Advances in

Coalbed Methane

A
A SUPPLEMENT
SUPPLEMENT TO:
TO: SPONSORED BY:
 Coalbed Methane
Advances in
Coalbed Methane Development–A Vital
A supplement to: Part of the Total
Energy Mix
Hart Energy Publications
a division of From hazard to environmental challenge to energy resource – that is
Chemical Week Associates
how the perception of gas contained in coal beds has evolved.

Publisher
RUSSELL LAAS
M ine safety and greenhouse gas
emissions (GHG) and air quality will
for gas instead of oil or coal.
In the United States, where govern-
rlaas@chemweek.com continue to be concerns. But since the ment emphasis is on dramatically
Editor In Chief early 1980s, coalbed gas has increasingly increasing gas supply by the end of this
WILLIAM PIKE been viewed as a valuable energy decade, coalbed gas will play an import-
wpike@chemweek.com resource. Though its contribution to the ant role.
total energy mix is still modest, coalbed
Special Projects Division Editor
MONIQUE A. BARBEE
methane (CBM) has impressive poten- HOW MUCH AND WHERE
tial. It will supplement conventional Though estimates of the total CBM
mbarbee@chemweek.com
natural gas supply, adding another resource vary considerably, they typically
Contributing Editor environment-friendly component to the rise with new understanding and
JOHN KENNEDY total energy mix. technology. But much is still to be
How fast the exploitation of coalbed learned to fully exploit coalbed
Special Projects Art Director gas resources will grow is difficult to methane’s potential.
SHARON G. JOHNSON project; some forecasts made in the mid- In the late 1990s, the U.S. Geological
Production Manager 1990s have proved to be very conserva- Survey (USGS) estimated in-place
JO LYNNE POOL tive. And development will surely coalbed methane resources in the United
accelerate as more is learned about States at more than 700 Tcf; of which
coalbed behavior, and as innovative almost 100 Tcf is economically
Director of Business drilling and completion techniques are recoverable, according to the USGS.
Development applied. Estimates of worldwide CBM
ROY MARKUM On the demand side, coalbed resources are even more difficult to
(713) 993-9325, EXT. 128 methane will be welcome in the market. make, in part because few areas are as
rmarkum@chemweek.com The world’s appetite for gas is expected mature as the United States. Joe Awny,
to grow faster than total energy senior petroleum engineer, Equitable
demand, driven in part by a preference Production Co., said global CBM
President, Hart Publications
RICHARD A. EICHLER
Chief Executive Officer
MICHAEL SILBER
Contents
Hart Publications
4 Understanding Reservoirs, Keeping Costs
Low are Keys to Future
4545 Post Oak Place, Suite 210
Houston, Texas 77027-3105
713-993-9320 9 Stimulation Technology Helps Boost
Main Fax: 713-840-8585 Operators’ Profitability
Editorial Fax: 713-840-0923
Advertising Fax: 713-627-2546
12 A Range of Solutions Available,
More Technology on the Way
 TA P P I N G R E S O U R C E S O U T S I D E
recoverable reserves are about to seven times as much gas as the modest in size and power require-
1,200 Tcf. same volume of rock in a natural ments compared with oil pumping
By comparison, world reserves gas reservoir. The gas content of a equipment, must be capable of
of conventional natural gas are coal bed usually increases with handling water, gas and abrasive
estimated at 5,500 Tcf and U.S. depth and reservoir pressure. The coal fines.
recoverable conventional gas deeper the coal, the less water is Even more daunting – and it
reserves are 183 Tcf.1 contained in the fractures, but may become increasingly
Half of the estimated 100 Tcf of water salinity increases with depth. challenging – is finding a viable
recoverable CBM reserves in the Since water pressure prevents water disposal method that meets
contiguous 48 U.S. states is in the the gas from desorbing, the water or exceeds environmental
Powder River, Northern Appalach- must be removed to reduce the regulations while considering
ian, San Juan and Black Warrior partial pressure in the coal seam so potential future risks for change.
basins. Almost 75 Tcf may yet the gas can be released. After Together, dewatering and
be discovered in the contiguous desorption, the gas spreads produced water disposal costs can
48 states. Another 57 Tcf of CBM throughout the coal bed. often make or break the economic
is estimated to be recoverable Significant coalbed methane viability of a CBM project.
in Alaska.2 production usually occurs only after In the United States, where
In the western sedimentary substantial dewatering. researchers, operators and the
basin of Canada, in-place CBM Coal seam plays can be classified U.S. Environmental Protection

THE
reserves are estimated at more in two major categories. The first Agency are studying possible new
than 400 Tcf in Alberta and 15 Tcf is coalbed methane recovery in requirements for handling
in Saskatchewan. East Coast gas-in- advance of mining operations, produced water in the Powder

