Multi-Seam Well Completion 

Technology: Implications for 

Powder River Basin Coalbed

Methane Production

U.S. Department of Energy

Office of Fossil Energy

and

National Energy Technology Laboratory 

Strategic Center for Natural Gas

September 2003

DOE/NETL-2003/1193
Multi-Seam Well Completion Technology: 

Implications for Powder River Basin 

Coalbed Methane Production 

U.S. Department of Energy 

National Energy Technology Laboratory (NETL) 

(Strategic Center for Natural Gas) 

DOE/NETL-2003/1193 

September 2003 
DISCLAIMER 

This report was prepared as an account of work sponsored by an agency of the United 

States Government. Neither the United States Government nor any agency thereof, nor 

any of their employees, makes any warranty, express or implied, or assumes any legal 

liability or responsibility for the accuracy, completeness, or usefulness of any information, 

apparatus, product, or process disclosed, or represents that its use would not infringe 

privately owned rights. Reference therein to any specific commercial product, process, or 

service by trade name, trademark, manufacturer, or otherwise does not necessarily 

constitute or imply its endorsement, recommendation, or favoring by the United States 

Government or any agency thereof. The views and opinions of authors expressed therein 

do not necessarily state or reflect those of the United States Government or any agency 

thereof. 
i

TECHNICAL PREFACE 

Coalbed methane (CBM) production is a substantial component of U.S. domestic 

natural gas supply. The San Juan and Warrior Basins are widely recognized areas of CBM 

development. In the last several years, however, the Powder River Basin has evolved as 

the most active natural gas play in the United States. More than 13,000 wells have been 

drilled in the basin. Moreover, there is the potential for drilling up to 76,000 total wells in 

the basin to fully develop its CBM resources. 

Resource development has primarily occurred along the eastern margin of the basin 

where the coals are relatively shallow and thick, and drilling costs are low. Because of 

these attributes, it is common practice to drill a production well into each seam to drain the 

gas. Generally, thin seams (i.e., less than 20 ft.) are bypassed in favor of developing the 

gas resource in much thicker coals. Completing multiple zones (coal seams) in a single 

wellbore is routine practice throughout industry; however, early attempts at multi-seam 

completions (MSC) in the Powder River Basin have met with mixed and limited success. 

This lack of success and the desire to explore potentially more efficient methods of 

developing CBM in the basin provided the impetus to assess the impacts of MSC. 

The ‘Impacts of MSC’ study is a natural outgrowth of an earlier Department of Energy 

(DOE) analysis of CBM resource development in the Powder River Basin entitled, Powder 

River Basin Coalbed Methane Development and Produced Water Management Study.

Consistent with this initial study, our current analysis was conducted at a township level. As 

with all assessments conducted at such a broad level, readers must recognize and 

understand the limitations and appropriate use of the results. Raw and derived data 

provided in this report will not generally apply to any specific location. Water influx was not 

modeled, although it is acknowledged that this phenomenon may occur in some settings. 

Notwithstanding the drilling of 13,000+ wells, large areas of the basin remain relatively 

undeveloped, which introduces additional uncertainty and increases variability. Proxies and 

analogs were used in the analysis as necessary and appropriate. New data and 

interpretations, which have become available since completion of DOE’s initial evaluation1

have been incorporated into this analysis. Continued development in the basin will 

obviously make additional data and interpretations available, which will lead to a more 
ii

complete description of the coals and their fluid flow properties, and refined estimates of 

natural gas and water production rates and cumulative recoveries. 

As with any resource development evaluation, technical and economic results are the 

product of the assumptions and methodology used. This analysis assumes that MSC 

technology becomes effective and is adopted basin-wide by producers, and permitted by 

states. As such, study results reflect a limiting case (i.e., a maximum benefit) scenario. 

Economic results are before-federal-income-tax (BFIT). It is recognized that natural gas 

prices are volatile and may not be consistent with the price modeled. The price and basis 

differentials modeled however, were representative at the time of study initiation. Users of 

the data, information, and results of this evaluation must consider them wisely within the 

context of their own operations and planning scenarios. Finally, inherent to this analysis, is 

that, along with the increase in CBM production, the additional volumes of produced water 

could be appropriately managed. 

