well is productive. Normally the pipe is sur-
rounded by cement to hold it in place and seal it.
Crush zone The region of reduced permeability surrounding a perforated tunnel and resulting from the
extreme pressure effects of the perforating jets on the rock.
Darcy A unit of measure of permeability. The permeability of most reservoir rocks is usually measured in
millidarcys (md), or thousandths of a Darcy.
Darcys law An empirical but well-accepted law stating that the rate of flow of a fluid through a rock is
proportional to the applied pressure gradient divided by the viscosity, or flow resistance, of the fluid.
The constant of proportionality is called permeability.

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Drill stem test (DST) A common method of formation testing where drilling is stopped and the drill pipe is
used as the flow conduit. The DST is not as accurate as some other methods, but it is quick and relatively
inexpensive.
Drop bar A cylindrical steel rod used to actuate downhole equipment such as firing heads and vents. It is
dropped from the surface down the wellbore, falling through the well fluid until it strikes the device it is
intended to actuate.
Dynamic event Refers to events that have a duration of up to about a few hundred milliseconds.
Dynamic fracturing Fracturing that occurs in less than a few hundred milliseconds.
Dynamic loading Loading that occurs in less tan a few hundred milliseconds; also refers to exerting repeti-
tive force such as cyclical stressing.
Early leak-off Fracturing fluid that prematurely leaves the fracture and starts to enter the formation, and
which can inhibit fracture growth.
Leak-off test The gradual pressuring of the casing after the blow-out preventer has been installed to permit
estimation of the formation fracture pressure at the casing seat.
Leak-off rate The rate at which a fracturing fluid leaves the fracture and enters the formation surrounding
the fracture. Generally, it is desirable for fracturing fluid to have a low leak-off rate (i.e. very little fluid
should enter the formation being fractured), so that the fracture can better extend into the formation.
Effective permeability A measure of the ability of a single fluid to flow through a rock when another fluid is
also present in the pore spaces.
EOB Extreme overbalance. Fluid pressure in the well before the job is much greater than formation pressure,
usually enhanced by pumping at the surface. This causes a surge flow into the formation when the perfo-
rations are opened.
Explosive fracturing Explosives used to fracture a formation. After detonation, the explosives furnish a source
of high-pressure gas to force fluid into the formation. Undesirable effects include reduced borehole integri-
ty, casing damage, cement damage, and rock crushing.
Filter cake Solids left on or slightly penetrating the rock face after drilling, caused by drilling fluids flowing
into the rock and leaving behind fine entrained particles as a cake. The remaining fluid is called filtrate.
Firing head The component used to ignite the explosive train in perforating guns, StimGun assemblies, or
propellant-stick tools.
FMI log Formation Micro Image. A multi-pad logging tool measuring formation resistivity simultaneously at
many points, resulting in a resistivity map of the very near-wellbore, often used for natural and induced
fracture detection.
Fracture gradient The pressure-to-depth-ratio at which a formation will fracture.
Formation evaluation The analysis of subsurface formation characteristics, such as lithology, porosity, perme-
ability , and saturation by indirect methods such as wireline well logging or by direct methods such as
mud logging and core analysis.
Fracture pressure The pressure at which a formation will fracture from pressure in the wellbore. (See fracture
gradient.)
Formation fracturing A method of stimulating production by opening new flow channels in the rocks sur-
rounding a production well.
Formation resistivity A measurement of the electrical resistance of a formation, strongly affected by the type
of fluid in the pore space.

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Formation sensitivity The tendency of certain producing formations to react adversely to invading fil-
trates. (See filter cake).
Frac Common abbreviation for fracture.
Frac fluid The fluid used in the hydraulic fracturing process, including liquids such as water, distillate,
diesel fuel, crude oil, dilute hydrochloric acid, and kerosene.
G The acceleration of gravity measured in ft/s2, m/s2 (1 G = 32 ft/s2 = 9.8 m/s2)
G-function Dimensionless function which looks at shut-in time normalized to pumping time. It is used
to analyze pressure-dependent leak-off.
Heavy oil sands Deposits of bitumen, a tar-like mixture of hydrocarbons, so heavy and viscous that it
must be heated or diluted with lighter hydrocarbons in order to flow. Found mainly in Canada and
Venezuela.
Hydraulic fracturing An operation in which frac fluid is pumped downward through tubing or drill
pipe and forced out through perforations below or between two packers. Often propping agents are
carried in suspension by the fluid into the cracks. When the pumping ceased, releasing the pressure
at the surface, much of the fracturing fluid returns to the well but leaves behind the propping agents
to help maintain the opening of the formation cracks. Then hydrocarbons from the formation flow
back through the cracks and into the well.
Hydrostatic pressure The force per unit area exerted by a body of fluid at rest at a given depth.
Increases directly with the density; typically expressed in lb/in2 or kPa.
Hz Hertz, the unit of frequency in cycles/second.
Injectivity The measurement of the ability to inject fluids into a well/formation.
In-situ stress The stresses imposed by the weight of a geologic body and tectonic forces on the rock at
depth. In equilibrium these stresses are usually expressed as the three orthogonal principle stresses
called greatest, intermediate, and least. In a vertical well deeper than about 2,000 ft (610 m), the
greatest stress is typically the vertical stress. The least is one of the horizontal stresses. Without addi-
tional influence causing local stress concentrations, fractures from the well will usually initiate first in a
direction perpendicular to the least in-situ stress.
KCl water An aqueous solution of potassium chloride frequently used as a completion fluid.
Kilopascal kPa, 1000 Pascal, a metric unit of measurement for pressure and stress.
mcfgpd Thousand cubic feet of gas per day.
Millidarcy A unit of permeability equal to 1/1000 of a Darcy.
Minifrac A small preliminary fracture job used as a test to help determine the parameters necessary to
design a full-scale fracture job.
mmscfd Million standard cubic feet per day.
MPa Megapascals, 1 million Pascals (see Kilopascal).
ms Millisecond equal to 1/1000 of a second.
Near-wellbore damage Damage which occurs within several feet of the wellbore and caused by the
migration of small particles and adverse fluids into the formation.
NH4Cl Ammonium chloride
Nolte-G function A dimensionless measure of time often used in analyzing pressure behavior during
fracturing.