U N I T E D S TAT E S
place (GIP) is estimated at 22 Tcf. and the second involves primary River Basin, the sensitivity of CBM
Today, U.S. coalbed methane CBM production in areas too project economics to water
production is more than 4 Bcf/d. deep to mine. In the first mode, handling regulations is shown by
Output totaled only 6 Bcf in 1983, the coal and methane resource are an Advanced Resources Inter-
then jumped to 1,090 Bcf by 1997, recovered in addition to potential national study. It concluded that a
according to the U.S. Energy GHG credits, making gas extraction regulation requiring all water
Information Administration (EIA). economics less critical for project produced from coalbed wells to be
Since then, development has success. The second type of play treated before discharge would
accelerated faster than EIA project- must succeed without mining make 12 Tcf to 15 Tcf of CBM
ed; current annual production of incentives or GHG credits. Like uneconomic in the area.3
more than 1,500 Bcf represents conventional natural gas wells,
more than 7% of annual U.S. coal seam wells are drilled and FINDING COSTS, RECOVERY
gas production. stimulated, but coal’s unique Finding cost, gas recovery and
Key U.S. producing regions physical characteristics call for well productivity also are critical
include the Powder River Basin special techniques. elements in the life cycle economic
with an estimated 24 Tcf of performance of a coalbed
recoverable reserves, the Northern WATER AND ECONOMICS development project.
Appalachian area with 11 Tcf, the Coalbed methane development An early study by the Gas
San Juan Basin with more than 10 has the full range of energy Research Institute (now the Gas
Tcf and the Black Warrior Basin production challenges: technical, Technology Institute) found CBM
with more economic, environmental and finding costs in U.S. basins ranged
than 4 Tcf. regulatory. The solution to many of from U.S. $0.11 to $1.23 per Mcf.
The number of CBM producing these lies in a better understanding Black Warrior and Powder River
wells in the contiguous 48 states of the reservoir and the effective basins reported finding costs of
passed the 15,000 mark in 2001, application of available technology. $0.25/Mcf; in the San Juan basin,
up from 284 wells in 1984. There are several elements to the cost was $0.11.
Australia, with the most the economic challenge. Coalbed methane wells typically
advanced commercial program In the early stages of a project, are on 40-acre to 80-acre spacing,
outside the United States, produces large quantities of water must be but San Juan wells are on 320-acre
about 20 Bcf/year, about 1.3% of pumped from the formation while spacing, according to the study 
U.S. output. little revenue-producing gas is
being recovered. That makes an REFERENCES:
COALBED BASICS early, accurate assessment of the 1. Oil & Gas Journal, Dec. 23, 2002
Because of its large ratio of surface project’s economic potential 2. EandPnet.com
area to volume, coal can store six especially critical. Pumps, while 3. Hart’s E&P, February 2003

C O A L B E D M E T H A N E • MAY 2003 3
Understanding
Reservoirs, Keeping Costs
Low are Keys to Future

Coalbed Methane’s role is modest, even in the few countries with commercial development programs.
But its advantages, particularly in those regions with large coal reserves, are too important to ignore.

I n this article, several leading

coalbed methane (CBM) production
subtle traps, are not issues in
delineating coal reservoirs.
“The global coalbed methane
resource is of some significance in the
experts share their perspectives on “Also, a coal seam is a ‘self- near-term energy mix, where it is
developing this unique resource: sourcing’ reservoir. In a conventional currently being exploited in several
Jonathon Kelafant, vice president, gas reservoir, the source rock is countries including the U.S., Canada,
Advanced Resources International; typically not the reservoir rock, and Australia and China,” he said. “Long
Joe Awny, senior petroleum migration can make definition of the term, the resource is expected to be
engineer, Equitable Production Co.; resource more difficult,” Kelafant said. of great significance for the U.S.,
Andrew Young, regional director, Because coal seams are much India, China, Poland, South Africa,
Australasia for Gaffney-Cline and shallower than most conventional Zimbabwe and elsewhere as a main
current president of the Society of natural gas deposits, drilling and source of gas supply.”
Petroleum Engineers (SPE); Genevieve other costs are lower, he said. In less than a decade, U.S. coalbed
Young, president, H&Y Services; and Predominantly methane, coalbed methane production has jumped to
Karl Schultz, climate protection gas generally requires little processing. about 8% of natural gas consumption.
partnership division, Coalbed Although produced at relatively low “CBM is going to continue to
Methane Outreach Program. rates and low pressures compared play an increasing part in contribut-
“A key advantage of coalbed with conventional natural gas, if ing to the U.S. domestic gas supply,”
methane as an energy source, is its reserves are close to market, it may Andrew Young said. “In countries
low finding and development cost,” not require significant compression. outside the U.S., including my own
Kelafant said. country, Australia, we are seeing
Coal resources are fairly well A GROWING ROLE significant interest and development
defined as a result of coal exploration In some regions, Awny said, coal- of CBM.
and information gained from drilling bed methane could eventually “Because of the major attraction
oil and gas wells, he said. And grow from a supplement to worldwide of gas as a primary energy
challenges that complicate oil and conventional natural gas supply source, the key ingredients for success
gas exploration, such as locating to a main source of gas. in the short-term of methane derived

4 MAY 2003 • C O A L B E D M E T H A N E
 U N D E R S TA N D I N G R E S E R V O I R S
U.S. coalbed methane resource map. (Graphic courtesy of Gas Technology Institute)

from coal seams, is where coal fiscal policy and regulations can be recovered economically,”
resources are coupled with well- play a major role, he said. Genevieve Young said. “Factors
developed gas transportation On the technical side, much of a such as the preserved gas content
infrastructure and gas markets, project’s success depends on well in the coal, the amount of water,
such as the U.S.” and completion designs that will the ability of both water and gas
In the longer term, any country maximize the area of coalbed to flow to a wellbore, the reservoir
with significant coal resources, drawdown to optimize the rate pressure exerted on the coal and
large populations and, hence, high of desorption, Young said. That, the thickness and depth are all
energy demand, offers major in turn, provides the highest produc- significant. For a coalbed reservoir
opportunities for CBM develop- tion rate. A key part of project design to be viable, all of these critical
ment, such as India and China, is optimizing the number, location factors must exist in some unique
he said. and spacing of wells. combination.”
“Another key technical issue is Coal reservoirs are very sensitive
MEETING CHALLENGES the handling and disposal of pro- to drilling and fracture treatment
“The key challenge is to get duced water at as low a cost as fluids, she said. “The coal reservoir
development costs as low as possible and in an environmentally can be easily damaged by stimula-
possible, particularly drilling and sound manner,” he said. tion practices,” Ms. Young said.
completion costs,” Young “It is important to understand “Reservoir characterization is
continued. what controls how methane is essential, but it is not well done
In addition, country-specific trapped in coal and whether it can in coals. It is difficult to obtain well
test results that accurately reflect
reservoir conditions. Reservoir
“A KEY advantage of coalbed methane as an characterization techniques, such
as simulation, are critical to a
energy source is its low finding and better understanding of reservoir
performance, and as an aid in
development cost.” improving operating practices –
— Jonathan Kelafant well spacing in particular.”
Because coalbed methane
Advanced Resources International production requires low-pressure