For more information about DOE exploration and production technology projects visit 

the National Energy Technology Laboratory website at www.netl.doe.gov, or the Office of 

Fossil Energy website at www.fe.doe.gov/programs_oilgas.html. Inquiries specific to 

coalbed methane topics should be directed to Peter Lagiovane at: 202-586-8116. 
iii

TABLE OF CONTENTS 

Technical Preface.............................................................................................................i

Executive Summary.........................................................................................................1 

SECTION 1. STUDY PURPOSE, APPROACH, AND FINDINGS ..................................3

1.1 Study Purpose...............................................................................................3

1.2 Current Status of CBM Development.............................................................3

1.3 Study Approach and Methodology...............................................................10

1.4 Summary of Findings...................................................................................15

SECTION 2. STUDY APPROACH AND METHODOLOGY...........................................25

2.1 Basin Area...................................................................................................25

2.2 Basin Structure............................................................................................25

2.3 Basin Stratigraphy .......................................................................................29

2.4 Reservoir Parameters..................................................................................31

2.4.1 Regional Pressure Gradient .................................................................32

2.4.2 Gas Content .........................................................................................32

2.4.3 Gas Saturation......................................................................................34

2.4.4 Coal Fracture and Matrix Porosity ........................................................35

2.4.5 Coal Permeability .................................................................................35

2.4.6 Estimating Gas and Water Production..................................................35

2.5 Multi-Seam Coal Model ...............................................................................36

2.5.1 Coal Inventory ......................................................................................36

2.5.2 Coal Packages and Completion Criteria...............................................38

2.5.3 Volumetric CBM Database ...................................................................41

2.6 Basic Cost Model.........................................................................................42

2.6.1 Capital Costs for PRB CBM Well..........................................................42

2.6.2 Operating & Maintenance Costs for PRB CBM Well ............................45
iv

2.6.3 Gas Transportation, Compression, and Fuel Use ................................45

2.6.4 Other Considerations............................................................................46

2.6.5 Basis Differentials.................................................................................46

2.6.6 Economic Scenarios.............................................................................47

SECTION 3. PERFORMANCE OF MULTI-SEAM CBM WELL COMPLETIONS 

IN THE POWDER RIVER BASIN..................................................................................48

3.1 Background .................................................................................................48

3.2 Overview of CBM Well Completions............................................................48

3.3 Field Case Studies...................................................................................55

3.3.1 Methodology.........................................................................................55

3.3.2 Case Study #1......................................................................................57

3.3.3 Case Study #2......................................................................................64

3.3.4 Case Study #3......................................................................................69

3.3.5 Summary ..............................................................................................71

SECTION 4. APPLICATION AND PERFORMANCE OF MULTI-SEAM 

COMPLETION TECHNOLOGY IN OTHER CBM BASINS............................................73

4.1 Background .................................................................................................73

4.2 Current CBM Development Strategies.........................................................78

4.3 Testing Multi-Seam Well Completion Technology in the Warrior Basin.......79

4.3.1 Background ..........................................................................................79

4.3.2 Multi-Seam Completion Analysis..........................................................80

SECTION 5. BENEFITS OF MULTI-SEAM COMPLETION TECHNOLOGY 

IN THE POWDER RIVER BASIN..................................................................................85

5.1 Summary .....................................................................................................85

5.2 Increased Natural Gas Resources...............................................................85

5.3 Larger Economically Recoverable Resource...............................................89

5.4 Increased State and Federal Revenues ......................................................90
v

5.5 Economic Sensitivity....................................................................................91

5.6 Reduced Environmental Impacts.................................................................92

5.7 Benefits of MSC Technology .......................................................................95

5.8 Detailed Benefits of Using MSC Technology...............................................96

5.8.1 Example #1 ..........................................................................................97

5.8.2 Example #2 ..........................................................................................97

5.8.3 Example #3 ..........................................................................................98

5.8.4 Example #4 ..........................................................................................99

REFERENCES............................................................................................................101

APPENDIX A............................................................................................................... A-1

1. SAN JUAN BASIN.................................................................................................. A-1

2. RATON BASIN ....................................................................................................... A-5

3. UINTA BASIN......................................................................................................... A-8
vi

LIST OF TABLES 

Table 1-1. Multi-Seam Example #1 – Marginally Economic Thick Coal 

Seam is Completed with Thin Seams to Make an 

Economic CBM Well ...........................................................................20

