IADC/SPE

IADC/SPE 17237

Lateral Drilling Technology Tested on UCG Project

by P.B. Tracy, Eastman Christensen
SPE Member

Copyright 1988, IADC/i3PE Drilling Conference

This paper was prepared for presentation at the 1988 IADC/SPE Drilling Conference held in Dallas, Texas, February 28-March 2, 1988.

This paper was selected for presentation by an IADC/SPE Program Committee following review of information contained in an abstract submitted by
the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers or International Association of Drill-
ing Contractors and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the IADC or
SPE, its officers, or members. Papers presented at IADC/SPE meetings are subject to publication review by Editorial Committees of th~ IADC ~nd
SPE. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contam conspicu-
ous acknowledgment of where and by whom th!'l paper is presented. Write Publications Manager, SPE, P.O. Box 833836, Richardson, TX 75083-3836.
Telex, 730989 SPEDAL.

ABSTRACT
This case history describes state-of-the-art removal from coal prior to mining start-up and to
lateral drl I I lng technology used to complete an facl I I tate underground gasification In coal
underground system of process wei Is for a UCG deposIts.
project In central Wyoming. The Gas Research Lateral drl I I lng technology
Institute and the u.s. Department of Energy funded Lateral wei Is are categorized by their rate
the project. Eastman Christensen's medium-radius of angle· bul ld, which determines the distance that
system was selected to drl I I the wei Is. must be drll led to turn the wei lbore from Its
The Rocky Mountain 1 Underground Coal vertical or nearly vertical configuration to the
Gasification Project required that six wei Is, horizontal plane. There are three classifications
grouped Into two paral lei modules. be drl I led Into of lateral wei Is: long-radius. medium-radius and
a 30-ft thick coal seam. Vertical depth for the short-radius (Figure 1).
wei Is was approximately 390ft. Each module wl 1 I Long-radius lateral boreholes are drl I led
be used to test a different coal burning process. with conventional directional drl I I lng technology
Key achievements of the drl I I lng phase of the at angle-bul ld rates of 2 to 6 deg/100 ft. The
project Include placing multiple lateral wei !bores wei !bores typically require 3,000-1,000 ft of
In the bottom 3ft of a relatively thin coal seam vertical depth to reach the target zone.
located at shallow vertical depths; running and Medium-radius laterals have bul ld rates of 8
cementing 7-5/8 ln. casing In boreholes with to 50 deg/100 ft, or radl 1 of 700-150 ft, and are
curvatures of 20 deg/100 ft; and completing al 1 drl 1 led using techniques and equipment that are
lateral and vertical wei Is on-target and within logical extensions of conventional directional
stated tolerances. drl I I lng technology. Wei !bores are turned from
the vertical to the horizontal plane In 1,100-200
INTRODUCTION dr I I Ied feet.
Lateral wei Is, commonly cal led dralnholes, Short-radius lateral wei !bores make the
are high-angle holes drl I led radial Jy, usual Jy transition from the vertical to the horizontal
horizontal Jy, from the primary wei lbore Into the plane In 30-60 drl I led feet using unique hardware
pay zone to Increase contact with the reservoir. capable of achieving angle-bul ld rates
Lateral drl I I lng has proved to be a promising of 1.5 to 3 deg/ft with radl I of 20-40 ft.
technology that can enhance ol I recovery and Eastman Christensen's medium-radius system
Improve production efficiency and economics. Its was selected to drl I I the network of process wei Is
major appl !cations are In the ol I and gas Industry for the Rocky Mountain 1 UCG Project for several
where the technology can be used to reach reasons. The system Is steerable In both the
Irregular reservoirs without additional vertical curved and horizontal sections of the hole; and
wei !bores, to I lmlt the Invasion of unwanted the chosen medium-radius bul ld rate of 20 deg/100
formation fluids (coning), to penetrate natural ft allows the use of conventional casing,
vertical fractures and to maximize production of cementing, logging and fishing techniques. Since
low permeabl I Jty and low energy reservoirs by the target depth was less than 400 ft and had an
Increasing the exposure of the formations. angle-bul ld rate of at least 20 deg/100 ft,these
The technology also can be used In the mining features were Important to the success of the
Industry to Increase recovery, efficiency and project.
control In solution mining, to lmpro~..!..__!!!ethane
References and illustrations at end of paper. ________L---------------------------------------------------~
493
2 LATERAL DRILLING TECHNOLOGY TESTED ON UCG PROJECT IADC/SPE 17237