C O A L B E D M E T H A N E • MAY 2003 5
 Market characteristics vary from
country to country, but most CBM
production will find a ready market.
“In a highly developed market like
the U.S., it is only necessary to get
gas into the distribution system and it
is instantly available to either spot or
medium term contracts,” Andrew
Young said.
In less developed markets, poten-
tial customers must be convinced of
the level of reserves, and producers
require a contract that is sufficient
to stimulate development.
“A different paradigm for con-
tracting CBM gas reserves than that
used for conventional gas reserves
may be needed,” he said. “Further
natural gas reserves are somewhat
easier to estimate in the absence of
Global coal distribution. (Graphic courtesy of Gas Technology Institute) long-term production tests.”

pipeline systems and facilities for otherwise be uneconomic due to GLOBAL OPPORTUNITIES
water disposal, Awny said, the lack of water disposal costs.” “Within the U.S., the Rocky Mountain
an existing infrastructure (from a Improved cased-hole techniques region will continue to be a significant
conventional natural gas play) can would help identify bypassed pay play,” Genevieve Young said.
make initial costs high. zones in existing wellbores. Expansion of CBM’s role in
“In the geologically favorable “And technologies that improve Colorado is an example. Seven years
areas, development is economic at gas-in-place determinations and after coalbed methane volumes
current gas prices. But as drilling identification of natural fractures and became significant enough to report,
expands beyond these areas, the their orientation should continue to its production in the state surpassed
economics are less favorable. Higher be a focus,” she said. that of conventional natural gas in
gas prices or tax credits may be An improved diagnosis of well 1997. By 2000, 53% of Colorado’s
needed to make development completions also is critical to the gas production came from CBM wells.
economic,” he said, summarizing proper application of appropriate “In just the past 5 years, the
the most important needs for fracture fluids. identification of significant natural gas
increased CBM production as: Ms. Young added that to improve reserves in Colorado and the greater
• mapping coalbed methane the success of horizontal wells, two Rocky Mountain region has further
reservoirs; primary technology needs exist: fueled interest in exploration and
• identifying factors that influence improved underbalanced horizontal development,” she said.
reservoir heterogeneity and and multilateral drilling methods During the 1990s, the San Juan
permeability; would help, and a more inexpensive Basin in Colorado and New Mexico
• understanding hydrologic and way to drill horizontal wells – with accounted for the bulk of U.S.
geologic factors that control coiled tubing, for example. coalbed methane production; in the
storage and release of methane “The need for data acquisition late 1990s, Colorado’s greater Rocky
in coal seams; and analysis cannot be over- Mountain region held first place in
• obtaining critical reservoir emphasized,” she said. “With total proved CBM reserves.
parameters that control better data collection, comprehen- But other areas have seen
production; and sive play analysis can help identify more rapid growth. An explosion
• calculating reserves and making and delineate new plays that have of drilling and production in
long-term production forecasts. been overlooked and identify the Wyoming’s Powder River Basin,
“Several advances would accel- larger targets within these areas.” for example, has significantly
erate CBM development,” Ms. Young These regional play analyses increased estimated reserves.
said. “Inexpensive technology to treat should integrate geologic, “The mid-continent and the Gulf
produced water for beneficial surface geophysical and engineering Coast also present potential oppor-
use would make many new coalbed data for accurate resource assess- tunities,” Young said. “Outside the
methane wells attractive that would ment, she said. U.S., application of improved