Table 1-2. Royalty and Severance/Ad Valorem Tax Receipts Under Two 

Technology Options ............................................................................21

Table 2-1. Representative PRB Reservoir Properties*............................................31

Table 2-2. Capital Costs for Illustrative CBM Well, Powder River Basin..................43

Table 3-1. Average Case Study #1 Single-Seam Canyon Well and Multi-Seam 

Canyon/Cook/Wall Well, After 12 and 18 Months of Production .........61

Table 3-2. Average Case Study #2 — Single-Seam and Multi-Seam Wells, 

8 Months of Production .......................................................................67

Table 3-3 Average Case Study #3 — Single-Seam and Multi-Seam 

Recompleted Wells ............................................................................70

Table 5-1. Coal and Coalbed Methane Resources of the Powder River Basin, 

by Basin Partition ................................................................................87

Table 5-2. Economically Recoverable CBM by Mineral Ownership.........................89

Table 5-3. State and Federal Revenues From CBM Development in the 

Powder River Basin.............................................................................90

Table 5-4. Economically Recoverable CBM Resources for 

Scenarios #1 and #2 ...........................................................................92

Table 5-5. Number of Wells Required to Produce CBM Resources in 

the PRB, Two Alternative Well Completion Technologies...................95

Table 5-6. Distribution of Economic CBM Resources Under Scenario #1...............96

Table 5-7. Distribution of Economic CBM Resources Under Scenario #2...............96

Table 5-8. Multi-Seam Example #1 – Marginally Economic Thick Coal 

Seam Is Completed with Thin Seams to Make an Economic 

CBM Well............................................................................................97

Table 5-9. Multi-Seam Example #2 – Thin Seams Are Completed with an 

Economic Thick Coal Seam to Increase Well Reserves .....................98

Table 5-10. Multi-Seam Example #3—Multiple Economic Coal Seams Are 

Completed in a Single Well to Reduce Capital Expenditures 

and Surface Disturbance.....................................................................99

Table 5-11. Multi-Seam Example #4 — An Uneconomic Township Is Made 

Economic Using MSC Technology....................................................100
vii

LIST OF FIGURES 

Figure 1-1. Outline and Location of Powder River Basin...........................................5

Figure 1-2. End-of-Year CBM Production Rate for Powder River Basin 

(Wyoming).............................................................................................6

Figure 1-3. End-of-Year Producing CBM Wells for Powder River Basin 

(Wyoming).............................................................................................6

Figure 1-4. Areas of Coalbed Methane Development, Powder River Basin ..............7

Figure 1-5. E-W Cross-Section Showing Splitting of the Thick Wyodak Coal 

Seam into Thinner Units........................................................................9

Figure 1-6. Basin Map Submitted to WYOGCC by CBM Operator in 

Northern PRB, Suggesting Need for Effective Multi-Seam 

Completions........................................................................................12

Figure 1-7. Townships with CBM Well Logs Analyzed for this Report.....................13

Figure 1-8. Gas Content Isotherm Used for Powder River CBM MSC Technology.14

Figure 1-9. Average Synthesized Adsorption Isotherm for Coals in the 

Powder River Basin.............................................................................14

Figure 1-10. Gas-in-Place and Technically Recoverable CBM Resource, 

Powder River Basin.............................................................................17

Figure 1-11. Economically Recoverable CBM Resources using MSC; Two Economic 

Scenarios, Powder River Basin...........................................................18

Figure 1-12. Economically Recoverable CBM Using Multi-Seam (MSC) 

and Single Seam (SS) Technology, Powder River Basin....................19

Figure 1-13. Areas with an Abundance of Thin Seams Requiring 

Multi-Seam Completion Technology for Economic Development, 

Powder River Basin.............................................................................22

Figure 2-1. Coal Basins of Wyoming .......................................................................26

Figure 2-2. Regional Structure and Tectonic Map of the Powder River Basin........27

Figure 2-3. Regional Cross-Section of the Powder River Basin ..............................28

Figure 2-4. Upper Cretaceous and Tertiary Stratigraphic Chart for 

Powder River Basin.............................................................................28