LATERAL DR IlL I NG SYSTEM

UQG protect overy!ew Typically, In a medium-radius completion,
The Rocky Mountain 1 UCG Program was Dlanned casing Is set Immediately above the anticipated
to test ful !-seam gasification of a horizontal kickoff point (KOP), although wei Is with up to
coal seam. The extensive underground system, 8,000 ft of open vertical section have been
designed and Instal led to facl I I tate the drl I led successfully.
gasification process, comprised six wei Is that The zone of Interest frequently Is drl I led
were grouped Into two para! lei modules, as shown through vertically and Jogged In order to
In Figure 2. Approximately 200 tons/day of coal accurately select the horizontal target. Then the
wl 11 be burned over a period of 100 days to test vertical borehole Is either plugged-back to the
two different coal gasification processes. casing point and an oriented departure Is made
The modules are designated by the type of directly off the cement plug or a packer/whipstock
process they wl 11 test. The Extended Linked Wei I assembly Is set In open hole to Initiate the
(ELW) Module Includes two vertical Injection wei Is horizontal section.
and one lateral production wei I. The production Alternately, as was done on this project, the
lateral (PW-1) was to have a 300-ft horizontal kickoff can be made directly off the bottom of the
section In the 30-ft thick coal seam. One vertical hole at a predetermined depth based on
vertical wei !bore (VIW-1) was to Intersect the the known true vertical depth (TVD) of the target
production lateral at Its end point. The second zone.
vertical (VIW-2) was to be drl I led Into the Existing we! Is also can be recompleted with
production lateral 100 ft back toward the oriented laterals Initiated from casing windows or
end-of-curve (EOC). sections. Lateral boreholes can be completed with
The Initial burn In this module wl I I be made standard I lners using Industry-accepted
by Injecting steam and oxygen Into VIW-1. As the technology.
burn cavity Increases In size, the result wl I I be The system uti I !zed to drl I I the underground
Incomplete oxygen consumption. VIW-1 wl I I then be process network Is driven by low-speed,
abandoned and the process wl I I be continued with high-torque, Mach-1 positive displacement downhole
VIW-2 as the Injection wei I. PW-1 wl I I produce motors customized with special combinations of
the combustion products from both gasification stab! I lzers, bent subs and housings, and tl !ted
cavities. drive shafts. A 4-3/4 ln. OD motor drl I Is a 6 ln.
The Control led Retracting Injection Point to 8-1/2 ln. borehole and a 6-3/4 ln. tool drl I Is
(CRIP) Module comprises one lateral Injection an 8-1/2 ln. to 9-7/8 ln. hole. Additional sizes
wei I, one lateral production wei I and one vertical of medium-radius motors are currently under
product Ion we I I. development.
Both lateral we! Is required 300 ft of The 4-3/4 ln. OD motor assembly drl I led the
horizontal hole be placed In the coal seam~ The 6-ln. and 6-1/8 ln. boreholes on the Rocky
production lateral CCPW-1) was to cross over the Mountain 1 UCG Project.
Injection lateral (CIW-1) near or at Its end The system uses two bottomhole motor
point, and the production vertical (CPW-2) was to assembl les to drl I I lateral wei Is: the angle-but ld
Intersect both laterals at the crossover point. CAB) and angle-hold (AH) assembl les. The
The Initial burn In this module wl I I begin at angle-but ld assembly Initiates departure or
the vertical production we! I, CPW-2. Steam and deflects the wei !bore from vertical, and drl I Is
oxygen wl II be Introduced through the CIW-1 the oriented curved section to the final Inc! !n-
lateral with production occurring from CPW-1. ation (Figure 3). The AB assembly drl !Is a curve
When·the BTU value of the product gas drops, at a consistent bul ld rate (I.e., 20 deg/100 ft
successive burns will be Initiated by burning produces a 285-ft radius In a 6-1/8 ln. hole).
through the CRIP liner In CIW-1 at the desired Motor size, borehole size and other considerations
starting point for the next cavity and Igniting a determine the curvature dimensions.
new burn at that point. During the angle-but !ding process, the hole
Each module was designed to have about 300 ft azimuth can be adjusted by control I lng tool face
of open hole for gasification. The relative orientation based on measurement-whl le-drl I I lng
location and Intersection of the process wei Is (MWD) or wire! lne steering tool readings. A
within a module were very Important. Each wei I steering tool monitored hole location and motor
had a specific target or location within the coal orientation during the drl I ling of the six process
seam as well as a location relative to the other we.lls.
process we! Is within the module. To prohibit Penetration rates whl le bul !ding angle with
Interaction between the modules, the lateral the medium-radius system typically are equal to or
production wei Is CPW-1 and CPW-1) were to have greater than those achieved whl le drill lng the
approximately 200 ft between the casing shoes. vertical portion of the wei I.
, AI I wei Is were to be cased and cemented to Following completion of the curved section,
the end of the curve, and then were to be extended either a special angle-hold motor or a rotary
open hole beyond the casing shoe Into the coal angle-hold assembly Is uti I !zed to drl I I ahead
seam. The casing of the production wells CPW-1, through the desired horizon to the target.
CPW-1 and CPW-2) was to be cemented with a The angle-hold assembly most often used, and
high-temperature Fondu cement. The Injection the one uti I !zed on the UCG project, Is a
wei Is (VIW-1, VIW-2 and CIW-1) were to be set with steerable motor system that Incorporates a
Class-G cement containing 30% sll lea flour. customized, double-t I I ted u-jolnt (DTU) housing
Spud-to-release time for the six-wei I program and special stab I I lzers. The assembly permits
was 46 daY$, which compared favorably with the course corrections of 1 to 4 deg/100 ft whl le
45-day estimate. drl I I lng with the motor In a fixed .orientation,
and stralghthole drl I I lng when the bottomhole
assembly Is rotated (Figure 4).