6 MAY 2003 • C O A L B E D M E T H A N E
 U N D E R S TA N D I N G R E S E R V O I R S
technologies and the development 1990s was important in getting excited by the expanding role of
of adequate infrastructure will be coalbed methane development the professional as we move into
critical to fully exploit some of off the ground. So was about gas-based developments. Gas
these global opportunities.” $65 million in R&D funding pro- creates wonderful opportunities
Operators are active in all U.S. vided by DOE [U.S. Department beyond traditional areas such as
coalbed methane basins, so there is of Energy] and an equal amount fuel for heat and power, including
not likely to be a significant oppor- by the Gas Research Institute,” petrochemicals, fertilizer manu-
tunity that is not currently known. he said. facture, methanol, GTL (gas-to-
Outside the U.S., although CBM “Most of the CBM wells drilled liquid), CNG and DME.”
production is currently almost “too in the U.S. have been drilled since In the drive to develop access
small to measure,” is where the big that incentive expired,” Kelafant to more methane resources,
opportunities lie, Kelafant said. said. “For more than 10 years now, economics and a country’s desire
“I’m very bullish on the potential coalbed methane has competed to be energy self-sufficient will
outside the U.S.,” he said. head-to-head with conventional drive the development of
He estimated the global coalbed natural gas. unconventional gas, including
methane resource at 4,000 Tcf to “There are other issues outside coalbed methane and low
5,000 Tcf, 20% to 25% of which is the U.S., such as ownership, that permeability – tight – gas.
likely to be recoverable. Kelafant are obstacles to rapid development.”
said that for countries with coal “But wherever there is coal, ISSUES REMAIN
reserves, but little conventional oil there is the potential for CBM As understanding of CBM
or gas, such as China, India and development,” Andrew Young said. resources increases and technology
parts of southern Africa, CBM could To determine whether that poten- advances, there are areas in which
offer a gas supply. A five-well pilot tial can be profitably exploited improvement is still needed.
program is underway in South requires an assessment of the coal “The key to addressing those
Africa, he noted. gas capacity and desorption charac- issues is the discovery and appli-
“Some countries may need teristics along with the seam perme- cation of emerging technologies:
incentives, at least to kick-start ability. The depth and level of vari- reservoir simulation, innovative
coalbed development,” Kelafant ability in coalbed characteristics – and geophysical logging techniques and
said. Australia has a research and the economics of development – improvements in stimulation fluids,
development (R&D) tax incentive then become the overriding factors. for example,” Awny said, adding
that applies to coalbed methane. “What is really exciting is the that part of the challenge is that
In other countries, World Bank has possibility for projects that combine mechanical and reservoir properties
funded CBM development efforts, CO2- [carbon dioxide] enhanced cannot be accurately measured in
making available U.S. $10 million recovery of CBM and associated the lab. “Laboratory measurements
each to China and India, with sequestration of this greenhouse fail to duplicate in situ stresses in
$6 million provided to Russia. gas,” he said. The challenge is to coal cleats, joints and natural
“Even though the U.S. does not find locations CO2 can be captured fractures, complicating fracture
need tax breaks now, the Section near a CBM development. simulation,” he said.
29 tax rule that expired in the early “Overall, as SPE president, I am The low reservoir pressure
and low relative gas permeability
found in coal beds require greater
fracture lengths and conductivities
than sandstone reservoirs. Multiple
fractures generated in the coals
during stimulation cause high
treatment pressures and ineffective
stimulation.
Dewatering poses challenges
besides disposal, too.
“The amount of water produced
from coals may not be easily
handled with conventional artificial
lift systems,” Awny said. Produced
water also has scaling tendencies,
and produced CO2 and water is a
corrosive combination.
Coalbed gas production from U.S. lower-48 basins. (graph courtesy of Gas Technology Institute) “Of course, the overarching

C O A L B E D M E T H A N E • MAY 2003 7
 developed from the gas
industry, such as surface
ESTIMATED GLOBAL CBM RESERVES horizontal drilling techniques,
are being applied to expose
more gas to the wellbore and
Location Gas in place, Tcf Estimated recoverable, Tcf reduce the development
U.S. lower 48 states 700 100 footprint. In addition, in-mine
Outside U.S. 4,000 to 5,000 1,200 drainage and boreholes into
the worked out areas of a mine
remain an important part of a
goal is to reduce the cost of develop- additional coalmine and coalbed mine’s methance recovery program.”
ing and producing coalbed methane projects viable. The EPA’s effort to help the
methane,” he said. In the context of greenhouse industry to profitably reduce
Gathering data for decision- gases, reducing methane emissions emissions began in 1989. Mine
making is a particular challenge provides considerable leverage operators were consulted to see
with CBM development projects. compared with reductions in CO2, whether they were interested in
“Sampling, data gathering and for example. Methane is considered putting the gas to market. Feasibility
laboratory testing are all important, to have 21 times the global warming studies assessed drainage efficiency
as is innovation in conventional gas potential of CO2 during a span of and processing for pipelines and
drilling, such as extended reach/ 100 years. Eliminating 1 ton of power generation options.
horizontal wells, multilateral methane has the same impact as “The result was a significant
completions, underbalanced drilling eliminating 21 tons of CO2. increase in the amount of coalmine
and completion practices,” Andrew To help with the effort to reduce gas sent to market, from 14 Bcf in
Young said. “Measurement of CBM coalmine methane emissions, the 1994 to 40 Bcf in 2001,” Schultz
characteristics, such as gas saturation, U.S. Environmental Protection said. The amount of gas now drained
desorption isotherms, gas compo- Agency’s voluntary Coalbed Methane and not used – drained only for
sition, coal density and the associated Outreach Program was established safety – is only about 8 Bcf/year.
variability of the coal seams’ char- to find ways to recover and use The team is looking at alternative
acteristics is critical. Better under- coalmine methane. ways to use the gas, and much of the
standing is also needed of the Karl Schultz leads a team focused emphasis has shifted to ventilation
permeability of the coal seam and on removing gas from coal mines. shaft methane.
the level of free gas in the cleats. The Coalbed Methane Outreach “We are interested in the
“Certification of reserves is Program team is part of the Environ- 90 Bcf/year from ventilation shafts
important. The process is different than mental Protection Agency’s (EPA) in the U.S.,” Schultz said. Globally,
for conventional natural gas in that Climate Protection Partnerships that target is 590 Bcf, representing
production growth is tied closely to Division and partners with the about half the remaining emissions
drilling of development wells. SPE industry to find ways to use gas from coalmines.
definitions remain appropriate, but profitably that otherwise would be “Our ultimate goal is to get at
CBM resources are not well vented. least half of these emissions taken
characterized by just a few wells.” “Coalmine Methane is a subset care of,” he said.
of coalbed methane,” Schultz said. The concentration of gas in the
COALMINE SAFETY CAME FIRST “Our focus is on putting to market ventilation shaft stream is low and
The need that eventually led to the methane associated with coal recovery technology is being
today’s coalbed methane activity is production in underground mines, demonstrated in field-scale tests. One
still an important one – mine safety. rather than the coalbed methane promising technology is flow reversal
Reducing reservoir pressure during that is found in in-mineable seams.” reactors that oxidize methane at a
mining releases methane traditionally In general, the quality of gas from a high temperature, producing heat
vented to the atmosphere, but in mined out area is lower because it is that can dry coal or run turbines.
recent years, mine operators began mixed with air. The objective is to get Financing projects is sometimes
to recover this vented gas. Technical the gas out either in advance of mining difficult. Schultz’s team is looking at
advances, along with changes in the or from areas already mined out to creative financing structures to
utility industry and emission offset safely and efficiently produce coal. facilitate project development.
programs, have motivated mining “Many of the technologies for “Though the U.S. is a leader in the
companies to add methane recovery draining gas in advance of mining are effort, similar coalmine gas recovery
units to ventilation systems. identical to those for more efforts are underway in other countries,
Developing international emissions conventional coalbed development,” including several European countries,
trading markets could help make he said. “Today, technologies China and Australia,” Schultz said. 