Figure 2-5. Coal-Bearing Units of the Tongue River Member of the 

Fort Union Formation ..........................................................................30

Figure 2-6. Reservoir Pressure Profile Used for PRB Study ...................................33

Figure 2-7. Gas Content Isotherm Used for MSC Study..........................................33

Figure 2-8. Average Synthesized Adsorption Isotherm for Coals in the 

Powder River Basin.............................................................................34

Figure 2-9. Wyodak Coal Seam Time Zero Plot ......................................................37
viii

Figure 2-10. Wyodak Type Well History Match .......................................................38

Figure 2-11. Map Showing Townships from which a CBM Well Log 

Was Analyzed for this Report..............................................................40

Figure 2-12. PRB Coal Database for 24 Townships in Partition #8, 

Northeast Powder River Basin............................................................41

Figure 2-13. Natural Gas and Water Production (as modeled) for One 

Township in Partition #8 Northeast Powder River Basin.....................44

Figure 3-1. Typical CBM Well Completion Practice, Powder River Basin................50

Figure 3-2. Single-Seam Coalbed Methane Well, Powder River Basin ...................50

Figure 3-3. Well Log Showing Typical Fort Union Stratigraphy ...............................51

Figure 3-4. Map Submitted by Powder River Basin Operator(s) Showing 

Areas Where MSC Technology is Vital for Future 

CBM Development..............................................................................53

Figure 3-5. Multi-Seam Completion Option 1 ..........................................................54

Figure 3-6. Multi-Seam Completion Option 2 ..........................................................54

Figure 3-7. Location Map for Multi-Seam Case Studies ..........................................56

Figure 3-8. Location of Yates CBM Wells Included in Case Study #1 .....................58

Figure 3-9. Case Study #1 Single-Seam Well .........................................................59

Figure 3-10. Case Study #1 Multi-Seam Well..........................................................62

Figure 3-11. Time-Zero Production Rate for Average Single-Seam 

Canyon Well and Average Multi-Seam Canyon-Cook-Wall Well ........63

Figure 3-12. Time-Zero Cumulative Production for Average 

Single-Seam Canyon Well and Average Multi-Seam 

Canyon-Cook-Wall Well......................................................................63

Figure 3-13. Time-Zero Water Production Rate for Average 

Single-Seam Canyon Well and Average Multi-Seam 

Canyon-Cook-Wall Well......................................................................64

Figure 3-14. Location of Huber CBM Wells Included in Case Study #2...................65

Figure 3-15. Production Rate for Average Single-Seam Wells (Cook, Wall) 

and Average Multi-Seam Wells (Canyon-Cook-Wall, 

Canyon-Cook-Wall-Pawnee)...............................................................67

Figure 3-16. Cumulative Production for Average Single-Seam Wells 

(Cook, Wall) and Average Multi-Seam Wells (Canyon-Cook-Wall, 

Canyon-Cook-Wall-Pawnee)...............................................................68

Figure 3-17. Water Production Rate for Average Single-Seam Wells 

(Cook, Wall) and Average Multi-Seam Wells (Canyon-Cook-Wall, 

Canyon-Cook-Wall-Pawnee)...............................................................68

Figure 3-18. Location of Majestic CBM Wells Included in Case Study #3 ...............71
ix

Figure 3-19. Average Case Study #3 Canyon CBM Well and its Recompletion......72

Figure 4-1. Location of the Rock Creek Field Research Site, 

Warrior Basin, Alabama ......................................................................74

Figure 4-2. Effect of Multiple Completion of Coal Seams on Breakeven 

Gas Price, Warrior Basin, Alabama.....................................................75

Figure 4-3. Objectives of Multi-Seam Completion Project .......................................76

Figure 4-4. Multiple Completion Potential of Pennsylvanian Age Coals ..................77

Figure 4-5. Percentage Distribution of Abraded Perforation Sets 

within Treatment Intervals, Hendrix Study Area Wells ........................81

Figure 4-6. Downhold Camera Observations at the Soterra 9-7 #1 Well.................82

Figure 4-7. Downhole Camera Observations, Oak Grove #681 Study Well ............84

Figure 5-1. Gas-in-Place and Technically Recoverable CBM Resource, 

Powder River Basin.............................................................................86

Figure 5-2. Powder River Basin CBM Partitions (MSC Study) ................................88