494
IADC/SPE 17237 PATRICK B. TRACY 3

The motor assembly Is slowly rotated from the

surface to maintain the desired Inc I lnatlon and The rig used to drl I I the process wei Is was a
direction and to prevent the bottomhole assembly GardnerDenver truck-mounted unit with pul 1-down
from bul ldlng angle. ·As course corrections are capabl I ltles. It was selected to handle heavy
needed, rotation Is stopped and the toolface Is ol I field tubulars and for ease of rig-up and
oriented to achieve angle deflection In the teardown. The pul 1-down capabl I lty was necessary
desired plane. Once the correction Is made, because weight-adding drl I I col Iars could not be
string rotation Is resumed to drl 11 ahead. The run on the motor assemblies at the shallow depths
combination of motor power and string rotation can being drl I led In the project.
Improve penetration rates. M!.ld.
Standard bit styles most compatible with the The mud system originally specified was a
particular formation being drl I led are used with simple, low-sol Ids, non-dispersed (LSND) fresh
the medium-radius system. water system. The proposed mud weight was less
Compressive serylce ~ ~ than 8.9 lb/gal, viscosity was 30-40 sec/qt and
Medium-radius lateral wei Is with bul ld rates fluid loss was 6-8 cc/30 min.
of 20 deg/100 ft or greater can use special, Whl le drl I I lng the first lateral, stringers
compressive service drl I I pipe (CSDP) that has of swel I lng clays were encount~red, making It
Integral wear knots on the body of the pipe. The difficult to maintain a constant weight-on-bit.
CSDP can be run through t~e curved section and On successive wei Is, a KCI polymer system, made up
below any drl I I col Iars. The col Iars stay In the of a 4% KCI solution and a polymer, was
vertical sect_lon of the hole and supply weight to substituted to the top ot the coal seam. This mud
the assembly. When bul ld rates are less than 20 system adequately cleaned the vertical wei lbore
deg/100 ft, standard heavy-weight drl I I pipe can even up to 65 degrees lncl lnatlon.
be used. When the wei lbore reached the coal seam, the
~ techniques mud was changed back to the LSND system to obtain
Medium-radius lateral drl 11 lng uses better hole-cleaning action In the horizontal
conventional surveying techniques to maintain section. Once the lateral wei Is were finished,
accurate wei lpath direction. the mud system was displaced with 2% KCI water.
In open hole where the casing Is far enough .c.e.m.mt
above the KOP not to be an Interference, or when A qual lty cement job on al 1 the wei Is was
sufficient vertical hole lncl lnatlon allows critical due to the requirements of the coal
"high-side" orientation, an MWD system, gasification process. The cement had to be
conventional wlrel lne steering tool or single-shot capable of withstanding long-term temperature
Instrument Is used for azimuth and/or lncl lnatlon degradation and potential annular gas flow.
contro I. A single joint of 11-3/4 ln., 54 lb J-55
If the kickoff point Is close to or directly pipe, cemented down the backside with ready-mix
out of the casing, a gyroscopic survey Instrument cement, had been\ specified as surface casing for
Is used for the Initial orientation. Thereafter,- the wei Is. Surface casing was· run to 40ft on the
a magnetic survey tool Is used to monitor toolface first wei I, PW-1, and then was decreased to 20 ft
whl le drl I I lng. The survey package for the on successive wei Is.
angle-bul ld assembly Is located about 40 ft above The 7-5/8 ln., 33.7 lb, P-110 casing was to
the bit. be set and cemented to the end-of-curve on lateral
The kickoff point of the laterals drl I led In wei Is and about 2 ft Into the top of the coal on
the UCG project were shallow enough to allow the vertical wei Is. Pipe size was dictated by a wei 1
tools to be Initially oriented from the surface. design that specified 6-1/8 ln. horizontal
sections and a 5-ln. stainless steel CRIP 1 lner.
ROCKY MOUNTAIN 1 UCG PROJECT The 7-5/8 ln. casing In the verticals was
cemented with standard Class-G cement containing
Geology 30% sl I lea flour. A batch-mixed, high-temperature
The Rocky Mountain 1 Project Is located In Fondu cement blend with 40% sl I lea flour was used
the Hanna Formation to the south and sl lghtly west In the laterals. The lateral mixture was dis-
of Hanna, Wyoming. The targeted coal seam Is a placed at 10 bbl/mln. to promote turbulent flow In
zone approximately 30-ft thick with the top at an the annulus.
average true vertical depth of 373 ft. The Rigid stand-off central lzers were used on the
overburden from the surface to the top of the coal first wei I, but were pulled off and replaced with
Is alI sandstone and shale deposited In braided bow-type central lzers because of the resistance
stream, meandering channel and flood plain encountered when the first joint of casing was run
environments. There was the potential, as had Into the curved section of the hole. once a few
occurred In previous characterization wei Is, for ·joints were pushed past the kickoff point, the
some conglomerate zones to washout and cause remaining joints were run In the hole with minimum
caving. effort.
The overburden zones actually drl I led quite A 5-ln. stainless steel CRIP I lner was
wei I. Swel I lng shales were remedied by changing required for the Injection lateral, CIW-1. Each
mud systems and hard stringers, Inconsistent as to joint was welded and thermocouples were attached
depth, caused some rough drl I I lng. Neither as It went Into the hole. The I lner was not
situation affected actual bul ld rates. cemented In place.
The ·ao-.ft coal seam was fairly uniform aJ..1s.
throughout and had a dip of 5-6 degrees to the AI I bits run were soft formation,
east. A uniform, essentially flat coal seam, with ml I led-tooth, roller cone types. The vertical,
few If any anomal les, had been Intentionally curved and horizontal sections were tlme-drl I led
selected for the project. · at approximately 1 min./ft. Bits were typically