8 MAY 2003 • C O A L B E D M E T H A N E
Stimulation Technology Helps
Boost Operators’ Profitability
Halliburton’s specialized technologies can help boost revenue and profit from coalbed methane
projects by minimizing formation damage to increase early production and ultimate recovery.

T he technology also reduces the

cost, time required and footprint of
• high treatment success rate
resulting in reduced financial risk;
equalizing valve that allows tool
movement without overdisplacing
stimulation operations. • the ability to perform treatments the fracturing treatment. The BHA
SM
in large sets to offset lower design enables multiple sets on a
COALSTIM SERVICE output wells; and single trip and a safety shear sub
Applied as a post-frac treatment, • optimize pilot program produc- allows the release of tools.
Halliburton’s CoalStim remediation tion results and minimize
service removes damage because of premature production declines SERVICE HAS HISTORY
fines, gel damage, and geochemical that may negatively impact OF SUCCESS
precipitation and restores production. reserves determination. In Colorado, where a typical well
A decline in initial production or a was 3,500ft (1,067.5m) deep and
departure from an inclined production COBRA FRAC® SERVICE cut up to 20 seams that trap methane,
slope is often a signal that a CoalStim Designed to take advantage of the the multiple seams had plagued
service treatment should be considered. cost effectiveness of coiled tubing, operators. Early on, the most popular
The service process combines a pro- Cobra Frac service can stimulate way to fracture groups of seams
prietary chemical formulation with a multiple zones by straddling each simultaneously had been to use a
field-tested application procedure. individual productive stringer during velocity-over-accuracy approach.
The CoalStim agent acts to solidify a single trip into the well. Cobra Frac But, by the end of 2000, Cobra Frac
the damaging particulates that reduce service teams can often treat multiple service teams were fracturing multiple
the ability to desorb methane and wells in a single day. Single-day seams in a single day.
dewater coal seams. stimulation helps get production on In a highly populated area just
The process has been used widely stream sooner. In addition to speed, outside Liverpool, England, Cobra
in coalbed methane plays in the Uinta Cobra Frac service occupies a smaller Frac service was used to accurately
and San Juan basins. For most coalbed equipment footprint than required for place 3 million lb of sand in five wells;
methane applications, CoalStim conventional fracturing equipment. the increased production brought
service offers several benefits: The Cobra Frac bottomhole significant new revenue.
• helps achieve increased assembly (BHA) is a key factor. In Alabama’s Warrior Basin, Black
incremental production and cash The BHA includes a specially Warrior Methane Co. needed to
flow for a short payout time; designed straddle packer and an stimulate production from three