Figure 5-3. Economically Recoverable CBM Resources, Two Economic 

Scenarios, Powder River Basin...........................................................93

Figure 5-4. Impact of MSC Technology on Economically Recoverable 

CBM Resources from the Powder River Basin, Two Scenarios..........94

Figure A-1. Cased Hole Completion, Single-Stage Stimulation, San Juan 

Basin CBM Well ................................................................................A-3

Figure A-2. Open-Hole Completion, Dynamic Cavitation, San Juan Basin 

CBM Well..........................................................................................A-4

Figure A-3. Cased Hole Completion, Multiple-Stage, Small Interval 

Stimulation, Raton Basin CBM Well..................................................A-6

Figure A-4. Cased Hole Completion, Multiple-Stage Large Interval 

Stimulation, Uinta Basin CBM Well ...................................................A-9
1

EXECUTIVE SUMMARY 

The President's National Energy Policy (NEP) Report estimates that over the 

next 20 years annual natural gas consumption in the United States will increase by 

50 percent to nearly 35 trillion cubic feet (Tcf). A contemporary forecast1 fully 

supports this demand increase, though with a short delay. To meet this growing 

demand for natural gas, the NEP report concludes that we will have to fully develop, 

in an environmentally sensitive manner, our nation's economically recoverable 

natural gas resources. 

Natural gas produced from coal seams, commonly referred to as coalbed 

methane (CBM), constitutes 7.5 percent of total annual domestic natural gas 

production, or 1.6 trillion cubic feet in 2001. The Powder River Basin, located in 

northeastern Wyoming and southeastern Montana, is the nation's fastest growing 

source of coalbed methane. At the end of 2002, nearly 1 billion cubic feet of gas per 

day was being produced out of the basin from 10,800 wells. Over the next 10 or 

more years, natural gas development in the Powder River Basin is expected to 

increase dramatically. In the Wyoming portion of the basin, as many as 39,000 

additional wells might be drilled, with the majority of these wells being located on 

federal lands. 

Recognizing the natural gas potential of the basin, as well as the associated 

resource development issues, the U.S. Department of Energy (DOE), Office of 

Fossil Energy, through its National Energy Technology Laboratory, contracted with 

Advanced Resources International, Inc. (ARI) to analyze the basin's geology and 

underlying coalbed methane resources. In a study released in November 2002 

entitled, Powder River Basin Coal Bed Methane Development and Produced Water 

Management Study, DOE determined that the Powder River Basin contains a 

considerably larger quantity of natural gas resources than previously estimated, but 

 

1

 Energy Information Administration. Annual Energy Outlook 2003 with Projections to 2025. 

DOE/EIA-0383(2003). 
2

that development of the basin's coalbed methane resources will be significantly 

impacted by the costs, i.e., economic feasibility, of produced water management 

practices and requirements. 

This study builds on the earlier analysis of the basin.2

 Current results indicate that 

using multi-seam completion (MSC) technology to access the numerous sequences 

of thin coal seams (less than 20 feet thick) would substantial increase the volume of 

recoverable gas and significantly improve the economics of CBM development in the 

basin. 

The technically recoverable coalbed methane resource in the Powder River Basin 

is now estimated to be 50 trillion cubic feet—assuming widespread, successful use 

of MSC technology. Moreover, substituting MSC technology for the currently used 

single-seam well completions would raise the estimate of economically recoverable 

CBM from the basin by 21 Tcf. Significant financial benefits will also accrue to many 

levels of government, as well as to private mineral royalty owners. In fact, state 

severance and ad valorem tax collections are estimated to increase by up to $3.6 

billion, with royalty payments to federal and state governments expected to increase 

by up to $4.1 billion. 

CBM operators in the Powder River Basin have attempted to implement MSC 

techniques that have been developed and utilized in other coalbed methane plays. 

Results to date, however, have generally been disappointing, due to the challenges 

arising from the geologic and reservoir conditions unique to the Powder River 

Basin—shallow, underpresssured, low-rank (low strength) coals surrounded by 

water-bearing aquifers. Clearly, study results provide a basis for further review of 

alternative well completion practices, and a possible technology development/ 

demonstration effort to more efficiently develop the natural gas locked within the 

region’s vast coal resources. 