495
4 LATERAL DRILLING TECHNOLOGY TESTED ON UCG PROJECT IADC/SPE 17237
replaced during the trips made to change:out Then a survey was run to verify the course
motors or to run surveys; thus most bits showed correction.
only average wear (IADC designations T4, 84 and Dr I I I lng continued with the AB motor assembly
In-gauge) when pulled. to 449ft and another magnetic multlshot survey
.E.L..W ~ was run. Survey data Indicated that a further 90
The Extended Link Wei I (ELW) Module comprises ft were needed to reach the desired angle and
a lateral production wei I (PW-1) and two vertical depth required by the wellplan. The angle-build
Injection wei Is (VIW-1 and VIW-2) that were to assembly drl I led to EOC at 540ft (88 degrees). A
Intersect the production lateral at two different multlshot survey was run. Then the hole was
points (Figure 5). opened to 9-7/8 ln., and 7-5/8 ln. casing was run
fW=1 prodyctlon lateral and cemented at 534ft.
The first wei I drl lied In the ELW module was The angle-hold assembly drl 1 led to 637ft In
the PW-1 production lateral. The vertical well an oriented mode to finish the northern course
locations were dependent on the final location and correction. A multlshot survey was taken, and the
length of the production borehole. AH motor assembly was steered as requlr~d to
Target direction for the PW-1 was due East extend the horizontal section to a TD of 827 ft.
with a tolerance of 10 ft North or south. The fW=1 resy Its
target true vertical depth was 1 ft 9 ln. from the The production lateral was completed wei I
bottom of the coal seam with a tolerance of +or - within given tolerances. The angle-but ld assembly
3ft. The wei !bore could not exit the bottom of performed successful ty, producing average bul ld
the lower carbonaceous shale zone (Figure 6). rates of 22.5 deg/100 ft In the curve and 21.4
The curve was designed for a build rate of 20 deg/100 ft In the coal seam. The hole was brought
deg/100 ft (286-ft radius) using a 6-ln. bit. A back to within 4ft of the original target, wet I
45-degree tangent was planned to make vertical within the given tolerance of 10ft (Table 1).
depth corrections. The EOC was placed In the A 6-1/8 ln. hole size for the curve section
bottom of the coal seam at a TVD of 376 ft and an was recommended for the remaining lateral wei Is as
85.5 degree angle to follow the bottom of the a result of PW-1's higher-than-expected bul ld
dipping coat seam. Hole direction and angle of rates In the soft formations and bit aval lab! I lty.
the wei lbore were to be constantly monitored and YlW=1 ~ YJW=Z lnlectlon verticals
controlled with the steering tool. Target for the VIW-1 was to be within a 3-ft
The vertical and curved sections of the hole radius at the end of the PW-1 production lateral.
were to be opened to 9-7/8 ln., and then 7-5/8 ln. The VIW-2 was to terminate 100 ft back from the
casing run and cemented to EOC. The lateral end, and within 6-ft, of the lateral. The
section of the wei I was to be drl I ted with a 6-1/8 verticals could not exit the bottom of the coal
ln. bit to total depth (TO). Trajectory was to be seam (Figure 7).
control led by orienting the steerable motor as YlW=1 operations
needed to stay within the given tolerances. The 14-3/4 ln. ~urface hole was drl I led, and
fW=1 operations casing was set at 21 ft. A packed bottomhole
A 14-3/4 ln. surf~ce hole was drl 1 ted to a assembly extended the 6-1/8 ln. vertical hole to
measured depth (MD) of 39ft, and 11-3/4 ln. 305 ft. The progress of the borehole was
casing was run and cemented to surface. A 6-1/8 monitored with single-shot surveys. Then at 305
ln. vertical hole was completed to the planned ft,. a magnetic multlshot survey was run to verify
kickoff point of 69 ft. Single-shot surveys were bottomhole location before drl I I lng continued to
used to monitor hole location. the casing point of 374ft. The entire 6-1/8 ln.
The 4-3/4 ln. angle-bul ld assembly, fitted vertical Interval was time-drilled at
with a 6-ln. bit, was surface-oJiented and then approximately 1 mln./ft to minimize deviation of
used to drll I to 101 ft. A magnetic multlshot the wet !bore from vertical.
survey was run to verify kickoff and hole The wei !bore was surveyed again, and a 9-7/8
directions. The curved section was then extended ln. hole-opener was used to enlarge the we I Ibore
with the AB motor assembly to 213ft. Another so that 7-5/8 ln. casing could be run. Then a
multlshot survey was taken. 6-1/8 ln. hole was drl I led Into the coal section
Swel I lng bentonites In this Interval caused to TD.
stabl I lzers to hang up, making It difficult to As the bit approached the PW-1 lateral, a
maintain a constant weight-on-bit. 6-ln. drl I I lng break occurred suggesting that
The angle-hold assembly replaced the Intersection had been achieved. A multlshot
angle-bul ld assembly to drl I I the tangent section survey was run to establIsh the.actual bottomhole
of the curve from 213 to 276ft. Hole tncl lnatlon location of the VIW-1.
was held constant In order to achieve the correct YlW=1 resy Its
vertical drop. Then the AB motor assembly was run Final closure of the bottomhole location was
back In the hole to continue drl I ling the curve. 1.7 ft to the South of the surface location (Table
At this point, It was discovered that the 2).
planned wet I course was ~ East rather than Two time-saving recommendations were made
magnetic East. The bottomhole assembly (BHA) was upon completion· of the VIW-1: (1) succeeding
pulled and the hole was surveyed. It was vertical wei Is would be drl I led with a 9-7/8 ln.
determined that a significant correction was bit to el lmlnate the hole-opening operation; and
required to bring the wei 1 to a ~ East (2) single-shot surveys were demonstrated to b~ as
direction. The wei I path was 25 ft south of accurate as the multlshot surveys and would be·
planned course and direction was 13 degrees off used as the survey of record.
course. YlW=Z operations
The AB motor assembly was tripped In again to A 14-3/4 ln. hole was drl I led to 15ft, and
start the course correction to the North (left) 11-3/4 ln. casing was run and set. Then the
and to continue but ldlng the curve to 404 ft. ·vertical hole was drl I led using a packed-hole·
assembly that Included a 9-7/8 ln. bit and an