C O A L B E D M E T H A N E • MAY 2003 9
zones in the J&M Land 8-9-300 well. as is often the case in coalbed Basin were not producing up to
Total thickness of the three methane wells – the improvement potential, each averaging about
formations – the Mary Lee, Blue has been higher. 200 Mcf/d. All three wells were
Creek and Pratt Coal groups – was When fines build geochemical almost identical in depth, hole size
30ft (9.15m) and was distributed precipitates that block paths in the and formation conditions.
over 800ft (244m) of wellbore. Well pack, SandWedge NT can maintain Between 95,000 gal and 100,000
depth was 1,950ft (594.75m), and conductivity by dispersing the effects gal of Delta Frac service 20-lb frac
expected production rate after of fines trapped at the formation/ fluid was used to carry over 300,000
treatment was about 200 Mcf/d. proppant interface. lb of proppant into each well through
After all the coal zones were The system also maintains 51/2-in. casing.
perforated, the fractures were created proppant pack integrity, thus In the well treated only with
in eight stages by isolating 2-ft to stabilizing the filtering mechanics. Delta Frac service, the anticipated
10-ft (0.61-m to 3.05m) intervals. SandWedge also inhibits proppant production increase was achieved.
Using 27/8-in. coiled tubing, each settling in the fracture, providing But production from the two wells
interval was treated with 250 gal of better vertical distribution and treated with Delta Frac with Sand-
28% hydrochloric acid with iron increased propped fracture height. Wedge services almost quadrupled,
control agents. A water-based The result is greater porosity and and the wells still flowed without
60-quality foam system was used to permeability. artificial lift several months after
place 80,000 lb of proppant into the The system helps reduce proppant the job.
Mary Lee and Blue Creek coal groups. flowback by stabilizing the proppant The production increase and lifting
In addition to the Mary Lee and bed. Because the forces between cost savings created an additional
Blue Creek groups, the process broke individual proppant grains and the economic value of more than U.S.
down each set of perforations in the fracture are increased, the proppant $60,000 per month for the operator.
Pratt Group. Coiled tubing fracturing pack can withstand a higher fluid In the San Juan Basin, additional
could not be used in the Pratt Group velocity, allowing more aggressive cavitation had increased production to
since each perforated interval com- cleanup procedures. about 700 Mcf/d from a well that was
municated with open perforations producing from an open hole in the
above. The Pratt Group was stim- DELTA FRAC® CBM SERVICE Basal Fruitland Coal through a cased
ulated by placing 70,000 lb of A high performance fluid system hole in the Upper Fruitland Coal.
proppant down the 51/2-in. casing. designed to stimulate production Halliburton recommended
Instead of the anticipated from coalbed methane wells, the fracturing the Upper Fruitland Coal
200 Mcf/d, the well came in at Delta Frac® CBM service meets U.S. at about 3,000ft (915m), using the
500 Mcf/d against a backpressure Federal Clean Water Act require- SandWedge service as part of a
of 125psi and later was producing ments, an important advantage in 20-lb Delta Frac service treatment.
600 Mcf/d. coalbed methane (CBM) develop- After sand cleanout, production
ment. Requirements for aromatics, began to build almost immediately.
SANDWEDGE® NT such as benzene, have been achieved Within 21/2 months, output was
CONDUCTIVITY ENHANCEMENT without affecting fluid performance. almost 1,200 Mcf/d and no sand
SYSTEM A low polymer borate fracturing had been produced since the initial
In coalbed methane wells, fluid suitable for bottomhole excess was cleaned out.
SandWedge NT enhancer offers the temperatures to 200°F (93.24°C), Total added economic value from
opportunity to achieve several Delta Frac CBM service provides increased production during this
desirable results: several benefits: period was about $132,100.
• increase fracture conductivity; • reduces polymer loading In another San Juan Basin Fruitland
• improve frac fluid cleanup; required to obtain necessary Coal job, water had to be pumped
• reduce proppant flowback; viscosity; off for 6 months before gas sales
• diminish the effects of fines • helps reduce formation damage; could begin, and the well only
migration; and • provides superior retained produced 30 Mcf/d. SandWedge
• improve the permeability of the conductivity; service with a 20-lb Delta Frac service
proppant pack. • provides excellent proppant stimulation treatment was used on a
The SandWedge NT conductivity transport; and new well to enhance conductivity
enhancement system chemically • achieves clean, complete breaks. and help solve the severe sand
modifies the surface of proppant production problems.
grains. Across a range of jobs, SERVICES TOGETHER SHOW After fracturing, the well began
the system has increased production EXCELLENT RESULTS flowing immediately. Sand cleanout
by 20% to 25%; where fines had Three wells in the Fruitland Coal in costs were minimal and pump
a major impact on conductivity – northern New Mexico’s San Juan change costs were eliminated. After

10 MAY 2003 • C O A L B E D M E T H A N E
 S T I M U L AT I O N T E C H N O L O G Y
ADDED ECONOMIC VALUE
SAMPLE RESULTS WITH DELTAFRAC AND SANDWEDGE
Job Production increase Added economic value
Three wells in Fruitland 1.45x-4x $720,000/year
Coal in New Mexico
San Juan Basin 1.7x $132,000 in 2 1/2 months
San Juan Basin 15x $185,000 in first year
Ten wells program in 2.4x $10 million/year
San Juan Basin

being shut in for about 3 months coalbed area indicates it can be program is conducted if justified by
to prepare for production, the well profitably exploited, a structured the economics based on this
began producing at 457 Mcf/d and assessment of the reserve can help estimated production potential.
climbed at a rate of 40 Mcf/d to determine the best development The five-spot program should
50 Mcf/d for some time. approach. include interference testing –
Primarily because of SandWedge In SPE paper 75684, Dana which can yield permeability,
technology, the added economic Weida, Technical Advisor—Reservoir anisotropy and orientation – and
value was about $185,000 in the on Halliburton’s Eastern Business production testing.
first year of production. Development Technical Team, said Data derived from this struc-
Delta Frac Service and this phase of “local asset evalu- tured local assessment program is
SandWedge conductivity ation” should result in a “high- then used as simulator input.
enhancer also helped a major degree of confidence in either
operator add coalbed methane condemning or moving forward on OPTIMIZING THE
production worth an estimated an area. This “structured resource GEOSPATIAL WELL PATTERN
$10 million/year from 10 assessment” should also provide the The best well pattern is one that
coalbed wells in New Mexico’s data necessary to conduct reservoir maximizes the difference between
San Juan Basin. simulations and demonstrate production NPV and capital
Unlike other area operators, production potential. investment, Weida said. Acquiring
who traditionally had drilled Moving from lower-cost to reservoir data and performing
another blind sidetrack wellbore higher-cost, structured evaluation reservoir simulation is the only
that had to be cased and options include: way to determine an economically
cemented, the Delta Frac with • a core hole to obtain full cores optimized well pattern. Geospatial
SandWedge treatments called and geophysical logs; well pattern and completion
for hanging an uncemented liner • a full-size wellbore for open practices determine field-wide
inside the existing 7-in. casing and hole or cased-hole pressure production rates, ultimate
then perforating at four shots per transient testing; recovery and cumulative
foot. The wells that had been com- • a five-spot pilot for interfer- gas production.
pleted open hole were cavitated. ence and production testing. Well pattern refers to spacing
The treatments were pumped Core and log data help and well location. In the United
at a rate of 65 bbl/min using a determine gas-in-place and the States, wells are usually placed on a
20-lb/1,000-gal Delta Frac service potential for water production from north-south and east-west grid
fluid to place 5,000 lb of 20/40 adjacent intervals. Single-test wells, system. But a staggered rectangular
sand/ft of net coal. All proppant used to determine absolute per- pattern aligned with the fracture
was coated using the SandWedge meability, can also be used for a and face cleat can also be effective,
service. fully stimulated production test. Weida said.
Average production from With data from the core hole For a minimal cost, simulation
the under-performing wells and single-test wells, reservoir can provide an economic
increased by 2.4 fold to more simulation, net present value (NPV) assessment, and compare well
than 14.8 MMcf/d. Treatment costs calculations, measured values and a patterns and completion options.
were recovered in 3 months. range of sensitivities provide the Although completion practices
information needed to estimate based on trial and error may be
DEFINING THE RESERVOIR production potential. perceived as a low-cost strategy, it
If evaluation of a prospective A five-spot production test usually is not, Weida said. 

