StimGun sect 2 Intro 9/19/02 11:50 PM Page 5

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
Group’s 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 group’s 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.

5
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:50 PM Page 6

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.

6
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:50 PM Page 7

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 Hart’s
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 year’s best new engineer-
and treatment procedures that ensure the cus- ing innovations in the industry’s 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.

7
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:50 PM Page 8

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

8
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 9

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 330°F (160°C). 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 + 1⁄4"/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 + 1⁄2"
(12.7 mm)

Perforating guns – Typically hollow steel carrier guns are recommended. Sleeves are currently available for the follow-
ing gun OD sizes: 23⁄8", 21⁄2", 23⁄4", 27⁄8", 31⁄8", 33⁄8, 4", 41⁄2", 45⁄8", 51⁄8", & 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) = 111⁄16" & 2" (42.9 mm & 50.8 mm). Maximum temperature rate = 255°F (125°C).

9
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 10

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 StimTube’s 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 11⁄2 in., 111⁄16 in., 2 in., 21⁄2 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 – 11⁄2", 111⁄16", 2", 21⁄2", 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 = 340°F (170°C).
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.

10
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 11

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 11⁄2", 111⁄16", 2 in., 21⁄2 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 – 250°F (120°C). 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.

11
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 12

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.”

12
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 13

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 400°F (204°C) 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.

13
S t i m G u n T e c h n o l o g y
StimGun sect 2 Intro 9/19/02 11:51 PM Page 14

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.