496
IADC/SPE 17237· PATRICK B. TRACY 5

8-ln~ non~magnetlc drl I I collar. This Cf.W=.1. production lateral

configuration produced a much stiffer BHA than the The second wei I completed In the CRIP Module
6-1/8 ln. packed-hole assembly previously used and was the CPW-1 production lateral. It was to run 3
drl I led a straighter hole. The 9-7/8 ln. bit ft above the CIW-1, then cross over and TD within
el lmlnated the need for a hole-opener run and the 10 ft of the end of the I lner. Tolerance was+ or.
non-magnetic drl 1 I collar accommodated single-shot -3ft vertically. Based on the results of the
surveys. previous wei I, the curve was designed for a 21.5
Dr I 11 lng continued to a casing point of 364 deg/100 ft bul ld rate with no tangent section.
ft, and casing was set. The wei lbore was End-ofcurve was planned for the bottom of the coal
tlme-drl I led to minimize deviation. A 6-1/8 ln. seam at a TVD of 350 ft, with an angle of 90
hole was then drl I led to a TD of 386ft. As had degrees.
occurred In the VIW-1, the drl I lstrlng dropped CfW=1 operations
6-ln. when the VIW-2 Intersected the lateral The 14-3/4 ln. surface hole was drl I led to
we II bore. 31 ft, and casing was set. A 6-1/8 ln. vertical
YlW=..2. r esu Its hole was completed to a KOP of 80 ft. The
Overal I drl 11 lng time was reduced by more angle-bul ld assemb(y was surface-oriented and then
than two days due to the el lmlnatlon of the used to drl I I the curved section to 102ft. A
hole-opener run and multlshot surveys. Bottomhole multlshot survey was run to verify the kickoff
closure was 0.6 ft, as compared to 1.7 ft on VIW-1 direction.
(Table 3). The multlshot survey showed the hole
.c.B..J.e. M.Q.Q.UJ..E. direction to be sl lghtly North of the target. A
The Control led Retracting Injection Point course correction to the south was started using
(CRIP) Module Included a lateral Injection wei I the AB motor assembly, and then a multlshot survey
(CIW-1), a lateral producllon wei I (CPW-1) and a was run at 173 ft to confirm bottomhole
vertical production wei I (CPW-2) (Figure 8). coordinates. Dr I I I lng continued to a depth of 210
ClW=1 lnlectloh lateral ft, when It was determined that the course
The first wei I drl I led In the Crlp Modu~e was correction could not rectify the wei lpath within
the CIW-1 Injection lateral. Its final location the desired TVD range. A decision was made to
determined the placement of the CPW-1 production plugback and redrl I I the curve.
lateral that had to cross over the top of the A cement plug was set, and the wei I was
Injection borehole. The objectives for the CIW-1 sidetracked at approximately 75 ft. The
were Identical to those of the PW-1 production angle-bul ld assembly drl I led to 375ft. Multlshot
lateral In the ELW Module--- a 300-ft horizontal surveys were taken on 5-ft Intervals at 133 and
length; due East target ~lrectlon with a 10 ft 375ft. The angle-hold assembly was run In the
tolerance North or South and a TVD of 1 ft 9 ln. hole and used to drl I I the tangent section from
from the bottom of the coal seam with a tolerance 375 to 400 ft. Then the AB motor assembly resumed
of +or - 3ft. End-of-curve was planned for a bul ldlng the curve to a casing point of 517 ft,
352-ft TVD at an angle of 89 degrees. and the hole was surveyed with a multlshot tool.
~operations The hole was opened to 9-7/8 ln., and casing
A 14-3/4 ln. surface hole was drl I led, and was run and cemented. The AH motor assembly
casing was set at 27ft. Then a 6-1/8 ln. hole drl I led the casing shoe and then extended the
was completed to the kickoff point at 60ft. The lateral section to 669ft.·
angle-bul ld assembly was surface-oriented and then A multlshot run Indicated that a correction
used to drl I I the curve to a TD of 102ft. A to the South was required to hit the target, which
multlshot survey was run to verify that the hole was a 3ft by 2ft elI Ipse at this point. The AB
was kicked-off In the proper direction. motor assembly drl I led a curve to 714 ft, and
The angle-bul ld assembly drl I led the tangent another multlshot survey was run. These survey
section to a measured depth of 234ft, and then an results were Inconsistent with the Initial
angle-hold assembly was used to extend the section readings, so a third survey was taken with a
from 234 to 267 ft. The AB motor assembly was run different tool. It was ascertained that the
back In the hole and drl I led to a casing TD of 512 Initial survey was faulty and the correction curve