 

2

 U.S. DOE. Powder River Basin Coalbed Methane Development and Produced Water 

Management Study. DOE/NETL-2003/1184. 
3

SECTION 1. STUDY PURPOSE, APPROACH, AND FINDINGS

1.1 Study Purpose 

The purpose of this study is to evaluate the potential benefits of applying multiseam [well] completion (MSC) technology to the massive stack of low-rank coals in 

the Powder River Basin. As part of this, the study objectives are: 

• Estimate how much additional CBM resource would become accessible and 

technically recoverable — compared to the current practice of drilling one well 

to drain a single coal seam; 

• Determine whether there are economic benefits associated with MSC 

technology utilization (assuming its widespread, successful application) and if 

so, quantify the gains; 

• Briefly examine why past attempts by Powder River Basin CBM operators to 

use MSC technology have been relatively unsuccessful; 

• Provide the underpinnings to a decision whether a MSC technology 

development and/or demonstration effort is warranted by DOE. 

To a great extent, this assessment builds on the previously published study 

(DOE, 2002), which contains many of the key references that underlie this analysis. 

It is available on the U.S. Department of Energy, National Energy technology 

Laboratory, Strategic Center for Natural Gas website (www.netl.doe.gov/scng). It is 

suggested that readers obtain a copy of the original study to complement the current 

report. 

1.2 Current Status of CBM Development 

The Powder River Basin CBM play is located in northeastern Wyoming and 

southeastern Montana (Figure 1-1). Covering 12,000 square miles, the CBM play 

encompasses parts of seven counties in two states, and targets methane contained 

in the tertiary-age Fort Union Formation coal seams. Depths for the play range from 
4

300 feet to over 3,000 feet, and include a series of distinct coal seams, such as the 

Anderson, Wyodak and Big George. 

Although the basin’s potential as a large CBM resource was recognized more 

than two decades ago, its low-rank coals discouraged development. By the mid1990s however, the potential of the Powder River Basin CBM play was better 

understood and activity surged. Over the past five years, development has 

increased dramatically. During 2000, coalbed methane production and the number 

of producing wells more than doubled. Growth in 2001 was nearly as strong. At the 

end of 2002, the CBM play was producing nearly 1 Bcf per day from 10,800 

producing wells (Figures 1-2 and 1-3). 

Within the basin, CBM development is spreading westward, toward the deeper 

basin center from coal outcrops on the eastern edge of the basin. Another focus of 

development is in the Tongue River area on the western side of the basin, along the 

Wyoming-Montana border (Figure 1-4). 

In spite of its large resource potential, numerous barriers exist that may delay or 

even halt the timely development of coalbed methane in the Powder River Basin. 

Recent trends already point to a slowdown in growth for this important domestic 

natural gas play. The reasons for the slowdown are many. Oil and natural gas 

development in the Powder River Basin suffers from inaccessibility to major markets, 

resulting in a high basis differential. In addition, limited outlets and access to hubs 

for this basin lead to relatively high gas-gathering costs. Issuance of permits, 

litigation, and surface use issues also impact resource development efforts in the 

basin. 
5

Figure 1-1. Outline and Location of Powder River Basin. 
6

Figure 1-2. End-of-Year CBM Production Rate for Powder River Basin (Wyoming). 

Figure 1-3. End-of-Year Producing CBM Wells for Powder River Basin (Wyoming). 
7

Figure 1-4. Areas of Coalbed Methane Development, Powder River Basin. 
8

So far, the low costs of drilling the shallow, thick, easy-to-reach coal seams along 

the eastern edge of the basin have been able to offset these economic barriers. 

With the depletion of the geologically more favorable areas, development has moved 

toward the deeper and thinner coals in the central and northern portions of the basin, 

(Figure 1-5). Here, currently used single-seam well completion technology, which 

bypasses the thinner coal seams, may no longer be adequate. 

Management of produced CBM water in the Powder River Basin poses another 

barrier that has been a most visible topic of late. In the arid west, water is a valuable 

resource and, as such, its prudent management is important. Significant volumes of 

water must be pumped from a coal seam to depressurize the coal and allow gas 

desorption to begin. While much of the CBM water in the Powder River meets US 

EPA guidelines for irrigation, stock watering, and even human consumption, some 

areas do not. These areas will have to consider higher cost water management 

options such as reinjection, impoundment, or active treatment. 