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Non-stress preferred fracture A fracture that propagates in a direction not perpendicular to the least princi-
ple in-situ stress. (See in-situ stress.)
OD/ID Outside diameter/ inside diameter, usually used in reference to pipe dimensions.
Open hole Any well or portion of a well in which casing is not suspended in the wellbore.
Oxidizer A chemical containing releasable oxygen that must be present in order to make fuel burn when not
in the presence of air.
Packer A cylindrical item of downhole equipment that consists of a sealing device, a holding device, and an
inside passage for fluids. In open holes, it is used to block the flow of fluids through the annular space
between the pipe and the wall of the wellbore. In cased holes, it is used to support tubing and constrain
the flow of fluids to the interior of the tubing.
Perf A commonly used abbreviation for perforation.
Perforating gun A device fitted with shaped explosive charges or (less commonly) bullets that is lowered to
the desired depth in a well and fired to create penetrating holes in the casing, cement and formation. The
holes in the formation are commonly called tunnels and may extend from less than one foot to several
feet in depth.
Perforation breakdown The fracturing of the wall of a perforation tunnel. This is a necessary process at the
inception of a hydraulic or a propellant fracture.
Permeability A measure of the ease with which a fluid flows through the connecting pore spaces of rock or
cement. (See Darcys law.)
Plug Any object or device that blocks a hole or passageway.
Plug-back To place cement or other plugging material in or near the bottom of a well to exclude bottom
water, to sidetrack or to produce from a formation higher in the well.
Poissons ratio When a rock is compressed axially, this is the ratio of longitudinal compressive strain to the
transverse extensional strain. Poissons ratio must be in the range 0 to 0.5.
Porosity Ratio of the volume of empty space to the volume of solid rock in a formation, indicating how
much fluid a rock can hold.
Pow*rPerf A proppant release canister used in conjunction with TCP with extreme overbalanced pressures
in the tubing. A Marathon Oil Company service marked product and procedure.
Propellant Generally a mixture of fuel and oxidizer that burns rapidly when ignited, but does not form a
shock wave and detonate, thereby becoming an explosive. A substantial portion of the burn products are
usually expanding gases.
Proppant A granular substance that is carried in suspension by the fracturing fluid and that serves to help
keep the cracks open when after the fracturing treatment is done.
psig Abbreviation for pounds per square inch gauge. Typically, a gauge will read zero at the surface, while
absolute pressure is the pressure of the atmosphere. Thus under these conditions gauge pressure and
absolute pressure will differ by about 15 psi.
Relative permeability The ratio of effective permeability to absolute permeability. The relative permeability
of rock to a single fluid is defined as 1.0 when only that fluid is present, and 0.0 when the presence of
another fluid prevents all flow of the given fluid.
Resistivity An electrical resistance offered to the passage of current; the opposite of conductivity.
Rock Shear strength The stress at which a rock fails under shearing (distortional) load. When the average
load is compressional, as is usual underground, this is synonymous with compressive strength.

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RTD Resistive thermal device, often used for temperature measurement.
SBHP Shut in bottom hole pressure, the pressure at which the well and the formation are in equilibrium.
SCF Standard cubic feet. Unit of measure of gas quantity at atmospheric pressure. Common prefixes
are MM million, B billion and T trillion.
Screen-out To plug a well inadvertently with proppant during fracturing operations. Screen-out is usu-
ally the result of a reduced fluid velocity allowing the proppant to become separated from the fluid
instead of being carried away from the well bore and into the fracture.
Skin Used to describe the impediment to the flow of fluids to the well caused by near-wellbore restric-
tions. A perfect well will have askin of zero. A restricted well will have a positive skin. A stimulated
well will have a negative skin.
Skin frac A small fracture job intended to reduce or eliminate skin.
Slickline A thin nonelectric cable used for placement and retrieval of wellbore hardware.
Spectral GR image Gamma Ray which splits the spectrum into three natural energy level, spectrum:
Uranium, potassium, and thorium.
spf Abbreviation for shots per foot, used to denote the number of perforations per foot of casing.
spm Abbreviation for shots per meter, used to denote the number of perforations per foot of casing.
Swab A hollow rubber-faced cylinder mounted on a hollow mandrel with a pin joint on the upper end
to connect to the swab line. The swab is used to remove liquid from the well, usually with the intent
of initiating natural flow.
Surge tool A downhole tool that is used to create a sudden decrease in pressure at the bottom of the
wellbore.
Tamp The liquid that must be emplaced about a propellant tool to get it to burn rapidly. The term is
borrowed from the explosives industry, which uses tamps to help contain explosive energy within a
borehole.
TCP Abbreviation for tubing-conveyed perforation.
Tensile extension The stretching of a material in pure tension.
Tortuosity Technically, the amount of bending and twisting in a path that a liquid must take in a
porous media, thus acting as an impediment to flow. In practice, a catch-all term used in the fractur-
ing industry to express general restrictions to flow near to the wellbore that can have adverse affects
on a fracturing job.
Tracer log A survey that uses radioactive tracers placed by pumping, usually during fracturing opera-
tions, to determine the vertical extent of fracturing effectiveness behind perforated casing, or if frac
fluid was forced into uncemented or poorly cemented zones.
TVD Abbreviation for true vertical depth, the actual vertical depth of a position within a deviated or
horizontal well.
Underbalanced The condition in which pressure in the wellbore is less then the pressure of the forma-
tion.
Water flood A method of improved recovery in which water is injected into a reservoir to drive addi-
tional quantities of oil that have been left behind after primary recovery to production wells.
Wireline Braided wire cable with embedded electrical conductors used for placement and retrieval of
wellbore hardware. (See slickline.)

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Appendix II: References

Christianson, M.C., R. Hart and J.F. Schatz, (1988) Numerical Analysis of Multiple Radial Fracturing,
in Key Questions in Rock Mechanics, Proc. of the 29th U.S. Symposium on Rock Mechanics,
Minneapolis, MN.

Cuderman, J.F.: Design and Modeling of Small Scale Multiple Fracturing Experiments, Sandia Report
SAND1-1398, Sandia National Laboratories, Albuquerque, NM (1981).

Cuthill, D. and Haney, R., Advances in High Energy Gas Stimulation Techniques, paper 99-139 pre-
sented at the 1999 CADE/CAODC Spring Drilling Conference, Calgary, Canada, 7-8 April.

Cuthill, D. and Haney, R., Advances in High Energy Gas Stimulation Techniques, presented at
EXITEP-98, 15-18 November 1998, Mexico City, Mexico.

Cuthill, D. and Haney, R., Utilizing high speed pressure recorders to determine rock properties, pre-
sented at the 1998 GeoTriad conference, Calgary, Canada.

Cuthill, D., Propellant Assisted Perforating An Effective Method for Reducing Formation Damage
When Perforating, paper SPE 68920 presented at the SPE European Formation Damage
Conference held in The Hague, The Netherlands, 2122 May 2001.