ft. Multlshot surveys were taken on 5-ft stations just completed was unnecessary.
at 234 ft and 512 ft to determine actual bul ld The angle-hold assembly was used to sidetrack
rates and bottomhole location. the wei I at 675ft and then drl I led on to 763 ft.
T~e hole was opened to 9-7/8 ln., and casing T~e hole was surveyed to determine whether any
was run to a TD of 508ft. The AH motor assembly additional corrective measures·were needed. None
drl I led the casing shoe and then completed a 6-1/8 were. The AH assembly extended the production
ln. section to a TO of 814ft. A multlshot survey lateral to a TD of 825 ft, and a final survey was
was taken. .taken.
A stainless steel Injection I lner was run In .c£..W=.1 resu Its
to about 780 ft, 24 ft short of Its proposed The CPW-1 crossed over the CIW-1 lateral at
depth, where It encountered an obstacle. The 2.6 ft and terminated 13 ft from the end of the
target for the production lateral, the CPW-1, was CIW-1's stainless I lner (Table 5). The CPW-1
therefore establ lshed at 780-790 ft (Table 4). crossover lateral establ lshed the location of the
~results CPW-2 Intersecting vertical.
Bul ld rates for the angle-bul ld assembly The angle-bul ld assembly had an average bul ld
averaged 21.6 deg/100 ft above the coal seam and rate of 21.8 deg/100 ft In both the curve and coal
21.1 deg/100 ft Inside lt. The wei !bore was kept sections, and It. successfully drilled the
on-target In the bottom of the coal seam. sidetrack at 75 ft.
The control led rate at which the motor was The angle-hold assembly was steered as needed
bul ldlng angle prompted the decision to complete In the tangent and horizontal sections. It· also
the next horizontal wei 1 without a tangent section drl I led a sidetrack In the horizontal section.
to save time changing out assembl les.
497
6 LATERAL DRILLING TECHNOLOGY TESTED ON UCG PROJECT IADC/SPE 17237
CfW=a production vertical
CPW-2 was a vertical we! I that was to 5. Edlund, P.A.: "Appl lcatlon of Recently
Intersect the crossover of the two laterals, CIW-1 Developed Medium-Curvature Horizontal
and CPW-1. Target tolerance was within 6ft of Drilling Technology In the Spraberry Tr.end
the crossover point. Area,·,;· pa-per SPE/IADC 16170, presented at the
CfW=a operations 1987 SPE/IADC Dr I I I lng Conference, New
A 14-3/4 ln. surface hole was drl I led to 23 Orleans, LA, March 15-18.
ft, and casing was set. The same packed-hole BHA
used on VIW-2 was tripped In and extended the 6. Hyland, C.R.: "Drain Hole Dri I I lng- An old
vertical to 357 ft. The Interval was monitored Idea Whose Time Is Now,"·paper SPE 127~2.
with single-shot surveys. Casing was run and presented at the 1984 Cal ifornla Regional
cemented, and then a 6-1/8 ln. hole was drl 1 led Meeting, Long Beach, CA, Apr I I 11-13.
Into the coal section to a TVD of 377ft.
No drl I I lng break was evident when the 7. Ll, T.K., Chandelle, V. and Brych, J.:
lateral wei Is were Intersected, although drl 11 lng "Lateral Drilling: A New Application Shows
did get very rough Indicating that the edges of Promise," WQr.J.Q. Ql.1 (June 1986), pp. 68-71.
the lateral wei lbores were probably being crossed.
Fluid pumped through the casing on CPW-1 was · 8. Prevedel, B.: "How One Operator Dr I I led
received at the CPW-2 flowl lne. After communica- Hor I zonta I I y Through a Sa It Dome," WQr.J.Q. QJJ_
tion was establ lshed, a final survey was run. (Dec. 1985), pp. 69-76, and 80.
CfW=a resy Its
The CPW-2 Intersected both laterals wei 1 9. Rehm, W.: "Horizontal Dr I I 1 lng Appl led In
within tolerance, and angle was kept to a minimum S I Im HoI es," pet ro Ieym EngIneerIng
with the packed-hole assembly. Maximum International (Feb. 1987), pp. 24-28.
displacement was 0.6 ft due East (Table 6).
10. Stramp, R.L.: "The Use of Horizontal
CONCLUSIONS Dralnholes In Empire Abo Unit, paper SPE
The medium-radius lateral drl I I lng system 9221, presented at the 1980 Annual Meeting,
selected to drl I I the process wei Is on the Rocky Dallas, TX, Sept. 21-24.
Mountain 1 In-situ coal gasification project
achieved the ambitious goals of this project. AI 1 11·. Strelgler, J.H.: "Horizontal Drainhole
wei Is were drl I led within the given tolerances. Dr I I I Ing Update," paper No. B, presented at
The overal I project was completed In 46 days, the 1982 Annual API Production Dept. Meeting,
comparing favorably with a 45-day estimate. The San Antonio, TX, Apr I I 4-7.
results achieved make future work on similar
projects particularly encouraging.