C O A L B E D M E T H A N E • MAY 2003 11
A Range of Solutions Available,
More Technology on the Way
Halliburton has a field-proven package of cost-effective coalbed methane technologies that use special
fluids, equipment and procedures to remove wellbore damage and improve flow through fractures.

A long with fit-for-purpose

equipment that speeds treatments
drilling capability can offer much for
CBM development. The anisotropic
acceptance, especially for degasifi-
cation ahead of mining.
and has a smaller footprint, these cleat permeability in most coals limits Another drilling technology poised
systems can improve financial production from seams with low for expanded application is air coiled-
performance and lower risk. average permeability, though often, tubing drilling. It can cut drilling time
Though much technology is permeability is low in only one by 50% and reduce the footprint on
available today to improve recovery orientation. Efficiently drilled hori- vertical wells. During the next 5 years
of coalbed methane (CBM) and zontals can open these marginal to 10 years, costs could be reduced
reduce development costs, some is permeability plays. 25% to 50% by the development of
under used, often letting an oppor- As the technique gains acceptance area-appropriate equipment.
tunity slip by to enhance project during the next 5 years to 10 years, it Stimulation understanding: The
economics. could boost expected ultimate complexity of CBM fracs exceeds
Emerging technologies span the recovery by 50%. current modeling capabilities.
spectrum from those likely to be Multiple laterals can drain FracTrac® tiltmeter and micro-seismic
developed to “blue sky” ideas. In hundreds of acres from a single mapping, and pressure transient
between are extensions of technology surface location. Industry trials are testing can help optimize treatments
that soon could provide real savings draining 85% of gas in place in in areas still in the initial development
and significant production increases. 1,280 acres from five wells (five-spot phase. Though available, the
With a leading role in CBM well pattern, 300-ft – 91.5-m – spacing) technology is underused. Optimizing
completions and CBM development, in only 2 years. An up-front cost of hydraulic fracture treatment size and
Halliburton has taken a compre- U.S. $2.5 million represents about fluid could yield 20% to 50% greater
hensive look at the impact available $1.50/Mcf. This compares favorably ultimate recovery at a minimal
and emerging technology could have with drilling 32 vertical wells on incremental cost.
on CBM costs and recovery. 40-acre spacing at a cost of Well spacing and geospatial well
$8 million. A central production pattern: Coalbed methane wells
HERE AND NOW facility also reduces operating costs. are typically drilled on 80-acre to
Today’s horizontal and multilateral This concept is set to gain wider 160-acre spacing, often with limited

12 MAY 2003 • C O A L B E D M E T H A N E
 A RANGE
knowledge of the reservoir. Some
wells on excessive spacing have not
seen maximum desorption rates,
even after 8 years of production.
The correct spacing and pattern
allows peak desorption within

OF
1 year to 3 years. Technology is
available to optimize well spacing

SOLUTIONS
using pressure transient and
interference testing, and well
spacing is likely to get more
emphasis as more marginal plays
are pursued. As much as a 100%
increase in net present value could
result from better well placement.
Infill drilling: A recent project
involved infill drilling that reduced
80-acre spacing to 40 acres. New
wells outperformed old ones and
production improved in the old
wells. The operator now has 600
new drilling locations with better Coalbed methane fracture treatment near Durango, Colo.
economics than the original
program. Now cautiously being flow resulting from intermittent see slow implementation.
investigated in major CBM basins, pumping releases migrating coal Nitrogen foam cement: Coal
the infill drilling concept could be a fines. That leads to proppant pack zones usually have normal or sub-
widespread practice within 5 years, plugging, loss of production and normal pressure gradients, which
yielding 75% to 150% increases in- damage to downhole pumps. can allow a significant influx of
field recoveries. Continuously variable pump cement. Nitrogen foam cement has
Continuously variable pump controllers that eliminate the need a density approaching that of water
controllers: As water production to turn pumps on and off could while still providing adequate
decreases during the life of a CBM save one workover every 2 years compressive strength. Ductile
well, intermittent pump operation because of fines influx, and it could foam cement also is resistant to
and changing pump sheaves is possibly boost ultimate recovery by fracturing when perforating.
usually the solution. But the 5% to 10%. Though this tech- Routine use of this technology,
instantaneous changes in water nology is available, it is likely to likely within 5 years, could add
5% to 10% to ultimate recovery.
Coiled tubing frac: Mid-
continent and Eastern U.S. basins
typically have six to 15 producible
coal seams; single-zone stimulation
is usually preferred. Available
systems, such as packer and plug,
ball and baffle, and drillable frac
plugs are cost prohibitive or
inadequate for the large number
of seams.
Coiled tubing systems are ideally
suitable and could begin to have an
impact this year if enough units are
available. The increase in ultimate
recovery could be 15% to 30%.
Enhanced cavitation: Cavitation
is used to enlarge the wellbore and
enhance permeability. Wellbore
enlargement can be promoted with
Halliburton’s Cobra Frac service uses coiled tubing to isolate and stimulate multiple zones. hydraulic jetting. Permeability

C O A L B E D M E T H A N E • MAY 2003 13
 Logging tools for behind-pipe coal
identification would eliminate lost rig
time while logging, perhaps saving
$3,000 per well. Development time is
estimated to be 5 years.