Cuthill, D., Miller, K., and Webb, T., System Fuses Perforating, Stimulation, September 1998 article
from American Oil & Gas Reporter, page 143-145.

Cuthill, D., Schatz, J., and Gilbert, J., A New Technique for Rapid Estimation of Fracture Closure Stress
When Using Propellants, paper SPE/ISRM 78171 presented at the SPE/ISRM Rock Mechanics
Conference held in Irving, Texas, 20-23 October 2002.

Daehnke, A., H.P. Rossmanith, and J.F. Schatz (1997), On Dynamic Gas Pressure Induced Fracturing,
Fragblast, 1,1, pp. 73-98, Balkema, Rotterdam

El-Bermawy, H., and H. El-Assal, A Unique Approach to Enhancing Production from Depleted, Highly
Laminated Sand Reservoirs Using a Combined Propellant /Perforating Technique presented at
the 2001 SPE Middle East Oil Show, 17-20 Mar, 2001.

Folse, K., Dupont, R., and Coats, C., Field Performance of Propellant/Perforating Technologies to
Enhance Placement of Proppant on High Risk Sand-Control Completions, paper SPE 71639
presented at the 2001 SPE Annual Technical Conference and Exhibition held in New Orleans,
Louisiana, 30 September3 October.

Gilliat, J. Self-stimulating Perforator Enhances Frac Job, December 2000 article from WorldOil maga-
zine.

Gilliat, J., Snider, P., and Haney, R., A Review of Field Performance of New Propellant/Perforating
Technologies, paper SPE 56469 presented at the 1999 SPE Annual Technical Conference and
Exhibition held in Houston, Texas, 36 October.

Halleck, P.M., J. Robins, L. Pekot, and J. Schatz: Mechanical Damage Caused by Perforations May
Affect Fracture Breakdown , SPE 51051 presented at 1998 SPE Eastern Regional Meeting,
Pittsburgh, PA (Nov, 1998).

Haney, B.L. and Cuthill, D.A.: The Application of an Optimized Propellant Stimulation Technique in
Heavy Oil Wells, paper SPE 37531 presented at the 1997 SPE International Thermal
Operations & Heavy Oil Symposium, Feb. 10-12.

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Hanson, J.M., Schmidt, R.A., Cooley, C., and Schatz, J. (1984), Multiple Fracture Stimulation Using
Controlled Pulse Pressurization, SPE/DOE/GRI 12839, in Proc. of the 1984 SPE/DOE/GRI
Unconventional Gas Recovery Symposium, Pittsburgh, PA.

Hunt, W.C., and W.R. Shu: Controlled Pulse Fracturing for Well Stimulation, SPE 18972 presented at SPE
Joint Rocky Mountain Regional/Low Permeability Reservoirs Symposium and Exhibition, Denver
(Mar 1989) 445.

Miller, K.K., Prosceno, R.J., Woodruff, R.A., and Haney, R.L.: Permian Basin Field Tests of Propellant- Assisted
Perforating, paper SPE 39779 presented at the 1998 SPE Permian Basin Oil and Gas Recovery
Conference, Mar. 25-27.

Nilson, R.H., W.J. Proffer, and R.E. Duff: Modelling of Gas-Driven Fractures Induced by Propellant
Combustion Within a Borehole, Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. (1985) 22, No. 1,3.

Ramirez, J., Barrera, J., Romero, R., Figueroa, F., Almanza, E., and Folse, K., Propellant-Assisted Perforating
in High-Pressure and Temperature Wells at Campo Bosque in Northern Monagas State, paper SPE
71644 presented at the 2001 SPE Annual Technical Conference and Exhibition held in New Orleans,
Louisiana, 30 September3 October.

Schalgenhauf, M., New Propellant Stimulation Tools Quickly Increase Production, Drilling Wire December
8, 1999, Volume 38, Number 49.

Schatz, J. F. (1993), Modeling and Field Examples of the Dynamic Fracturing of Rock with Propellants, in
Proc. of the 4th International Symposium on Rock Fragmentation by Blasting, Vienna, Austria.

Schatz, J.F. (1991), Mathematical Modeling of the Dynamic Fracturing of Rock for the Petroleum Industry, at
Sixth Annual Conference of the European Consortium for Mathematics in Industry, Limerick, Ireland.

Schatz, J.F. and A. Czychun (1992), Formation Damage Cleanup by Dynamic Pulse Fracturing: Case Study
in Permeable Gas Sands, in 1992 SPE Formation Damage Control Symposium, Lafayette, Louisiana.

Schatz, J.F., and J.M. Hanson (1986), Multiple Radial Fracturing from A Wellbore Conceptual Model and
Experiments, in Proc. of the 27th U.S. Symposium on Rock Mechanics, 669-674, Tuscaloosa, AL.

Schatz, J.F., B.J. Zeigler, J. Hanson and M. Christianson (1987), Multiple Radial Fracturing from a
WellboreExperimental and Theoretical Results, in Proc. of the 28th U.S. Symposium on Rock
Mechanics, Tucson, AZ.

Schatz, J.F., B.J. Zeigler, J. Hanson, M. Christianson, J. Haney, and R. Bellman (1989), Laboratory, Computer
Modeling, and Field Studies of the Pulse Fracturing Process, in Proc. of the 1989 SPE Production
Operations Symposium, Oklahoma City, OK.

Schatz, J.F., B.J. Zeigler, R.A. Bellman, J.M. Hanson, M. Christianson, and R.D Hart (1987), Prediction and
Interpretation of Multiple Radial Fracture Stimulations, Final Report for Gas Research Institute (GRI)
Contract No. 5084-213-1149, Chicago, IL.

Schatz, J.F., Haney, B.L., and Ager, S.A., High-Speed Downhole Memory recorder and Software Used to
design and Confirm Perforating/Propellant Behavior and Formation Fracturing, paper SPE 56434,
Proc. 1999 Annual Conference and Exhibition, (October 1999).

Schatz, J.F.: Prediction and Interpretation of Multiple Radial Fracture Stimulations, Gas Research Institute
86/0137, (1987).

Schatz, John F., (1992) Improved Modeling of the Dynamic Fracturing of Rock with Propellants, in Proc. of
the 33rd U.S. Symposium on Rock Mechanics, Santa Fe, NM.

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van Batenburg, D. et al, New Technique for Hydraulic Fracturing in the Hassi Messaoud Field, paper
SPE 63104 presented at the 2000 SPE Annual Technical Conference and Exhibition held in
Dallas, Texas, 1-4 October 2000.