ACKNOWLEDGEMENTS
The author would I Ike to thank the Gas
Research InstItute, the Department of Energy,
Project Conslructlon Corporation and Stearns-Roger
Division of United Engineers and Constructors,
Inc. for their support and permission to pub I Ish
this paper.
REFERENCES

1. Bezalre, G. E. and Marklw, I.A.: "Esso

Resources Horizontal Hole Project at Cold
Lake," paper CIM 79-30-10, presented at the
1979 Annual Meeting of the Petroleum society
of CIM, Banff, Canada, May 8-11.
2. Boslo, J.C., Fincher, R.W., Glannes!nl, J.F.~
and Hatten, J.L.: "Horizontal Dr I I I lng- A
New Production Method," presented at the
12th World Petroleum Congress, Houston, TX,
Apr I I , 1987.
3. Dech, J.A., Hearn, D.O., Schuh, F.J. and
Lenhart, B.: "New Tools AI low Medium-Radius
Hor I zonta I Dr I I I Ing," Ql.1 &. G.a..s. Journa I ( Ju 1 y
14, 1986), pp.95-99.
4. Detmerlng, T.J.: "Update on Drainhole
Dr I I I lng- Empire Abo," Proceedings of 31st
Annual Southwestern Petroleum Short course,
Lubbock, TX (Apr I I, 1984), 25-41.

498
 B 17 23~

PW-1 VIW-1
Survey Summary Survey Summary
Coordinates Coordinates
Point MD Angle Direction TVD North East Elevation Build Rate Point MD Angle Direction TVD North East Elevation

Surface 0.00 0.0 770.3 1591.3 6971.6 Surface 0.00 0.0 766.7 2169.4 6967.5
KOP 69 0.50 S77E 69.0 770.2 1591.6 6902.6 Csg PI 374 0.25 S07W 373.9 765.1 2169.2 6593.6
EOC-1 213 33.50 S70E 204.7 757.0 1631.0 6766.9 22.4 TD 393 0.75 S47E 392.9 764.9. 2169.4 6574.6
EOT 276 33.75 S72E 257.3 745.4 1663.4 6714.3 Target (Based on the PW-11ateral) 392.9 766.2 2168.3 6574.5

EOC-2 540 88.00 NBS E 379.2 732.3 1884.3 6592.4 22.6

(21.4 in coal)
TD 827 83.00 NBOE 397.1 766.2 2168.3 6574.5

Target (Due East) 399.6 770.3 2167.2 6572.0

MD= measured depth TVD =true vertical depth

KOP =kickoff point EOC =end-of-curve EOT =end-of-tangent TD =target depth
Table2

Table 1

VIW-2 CIW-1
Survey Summary Survey Summary
Coordinates Coordinates
Point MD Angle Direction TVD North East Elevation Point MD Angle Direction TVD N-S E-W Elevation Build Rate