EMERGING TECHNOLOGY
Although technology can reduce
bottomhole flowing pressure to as
low as 30psi to 50psi, as much as
20% to 40% of GIP is not recovered.
Downhole gas compression could
produce the gas left behind, but
10 years may be needed to develop
the technology.
Flue gas sequestration enhances
methane production because of the
preferential adsorption of carbon
dioxide (CO2). The U.S. Department
of Energy is conducting field trials for
smokestack effluent disposal in coal.
In 10 years, enhanced recovery
because of flue gas sequestration
Hydrogen peroxide can remove formation damage and enhance primary production in a variety of well could yield ultimate recovery
and formation types. increases of 20% while providing a
tax credit for disposal.
enhancement resulting from cleat the technology. Other emerging technologies are
realignment during overpressuring Casing drilling with air would aimed at solving water cleanup and
would be accelerated with high rate provide the advantages of air drilling water disposal problems, enhancing
nitrogen injection. The technology is and casing drilling, possibly saving cleat permeability with hydrogen
available to reduce cavitation time by $10,000 per well. The technique also peroxide and developing filtration
4 days to 6 days and increase could be ready in 2 years to 5 years. processes that will clean water to a
production rates by 5% to 15%. Continuous drilling with spooled potable level.
casing (41/2-in. or 51/2-in.) would
EXTENDING TECHNOLOGY increase penetration and eliminate the HYDROGEN PEROXIDE
Downhole water injection pumps are time required to run casing. It could Hydrogen peroxide (H2O2) is a
available, but limited fines tolerance take 3 years to 7 years to develop the powerful oxidizer that can dissolve
hinders their application in coalbed metallurgy and another 5 years to organic polymers and residues.
wells. Better technology is thought to deploy. But cost savings could amount It can remove formation damage
be 10 years to 15 years away. to $10,000 to $20,000 per well. and enhance primary production
Well location size is an issue for Perforations do not give adequate in a wide range of well and
cost and environmental reasons in formation access for stimulation or formation types.
many basins. Small footprint rigs that production in very thin coal seams. Its use has been limited in oil and
can be transported in one or two Cutting slots with hydraulic jets with gas wells because of the lack of an
loads – or a self-propelled unit and a real-time depth control provided by a adequate, safe delivery system for
single additional load – could reduce gamma ray density tool would help. It large volumes capable of pressure
location size and might trim $15,000 could take 10 years to 15 years for injection. Application also was limited
from location cost in rough terrain. technology development and by the lack of process knowledge and
Units could be available now by deployment, but ultimate recovery in poorly understood risk factors.
special order. areas such as Appalachia could A Halliburton team focused on the
By eliminating large mud and flare increase by 20% to 30%. most challenging issue – the catalytic
pits, and blooie lines, closed loop air Sequentially stimulating multiple decomposition reaction with metals,
drilling also could reduce location coal seams with jet slotting and a including steel tubulars and pumping
size, saving $20, 000 to $30,000 coiled tubing deployed bridge plug equipment. Successful development of
per well in mountainous or environ- could cut completion cost by $10,000 their process was driven by the need
mentally sensitive areas. It might on a typical Appalachian well and for a favorable environmental profile
take 2 years to 5 years to develop boost recovery by 20% to 50%. and the ability to handle a wider range

14 MAY 2003 • C O A L B E D M E T H A N E
 A RANGE
• chemical stabilization system:
An additional chemical solu-
tion has a chemical stabilizer
for redundant protection
and integral control, and to
trigger the release of the

OF
peroxide decomposition
reaction where it is needed;

SOLUTIONS
and
• operational process planning
and safety engineering:
Detailed process planning
and engineered controls
includes contingencies to
allow safe and reliable
implementation and field
scale-up of the process.
Last year, a treatment
involving the largest volume of
H2O2 pumped into a producing
well was successfully performed
in La Plata County, Colo., for a
major operator. More than 3,500
Fit-for-purpose hydrogen peroxide delivery system includes a prototype pump unit. bbl of fluid were pumped,
placing 100,000 gal of 3% H2O2.
of applications. mixing in a special tank; The project was part of the field
The resulting process consists of • chemical delivery system: Fit-for- trial phase of a 2-year joint
the following elements: purpose H2O2 delivery system development effort, a planned
• dilution system: On-site, on-the- includes a prototype pump unit six-well pilot study to evaluate
fly H2O2 dilution allows for engineered and built specifically the technical and economic
large volumes to be econ- for H2O2 chemical compatibility merits of H2O2 technology for
omically delivered to location in using cutting-edge composite coalbed methane production
concentrations up to 70% for coil tubing; enhancement. 

POTENTIAL IMPACT OF ADVANCING TECHNOLOGY

Technology Potential
Horizontal and multilateral drilling Increase ultimate recovery by up to 50%
Air coiled-tubing drilling Cut drilling time and cost by up to 50%
Optimizing stimulation Increase ultimate recovery 20% to 50%
Better well spacing Could double NPV
Infill drilling Increase ultimate recovery by 75% to 150%
Continuously variable pump controller Save workovers, boost ultimate recovery by
5% to 10%
Foam cement Increase ultimate recovery by 5% to 10%
Coiled tubing frac Increase ultimate recovery by 15% to 30%
Downhole gas compression Increase ultimate recovery by 20% to 40%
Smaller rigs Save $15,000 per location
Closed loop air drilling Save $20,000 to 30,000/well
Casing drilling Save $10,000/well
Jet slotting Save $10,000/well, increase ultimate
recovery by 20% to 50%
Source: Halliburton

C O A L B E D M E T H A N E • MAY 2003 15