Waheed, A., El-Assal, H., Negm, E., et al, Practical Methods to Optimizing Production in a Heavy-Oil
Carbonate Reservoir: Case Study From Issaran Field, Eastern Desert, Egypt, paper SPE 69730
presented at the 2001 SPE International Thermal Operations and Heavy-Oil Symposium,
Margarita Island, Venezuela, 12-14 March.

Whisonant, R.J., and Hall, F.R., Combining Continuous Improvements in Acid Fracturing, Propellant
Stimulation, and Polymer Technologies to Increase Production and Develop Additional
Reserves in a Mature Oil Field, paper SPE 38789, Proc. 1997 SPE Annual Technical
Conference and Exhibition, San Antonio, TX, October 1997.

Zeigler, B., J. Schatz and E. Nudd, (1988) A Comparison of Multiple Radial Fracturing Enhancement
Techniques Laboratory Investigation. in Key Questions in Rock Mechanics, Proc. of the
29th U.S. Symposium on Rock Mechanics, Minneapolis, MN.

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Appendix III: Contributing Authors

Biographies
Members of the Propellant Technology Development Group
Scott A. Ager
Vice President
Instrumentation and Engineering Services, Inc. (IES)

Scott is a one of the owners of Instrumentation USAF Armament Laboratory at Eglin AFB, he
and Engineering Services, Inc. (IES), based in Ft. designed and developed the Electromagnetic
Walton Beach, Florida. He specializes in electronic Launcher (EML) projectiles, soft catch systems for
high-shock instrumentation systems and has been projectile recovery, and system integration of a
a high shock instrumentation engineer for the sev- high-shock instrumentation recorder, projectile,
eral companies, as well as with the Air Force since accelerometer, launcher, and soft catch. Scott
1984. Scott has been responsible for the design earned his B.S. in Electrical Engineering at
and build-up of instrumentation systems to collect LeTourneau College in 1984. His equivalent
acceleration/ deceleration profiles for projectiles minors were in Math, Mechanical Engineering,
ranging from 10 to 2000 lbs., penetrating con- and Computer Science.
crete walls more than six feet thick, resulting in Contact: Scott A. Ager
deceleration forces approaching 100,000 Gs. As IES, Inc.
an Officer in the United States Air Force, he was 151 Mary Esther Blvd., #311
the project engineer for the In-Bore Phone: 850-244-2128
Instrumentation/ Diagnostics (IBID) program in Fax: 850-244-7979
support of the Electromagnetic Launcher Branch, E-mail: scott@iesrecorder.com

David Cuthill
Engineering Manager
Computalog Wireline Services
Calgary, Alberta, Canada

David Cuthill is Engineer Manager - Emerging breadth of experience in the application and analysis
Technologies for Computalog Wireline Services, of numerous other cased hole logging services.
and is based in Calgary, Alberta, Canada He serves David holds a Bachelor of Science degree in
as the companys propellant services champion Chemical Engineering from the University of
and provides technical support for cased hole Saskatchewan and is a member of the Association
wireline services; with over 17 years experience. of Professional Engineers, Geologists, and
He has been involved with propellant stimulation Geophysicists of Alberta, the CIM, and the Society
services and applications since 1990 with active of Petroleum Engineers. He has authored a num-
involvement in propellant job design, high speed ber of papers on propellant stimulation and relat-
pressure recorder analysis, and PulsFrac computer ed technologies
simulations. During this time he participated in the
Contact: David Cuthill
initial adaptation and development of the high-
Computalog Wireline Services
speed recorders for propellant and perforating
4500, 150-6th Avenue SW
applications, high-speed pressure data analysis
Calgary, AB T2P 3Y7
techniques, and the StimGun assembly partici-
Canada
pating in the design and testing of the system.
Phone: 403-298-3883
David has extensive experience in wireline and tub- Fax: 403-266-2011
ing conveyed perforating applications; production log- E-mail: dave.cuthill@computalog.com
ging utilization, analysis, and interpretation; and has a

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Bob Daly
Senior Technician, Drilling and Completion Technology
Marathon Oil Company
Littleton, Colorado

Bob has had 12 years of experience with the instru- level. He presently develops solutions to many special-
mentation group at Marathons Petroleum ized field related data acquisition problems.
Technology Center in Littleton, CO. His expertise Bobs diverse background. The group can rely on
involves all phases of instrumentation including both him to function with minimal support.
hardware and software, lab experiment acquisition
Contact: Bob Daly
and control, seismic instrumentation support, and
Marathon Oil Company
specialized instrument development. He has extensive
7400 South Broadway
field experience with high speed pressure recorder
Littleton, CO 80122
development and field support. Bob has attended
Phone: 303-734-2252
vocational training in electronics and vocational train-
Fax: 303-794-1720
ing as a machinist. He has a patent on a gauge for
E-mail: radaly@marathonoil.com
specialized measurement of reservoir hydrocarbon

Janet Emr
Senior Engineering Technician
Marathon Oil Co

Janet Emr works in Marathons Drilling and Domestic Emergency Response Strike Team, which
Completion Technology Organization in Houston, responds to any environmental, political, or safety
Texas and part of her job responsibilities include incidents. Janet attended both William Woods
technology transfer. In this capacity Janet not only University and Southwest Texas State University grad-
coordinates seminars, publications, and some of uating with a Bachelors of Science degree.
Marathons technical peer groups, but also travels Contact: Janet Emr
extensively to the field when new technology is Marathon Oil Company
being implemented. She is the primary coordinator P O Box 3128
for many facets of the Propellant Technology Houston, TX 77253-3128
Development Groups activities. Prior to joining this Phone: 713-296-3347
organization, Janet worked as a technician in Fax: 713-296-3397
Marathons Environmental and Safety group. She is E-mail: jlemr@marathonoil.com
also a member of Marathons International and

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Bob Haney
StimGun Expert
HTH Technical Services, Inc.