Surface 0.00 0.0 750.8 2067.3 6970.0 Surface 0.00 0.0 470.3 1577.8 6973.0

CsgPt 364 0.41 S29W 364.0 750.3 2066.8 6606.0 KOP 60 1.25 N48E 59.9 471.2 1578.2 6913.1

TD 386 0.50 S24W 386.0 750.2 2066.7 6584.0 EOC-1 234 38.25 N89E 221.0 472.1 1635.5 6752.0 21.3

Target (Based on the PW-1 lateral) 385.1 750.4 2067.3 6585.0 EOT 267 38.25 S89 E 247.0 472.2 1656.8 6726.0

EOC-2 512 88.50 S84 E 354.4 460.2 1866.6 6618.6 22.0

(21.1 in coal)
TD 814 84.00 NBBE 361.8 465.9 2167.8 6611.2

Target (Due East) 355.8 470.3 2167.8 6617.2

Table3

Table4

CPW-1 CPW-2
Survey Summary Survey Summary
Coordinates Coordinates
Point MD Angle Direction TVD N-S E-W Elevation Build Rate Point MD Angle Direction TVD N-S E-W Elevation

Surface 0.00 0.0 606.2 1578.9 6970.5 Surface 0.00 0.0 465.4 2146.7 6991.5

KOP 75 0.00 74.9 605.5 1579.3 6895.6 CsgPt 357 0.20 SBOW 357.0 465.4 2147.1 6634.5

EOC-1 375 65.00 S74E 314.1 559.9 1725.7 6656.4 21.5 TD 377 0.25 N14W 377.0 465.4 ·2147.1 6614.5

EOT 400 65.25 S73 E 324.6 553.4 1747.5 6645.9 Target (Based on x-overof CIW-1 and CPW-1) 376.9 465.4 2147.7 6614.6

EOC-2 517 89.75 S78 E 350.2 525.8 1857.2 6620.3 22.2

(21.8 in coal)
X-Over 813 90.75 S79E 354.2 465.4 2147.7 6616.3

TD 825 91.00 sao E 353.9 463.5 2158.8 6616.6

Target (Based on x-over at 10' from liner) 353.8 465.3 2144.0 6616.7

TableS

TableS

499
 LATERAL COMPLETION COMPARISONS

2°-6°/100 It
3000-1000 It radii

~-·.·: .... · ...

1------------2000ft-----------l

f---------1500ft-------_______.,
Pay Zone

Figure 1

Rocky Mountain No. 1 UCG Project

CRIP
Module
0-

100 Coal
u: Seam
.s=
15..
Q)
0 200
(ij
(.)
+=>
~
300

400

0 100 200 300 400 500 600

Horizontal Displacement, Ft

Not To Scale
Figure 2

500
 oJI L.

. ~· .
"'kJ{:

H 17 2 3~

MEDIUM-RADIUS ANGLE BUILDING ASSEMBLY

Build Motor

Low-speed, high-torque motor

~~---Upper bearing housing with

stabilizer

Figure3

Module1
Rocky Mountain No. 1 UCG Project

Plan View

MEDIUM-RADIUS ANGLE HOLDING ASSEMBLY

Hold Motor

100 200 300 400 500 600

Horizontal Displacement, Ft
Low-speed, high-torque motor Double-tilted U-joint housing

Vertical Section

o- PW-1 VIW-2 VIW-1

- 100
LL
~
i5.
Ql
0
~ 200
Figure4
~
~
F
300

100 200 300 400 500 600

Horizontal Displacement, Ft

FigureS

501
 Basic Lateral Wellbore Diagram
Rocky Mountain No. 1 UCG Project

Surface

1w, in. 54# J55 Set At20-40 It

9'/a in. Hole (Pilot Hole Drilled First)

285 It Radius Curve with 15 It Tangent Section

Top of Coal Seam/373 It Average

. ",·.
- 0.
. .. . ...•
• 6Ya in. Open-Hole/300 It Long·
. .

30 It Thick Average

·... ~
• 0

FigureS

Basic Vertical Wellbore Diagram Module2

Rocky Mountain No. 1 UCG Project Rocky Mountain No. 1 UCG Project

Plan View
• CPW-1
14%in. Hole
Surface
··········
······ ·····
100 •••••••••
50
11% in. 47# J55 Set At 15-20 It
·········•···· CPW-2
~C~I~W~-1~---------......_..........·.··~·;·~··~~~
9'/ain. Hole 50

100 200 300 400 500 600

Horizontal Displacement, Ft

Top of Coal Seam/373 It Average Vertical Section

CPW-2
.. ·· ·.
• .',2ft ·• 7% in. 33.7# P-110. I
- .. I
.... ·
0 0 -

..... I
.. :. ·.· . u::
100
I
. •,. ' sf I
i5.
0
Q) I
,' :- : · • · 30 It Thick Coal (Avera.ge) ca 2oo I
., ~ I
~
•• 0

~
I
F 300 I
Lateral Well I
~~~~_[
0 •

100 200 300 400 500 600

'Bottom Of Coal ~eam Horizohtal Displacement, Ft

Figure7 FigureS

502