Robert Haney is one of the principal propellant analysis of high-speed data. He has worked closely
team members and also is part of HTH Technical with the propellant team in developing the pres-
Services, Inc. Bob presently works for and with all ent package of tools and services.
of the propellant group members and license Bob has co-authored several SPE papers related
holders providing technical consulting for job sim- to propellant stimulation and is included in several
ulation, design and analysis. propellant related patents and patent applications.
Bob started his career in the oil industry at the His role in the group centers around the promo-
age of five when he washed and prepared sam- tion of proper technology utilization through edu-
ples of drill cuttings for his father (a well site geol- cation, data acquisition and analysis, and product
ogist). By the age of seven he had learned to iden- development.
tify the major rock types and look for hydrocarbon The propellant team members and the other
potential. Finishing his education (Fresno State licensees value Bobs experience as the person
University Geology major, organic chemistry who is probably involved with more of the job
minor), he returned to the oil industry where he designs and models than anyone else in the indus-
washed and prepared samples of drill cuttings for try. Some team member companies have internal
one year as a mud logger and two years as a well rules stating they will not execute a propellant
site geologist/engineer before progressing to drill stimulation without Bobs prior approval, and that
stem testing. He spent 14 years with a small DST alone is a tremendous compliment to his abilities
company running the day-to-day operations, per- and knowledge.
forming well test analysis, and designing tools. His
Contact: Bob Haney
development work on down hole electronic DST
HTH Technical Services, Inc.
recorders led to the initial work on high-speed
777 10th St. SW
high-shock instrumentation for use in down hole
Calgary, Alberta
explosive events. Since 1988 he has been involved
Canada T2P 5G3
in all aspects of propellant stimulation operations:
Phone: 403-261-7855
designing propellant ingredients/mix ratios and
Fax: 403-261-7855
tool configurations, preparing job proposals, man-
E-mail: bhaney@shaw.ca
ufacturing and transporting propellant, assem-
bling and arming guns, and the acquisition and

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Joe Haney
President
HTH Technical Services, Inc.

Joe Haney is the president HTH Technical Services, products. He has also been responsible for design of
Inc. and has the distinction of residing in the Idaho manufacturing processes/equipment, field testing,
oil capital of Coeur dAlene. He has been involved and continued product improvement. He is one of
the propellant stimulation industry since 1986. Joe the inventors of the StimGun assembly and
has been responsible for all facets of propellant stim- StimTube tool. HTH is the licensed manufacturer
ulation product/market development including pres- (sub-licensed to Owen Oil Tools) of both Marathon
sure gauge development, technical support, market- Oil Company well stimulation propellant products as
ing, field operations, tool design, and manufacturing. well as the HTH product WST. In terms of support
Joe obtained a B.S. degree in Geology in 1975. of the technology, Joes primary responsibility is to
Although his experience is varied within the oil and assist licensees in understanding the products how
gas, geothermal, and environmental industries, he has they are made, how they work, and where they work.
primarily been involved in pressure transient testing, Contact: Joe Haney
instrumentation development, drilling and sampling HTH Technical Services, Inc.
supervision, and product design/development. Joe 5893 Valley St.
spends 100% of his time developing propellant stim- Dalton Gardens, ID 83815
ulation technology. Phone: 208-772-5970
In terms of his role in propellant technology devel- Fax: 208-772-5970
opment, Joe was responsible for lead design of new E-mail: joehaney@adelphia.net

Brent Kirschner
Business Development Manager
Owen Oil Tools

Brent is currently Business Development Manager at The propellant team values Brents coordination
Owen Oil Tools, and is responsible for the entire efforts as having a central focal point at Owen has
StimGun product line including sales, manufacturing, been a great benefit. In terms of technology develop-
and distribution. Brent serves as Owens primary con- ment, having someone with both a sales perspective
tact for all propellant issues, and is charged with coor- and a chemistry degree has been of great value.
dinating all the various departments, as well as inter- Contact: Brent Kirschner
facing with the other team member companies. Brent Owen Oil Tools
has worked for Owen Oil Tools for seven years in a 8900 Forum Way
variety of positions including sales, planning, and soft- P.O. Box 40666
ware implementation. A member of SPE, ISEE and Ft. Worth, TX 76140
other professional Brent holds a degree in chemistry Phone: 817-551-0540 x129
(B.S. Abilene Christian University, 1982). Brent has Fax: 817-551-0795
about the most diverse experience of anyone in the E-mail: bkirschner@corelab.com
group, with a specialized focus on sales and market-
ing and past experience in construction management.

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John F. Schatz
President
John F. Schatz Research & Consulting, Inc.

Dr. Schatz is principal consultant in the compa- US government. He has a B.S. in physics and a
ny founded to provide his services. Currently, he PhD in geophysics, both from the Massachusetts
provides technical support and custom software Institute of Technology.
(PulsFrac) to the StimGun Group and its Contact: John Schatz
licensees. He also provides consulting services to John F. Schatz Research & Consulting, Inc.
government and industry, primarily in areas relat- 4636 South Lane
ed to rock mechanics. Schatz has 35 years of pro- Del Mar, CA 92014
fessional research and management experience, Phone: 858-792-7410
including directing two commercial rock mechan- Fax: 858-860-2432
ics testing laboratories and developing software E-mail: jschatz@jfsrc.com
for dynamic wave propagation in rocks for the

P. M. (Phil) Snider
Senior Technical Consultant
Marathon Oil Company

Phil Snider is a Senior Technical Consultant for Systems (EXcape Completion Process) now being
Marathon Oil Companys Drilling and Completion utilized in the industry. In support of the propellant
Technology Organization. He provides technical technology, Phil interfaces with licensees, provides
consultation regarding completions to Marathons operator perspective to design of both equipment
engineers, geo-scientists, and management on a and well operations, improves the existing technol-
worldwide basis from their headquarters in ogy portfolio, and coordinates the entire groups
Houston, Texas. He has worked for Marathon in development activities. Phil holds a Petroleum
various capacities for the past 23 years in the Rocky Engineering degree from the University of
Mountain region, Cook Inlet, Alaska, and Gulf of Wyoming (B.S. 1979) and was a 2002 SPE
Mexico. His primary areas of expertise include per- Distinguished Lecturer as well as a past Chair of
foration, explosives, propellants, sand control the API Subcommittee on Perforating and a mem-
strategies, and down hole tool development. Phil ber of the API Subcommittee on Explosives Safety.
holds over 20 patents and has published a similar Contact: Phil Snider
number of technical papers and journal articles Marathon Oil Company
related to oil field completion technology such as P.O. Box 3128
drill stem testing, jet pumping, perforating sys- Houston, TX 77253-3128
tems, and down hole tools. He is one of the inven- Phone: 713-296-3348
tors of the propellant technology (StimGun Fax: 713-296-3397
assembly, StimTube tool) as well as the patent E-mail: pmsnider@marathonoil.com
holder for the Casing Conveyed Perforating

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Other Contributing Authors

R. J. (Ralph) Affinito
Reservoir Engineer
Marathon Oil Company

Ralph Affinito is currently a Reservoir Engineer for Ralph worked five years for Amerada Hess
Marathon Oil Company in Anchorage, Alaska. His Corporation in Williston, ND as a Production and
primary responsibility is reservoir management of Completion Engineer. Ralph holds a B.S. in Petroleum
onshore gas development. He has worked for and Natural Gas Engineering from Penn State. He is a
Marathon for five years as Production, Completion, Licensed Professional Engineer in Wyoming and a
and Reservoir Engineer in Anchorage, Alaska and Member of the Society of Petroleum Engineers.
Cody, Wyoming. Prior to working at Marathon,

James M. Barker
Technology Manager
Jet Research Center, a division of Halliburton Energy Services

James M. Barker is Technology Manager for Jet journal articles associated with electric detonators,
Research Center, a division of Halliburton Energy cement and resin placement using bailers, and perfo-
Services, in Alvarado, Texas. He is responsible for rating in unconsolidated sands. James was an invited
leading the research and development activities of a speaker for several industry forums on topics that
technical staff of 25 people whose work involves oil- included capsule gun perforating, explosive safety,
field explosive devices and down hole perforating and qualification of HPHT explosive systems. James
hardware. special engineering interests include explosive safety,
James has been with Halliburton for 21 years and electric detonators, and the application of rarefaction
has held various engineering management positions shock waves for cutting thick-walled steel structures.
within the company. Prior to his management assign- James holds a Mechanical Engineering degree from
ments, he was a development engineer involved in Texas A&M University (M.S. 1979). He is a member
the design of electromechanical well logging and of the Board of Governors for the Institute of Makers
completion tools, including production logging tools, of Explosives and a member of the API
thru-tubing bridge plugs, perforating hardware, and Subcommittee on Perforating, as well as a past
explosive initiating components. He has received over Industry Advisory Board member for the University of
18 patents related to down hole oil tools and explo- Southwestern Louisiana. He is a registered profession-
sive devices and has co-authored technical papers and al engineer in the state of Texas.

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Craig A. Beveridge
Engineering Technical Advisor
Owen Oil Tools

Craig is currently Engineering Technical Advisor marketing WALS manufactured product to the
for operational aspects of new and existing prod- industry. As a field service engineer for several
uct design for Owen Oil Tools. He updates exist- years, Craig was involved in a wide variety of per-
ing assembly/operations manuals and writes man- forating systems, completion techniques and drill
uals for new products and services and as his stem testing methods. Craig earned a B.S. in
name implies, plans to someday become a home Geology at Muskingum College, New Concord,
brewer. He also prepares and gives technical pre- Ohio (1982) and has participated in numerous
sentations and deals directly with customers on industry related schools. He has been a member
technical issues. Prior to working for Owen Oil of the SPE since 1986.
Tools, Craig served as liaison between the R&D Craigs current efforts related to assisting propel-
department and internal and external customers lant technology development include efforts to
for Western Atlas International, Western Atlas address Nodal Analysis modeling. Craig is charged
Logging Services (WALS). He provided technical with propellant product documentation and oper-
support for the Ballistics product line, both wire- ations manual preparation as well as being able to
line and tubing-conveyed. For two years Craig provide a broad on interfaces with electric line and
was the Global Sales Manager responsible for TCP operations.

David W. Boston
President, Regulatory Affairs Division
Owen Compliance Services, Inc.

David Boston is President, Regulatory Affairs the UN program for these two organizations. He
Division of Owen Oil Tools, where he manages all also represents commercial explosives and ammu-
aspects of regulatory compliance programs, audit nition manufacturers at the UN Committee of
compliance performance, and provides consulting Experts on the Transport of Dangerous Goods.
services for clients including: ATF compliance, David has over 25 years of experience in this
DOT compliance, OSHA compliance, CE compli- aspect of the industry and has managed the proj-
ance. David is a UN consultant to the Institute of ect to obtain proper classification of the StimGun
Makers of Explosives and the Sporting Arms and family of products. He was successful in obtaining
Ammunition Manufacturers Institute. He manages UN class 5.1 classification for these materials.

Kent Folse
Product Champion Tools, Testing & TCP
Halliburton Energy Services

Kent Folse is a Product Champion for optimize perforated completions. He has worked
Halliburton Energy Services Tools, Testing and TCP for Halliburton for 12 years, primarily in the Gulf
product service line based in Carrollton, Texas. He of Mexico region, in operations, sales, and market-
was the product champion within Halliburtons ing capacities. Kent holds a Petroleum Engineering
organization responsible for the commercialization degree from the University of Louisiana-Lafayette
of the StimGun technology. He currently serves as (B.S. 1986) and has authored/co-authored over
the product champion for a project called the four papers on StimGun technology applications.
PerfProSM process that investigates opportunities to

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Paul Gardner
Coordinating Manager Technology
Marathon Oil Company

Paul works as the Coordinating Manager in problems, and understands the need to incorporate
Marathons Technology organization and is currently petrophysical measurements (log, core, special core,
based in Houston, Texas. Marathons Drilling and etc.) and information into seismic evaluation and
Completion Technology group is one of his areas of reservoir delineation and development. Paul has
responsibility. Paul has a Bachelors of Science Degree worked for Marathon in various technical, staff, and
in Geology from Colorado State University and has supervisory positions in Littleton, Colorado;
worked extensively in logging and other aspects of Anchorage, Alaska, and in Houston, Texas impacting
petrophysics. He is familiar with most aspects of open Marathons worldwide projects. The Propellant
and cased hole logging acquisition and interpretation, Technology Development Group values Pauls geolog-
and has worked for Dresser Atlas prior to joining ic, petrophysical, and integrated reservoir description
Marathon. He has worked in several basins around perspective on their activities.
the world with variable lithologies and petrophysical

J. V. (John) Gilbert
Senior Production Engineer
Marathon Oil Company

John Gilbert is a Senior Production Engineer for Marathon, John worked for Schlumberger as a wire-
Marathon Oil Companys Drilling and Completion line engineer for seven years. Performing both open
Technology Organization. He provides technical con- hole and cased hole services as a General Field
sultation on Pressure Transient Analysis and Hydraulic Engineer, John has worked on reservoirs throughout
Fracture Modeling for Marathons engineers on a the world including the Norwegian North Sea, Iran,
worldwide basis from their headquarters in Houston, Vietnam, Yemen and Thailand. John holds a
Texas. He has worked for Marathon for three years Mechanical Engineering Degree from Auckland
after being recruited into Marathons Petroleum University (B.E. 1991) and a Masters of Engineering
Technology Center in Littleton, Colorado then from Colorado School of Mines (M.E. 1999). John
moved to Houston last year. Before joining has published two SPE papers.

Jim Gilliat
Business / Technology Development
Canadian Completions Services The Expro Group

Jim Gilliat works for the Expro Group, based in over a 22-year career and spend 10 very enjoyable
Calgary Alberta Canada in the Business Development years living in Asia. Jims background is first and fore-
Group. His prime responsibility is the commercial most tubing-conveyed perforating but has experi-
development of licensed technologies (StimGun, ence in both electric line and slickline perforating
Pow*rPerf, and EXcape) for Expro. In that capacity applications. Jim has published one SPE paper on
he provides technical support to the sales and field StimGun technology, as well as numerous articles in
operations, customer presentations and computer World Oil, Harts E&P, The JPT, and the Expro
modeling assistance. Jim has held this position for Explorer on perforating technologies and applica-
over 2 years. Prior to joining Expro Jim held a variety tions. Jim is a graduate of the Northern Alberta
of positions, including Product Champion for Institute of Technology (1981) in Petroleum
StimGun with a large multi-national oil field service Resources.
company that allowed him to work in 28 countries

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Perry Huber
Manager-Specialty Services
Plains Perforating Ltd.

The Specialty Services division of Plains Perforating in 1998. Perry has been specializing in
Perforating Ltd is responsible for all technical the interpretation of cased hole and production
aspects of cased hole wire line logging and inter- logs for the past 19 years. Since joining Plains, he
pretation, including propellant stimulation, pro- has also assumed responsibility for the technical
duction logging, cased hole neutron-density logs aspects of propellant stimulations
and cement evaluation. Perry is a graduate of Mechanical Engineering
Perry has over 22 years of industry experience Technology from the Kelsey Institute of Applied
and had been employed with a major integrated Arts and Sciences in Saskatoon, Saskatchewan,
oil company for 18 years before joining Plains Canada (1980).

Kim E. Hungerford
Product Manager Tubing-conveyed Perforating
Halliburton Energy Services

Kim is the Product Manager, tubing-conveyed international locations. In regards to propellants,

Perforating for Halliburton Energy Services. He is he is responsible for the overall coordination
responsible for managing the product life cycle between the Marathon propellant consortium
for hardware, explosives and other technologies and Halliburton. Kim received a B.S. degree in
associated with TCP. He is also the leader of the Petroleum Engineering & Technology (1982)
strategy team for TCP. He has 20 years of experi- from Oklahoma State University in Stillwater, OK.
ence with Halliburton in TCP and has served in a Kim is a member of SPE and has published
number of operational, business development technical articles and co-authored several SPE
and technology positions, in both domestic and papers.

Todd McAleese
Completions Engineer
Marathon Canada Ltd.

Todd McAleese graduated from Montana Techs endorsed the use of high speed recorders to help
Petroleum Engineering program in December improve the effectiveness of the StimGun proce-
2000 and started with Marathon Canada in May dure. Results were so encouraging that a
of 2001. He has worked in the Drilling and 40 well recompletion project (all to be completed
Completions department in Calgary, Alberta as a with StimGun technology) was undertaken.
Junior Completions Engineer since that time. He Prior to attending Montana Tech, Todd graduat-
spent the four months after graduation working ed from the Southern Institute of Technology
with Baker Inteq out of Anchorage, Alaska as an (SAIT) in 1996 with a Petroleum Technologist
MWD engineer. diploma. His work history includes a year working
Todds current duties include cost estimating and for Norcen Energy (now Anadarko) as a
programming completion and workover opera- Production Technologist in their field office in
tions. He has just started a field training program Northern Alberta. Also, there have been three dif-
that will include alternating months in the field. ferent summer intern engineering positions (in
This will hopefully increase his practical knowledge Exploitation and then Drilling and Completions
of completions operations. Todd has programmed with Poco Petroleums now Burlington Canada,
the use of StimGun technology, both wireline and in Production with Marathon Canada) while
conveyed and TCP, in many initial and recomple- obtaining his degree.
tion perforation situations. In particular, he

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Lane Merta
Cased Hole Manager, Lloydminster
Computalog Wireline Services

Lane has been active in the Lloydminster area for experience in case/open hole wireline, Lane has
the last six years. During that time, he has developed actively and successfully promoted propellants and
and modified propellant job procedures, and tool the StimGun assembly for stimulation of heavy oil
configurations to maximize the effectiveness of pro- wells an environment that was thought to be an
pellant stimulation of the wells in this unique shallow undesirable application of propellant stimulation
unconsolidated sand environment. With 26 years of techniques.

Kevin K. Miller
Sr. Production Engineer
Marathon Oil Company

Kevin Miller is located in Midland, TX and is cur- assists other engineers with the application of propel-
rently assigned to the West Texas New Mexico Asset lant for their projects. He also assisted with shaped
Team of the Southern Business Unit. Kevin works charge testing that resulted in the selection of the
with the West Texas water flood properties as an shaped charges that are currently being used through-
operations engineer. He has been with Marathon for out Marathons Southern Business Unit operations.
24 years in various production, operations, and tech- Kevin is Marathons champion of the Baker
nical assignments throughout the company, especial- Atlas/Marathon performance improvement team and
ly in the Permian Basin and in Southern Illinois and is a representative of the Halliburton/Marathon per-
Oklahoma. formance improvement team.
Kevin provided field assistance in the testing and Kevin holds a B.S. in chemical engineering from
development of the current propellant technology and Rose-Hulman Institute of Technology.

Franklin D. Oriold
Area Manager
Canadian Completions Services The Expro Group

Frank is a Registered Engineering Technologist with these various capacities, he has been instrumental in
a Diploma in Petroleum Technology from the the identification and introduction of new technolo-
Southern Alberta Institute of Technology and a gies to the Canadian Oil and Gas service sector
Certificate in Business Development from the including Vanngun tubing-conveyed Perforating,
University of Calgary. Prior to the acquisition of Pow*rPerf Extreme Overbalance Perforating with
Canadian Completion Services by Expro, Frank held Proppant Injection, EXcape Completion System of
positions of President of Canadian Completion Casing Conveyed Perforating and StimGun
Services, President of Canadian Perforators Ltd and Perforating Technologies.
Division Manager Canada Vannsystems/Geovann. In

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Dan W. Pratt
Vice-President, Engineering & Explosives Technology
Owen Oil Tools

He has been with Owen Oil Tools in various and journal articles in the area of perforator per-
capacities since 1984, heavily involved in the formance and design, and formation damage
design and development of new explosives prod- related to perforator/formation interaction. Dan
ucts with emphasis on the perforating shaped has also co-authored papers on charge design pre-
charges and gun systems. His experience and sented at the International Ballistics Symposium.
expertise is in the design of explosive and Dan is an active member of several professional
mechanical products used in the perforation and organizations including SPE, The Society of
stimulation of oil and gas wells and trying to man- Explosives Engineers, and The institute of
age 100 projects at once. Specific expertise is in Explosives Engineers. He has been a member of
Oil Well Perforator / Shaped Charge design, the API Subcommittee on Perforating since 1992.
Perforating System Design, Pyrotechnics and The propellant team values Dans ability to
Explosives, and Quality Assurance. Dan has dual quickly build shaped charges and explosive/pro-
B.S. degrees from the University of Texas at pellant systems to progress the technology. Dans
Arlington, TX with the primary in Mechanical expertise allows new ideas to be fully implement-
Engineering (1980). Dan is the inventor on six US ed and taken to the test sites and utilized within a
patents and several more foreign patents. He has two-week period.
authored/co-authored several technical papers

Craig Smith
Region Manager
TriPoint, Inc. The Expro Group

Craig Smith is region manager for Tripoint, Inc. He designed the first jobs of this type which were
(part of the Expro Group) based out of Oklahoma performed in the Mid-Continent and Northeastern
City, Oklahoma. As region manager, he is current- U.S, and has been involved with the design and
ly responsible for TCP operations, design, and use of propellant in TCP operations since its intro-
sales in the Mid-Continent Region and the north- duction in industry. Craig is also credited with
eastern United States. Craig is also responsible for design and implementation of the first extreme
Tripoints EXcape casing conveyed perforating overbalance StimGun assembly jobs in these
operations, which is based out of this region. areas as well.
Craig holds a Petroleum Engineering Technology Craig has over 25 years of industry experience
Degree from Oklahoma State University (B.S and has previously been employed by Halliburton
1984) and has published SPE papers related to as well.
tubing conveyed extreme overbalance perforating.

Casey J. Weldon
Project Coordinator
Baker Atlas

Casey serves as special projects coordinator for He is the product champion for the propellant
the US land operations of Baker Atlas. With forty technology, (StimGun) which involves customer
years of experience in wireline, tubing-conveyed interface, computer modeling with PulsFrac
perforating, and charge manufacturing, he pro- Software, field training, and technical support.
vides technical support to the field operations in Casey attended McNeese State University, Lake
all of these areas. Charles, Louisiana (1961).

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E. G. (Glynn) Williams, Jr.

Senior Production Engineer
Marathon Oil Company

Glynn Williams is a Senior Production Engineer for He has worked for Marathon for over 24 years. Glynn
Marathons Drilling and Completion Technology has been intimately involved with Gulf of Mexico
Organization. He provides technical consultation for wells for 20 years and with worldwide completions
general drilling and completion operations including for over five years. Glynn holds a Natural Gas
stimulation from their headquarters in Houston, Engineering degree from Texas A&M University-
Texas to Marathons engineers on a worldwide basis. Kingsville (formerly Texas A&I University).

Robert A. (Buddy) Woodroof, Jr.

Technical Manager
ProTechnics, A Core Laboratories Co.
Houston, TX

Buddy Woodroof is Technical Manager for He has served on the SPE Well Completions
ProTechnics based in Houston, Texas; and is currently Committee, Distinguished Lecturer Committee and
responsible for the technical data output products for as a Director and ultimately Chairman of the SPE Gulf
ProTechnics. Buddy also manages the technical com- Coast Section in Houston. He has also served as an
puting center. His department processes all comple- API Technical Subcommittee Chairman.
tion diagnostic logs and prepares reports designed to
The propellant team values Buddys perspective in
aid operators in evaluating and optimizing their com-
terms of proper application of the technology as it
pletions. He joined ProTechnics in 1995 after spend-
ing 23 years with The Western Company/BJ Services relates to well stimulations. Combining the knowl-
in various R&D and technical management positions edge gained from radioactive tracing of fracture stim-
in Ft. Worth and Houston. Buddy obtained a B.S. ulations with the propellant technology for perfora-
degree in Chemistry from the University of Texas at tion breakdown is a key area the team is addressing.
Arlington. He has written numerous technical papers Buddy brings the perspective of the stimulation com-
in the areas of acid corrosion inhibition, well stimula- panies and the operators performing well stimula-
tion, chemical frac tracing and radioactive tracing. tions to the group.

Alphie Wright
Sr. Applications Advisor
Baker Atlas

Alphie is currently a Senior Applications Advisor for Hughes. Alphie has over 17 years of experience cov-
the Completions Group with Baker Atlas. Alphie is ering duties as logging engineer, region engineer,
based in Houston, Texas, and is globally responsible operations manager, district manager, and as techni-
for technical support for ballistics, including both cal support beginning with McCullough, Western
TCP and wireline perforating. He also prepares and Atlas, Baker Oil Tools, and now Baker Atlas. Alphie
presents technical presentations to customers, deals earned a B.S. in Petroleum Engineering at Texas
with technical issues, and is one of the product A&M University, College Station, Texas (1985). He
champions for StimGun and StimTube within Baker has been a member of the SPE since 1982.

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Appendix V: Selected SPE Papers*

SPE 63014: New Techniques for Hydraulic Fracturing in the Hassi Messaoud Field
Diederik van Batenburg, SPE, Halliburtion B.V., Bachir Ben Amor and Rafik Belhaouas, Sonatrach........151

SPE 68101: A Unique Approach to Enhancing Production from Depleted, Highly Laminated
Reservoirs Using a Combined Propellant/Perforating Technique
H. El-Bermawy, SPE, Agiba Petroleum Company and H. El-Assal, Halliburton Energy Services ..............163

SPE 71639: Field Performance of Prepellant/Perforating Technologies to Enhance Placement of

Proppant on High Risk Sand-Control Completions
Kent C. Folse, Richard L. Dupont, and Catherine G. Coast, SPE, Halliburton Energy Services and David B.
Nasse, Shell Offshore, Inc. ....................................................................................................................173

* We would like to acknowledge the Society of Petroleum Engineers (SPE) for their permission to reproduce these papers in their
entirety.

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160 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 161
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162 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 163
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164 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 165
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166 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 167
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168 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 169
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170 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 171
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172 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 173
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174 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 175
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176 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 177
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178 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 179
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180 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 181
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182 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 183
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184 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 185
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186 S t i m G u n T e c h n o l o g y
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S t i m G u n T e c h n o l o g y 187
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188 S t i m G u n T e c h n o l o g y
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