These issues, left unaddressed, could limit the development of the Powder River 

Basin CBM play. Economic improvements, such as lower basis differentials and 

gathering costs that would provide a higher netback wellhead price would help, but a 

more comprehensive approach is required. 

One of the most promising means for improving the future outlook for coalbed 

methane in this basin is to develop/adapt alternative well completion technology, 

appropriate for linking multiple coal seams (including thin seams) with a single well. 

Under current practices, a CBM well targets a single thick coal seam (at least 20 feet 

in thickness) and bypasses the thinner seams, because a thinner seam by itself 

simply does not contain enough gas to make an economic well. In areas of the 

basin with thick shallow coals, this completion approach has, for the most part, been 

effective. As CBM development progresses across the remainder of the basin, this 

approach may no longer suffice. However, if several thinner coal seams could be 

completed by a single well, CBM reserves would be significantly increased, while 

adding little to drilling and completion costs. 
9

WASATCH

FT. UNION

WYODAK

ANDERSON

(LOCAL)

CANYON

COOK

(LOCAL)

WALL

U. PAWNEE

L. PAWNEE

CACHE

0 0

15 50

30 100

61 200

122 400

PALEOCENE EOCENE

JAF01915.CDR

FELIX

UCROSS

Meters Feet

Source: Modified from Randall (1989).

WASATCH

FT. UNION

WYODAK

ANDERSON

(LOCAL)

CANYON

COOK

(LOCAL)

WALL

U. PAWNEE

L. PAWNEE

CACHE

0 0

15 50

30 100

61 200

122 400

PALEOCENE EOCENE

JAF01915.CDR

FELIX

UCROSS

Meters Feet

Source: Modified from Randall (1989).

Figure 1-5. E-W Cross-Section Showing Splitting of the Thick 

Wyodak Coal Seam into Thinner Units. 
10

 CBM operators in the Powder River Basin have long recognized the potential 

utility of multi-seam completion technology. Several operators have highlighted 

areas where such technology would be advantageous or vital for further 

development, as shown on Figure 1-6. Unfortunately, because of the unique 

geological and reservoir properties of Powder River Basin coals, the application of 

MSC technology transferred from other CBM basins has been relatively 

unsuccessful. Details of these unsuccessful attempts to produce natural gas 

simultaneously from multiple coals are discussed in more detail in Section 3. 

1.3 Study Approach and Methodology 

To better define the potential of multi-seam well completion technology, and at 

the request of the Department of Energy, Advanced Resources International (ARI) 

undertook the following work to assess coalbed methane resource and technology in 

the Powder River Basin: 

1. Created an up-to-date, township-level database for all coal seams in the 

Powder River Basin. This involved: 

• Analyzing over 270 new well logs from the Powder River Basin (PRB) CBM 

play area (Figure 1-7); 

• Tabulating thin coals with thicknesses of 5 to 10 feet and 10 to 20 feet, by 

depth, stratigraphic interval, and basin area; and 

• Correlating the newly defined thin coal seams with ARI’s existing PRB thick 

greater than 20 feet) coal seams database. 

2. Established packages of multiple coal seams, including thin and thick seams, 

for development by a single well with multi-seam completion technology. 

3. Developed an updated gas content and methane adsorption isotherm specific 

to the Powder River Basin based on more recent gas content and isotherm 

data, as shown in Figure 1-8. For comparison purposes, Figure 1-9 shows 
11

 the range of gas content versus pressure values assembled from past coal 

 samples collected in the PRB. 

1. Applied seam-by-seam coal reservoir properties and history matched “type 

wells” (developed in the previous Powder River Basin study) for: 

• Estimating CBM production and ultimate recovery per well1, and 

• Estimating water production and ultimate recovery per well1

. 

Collected detailed cost data on multi-seam well completions from vendors and 

producers, incorporated these data to update ARI’s existing Powder River cost 

model, and employed ARI’s economic model as follows: 

• Used a long-term $3.50/Mcf (flat) price track at the Henry Hub, 

• Included costs of applying MSC technology for completing up to four coal 

zones per well, consistent with practices in other CBM basins, 

• Modified certain water management infrastructure costs, and 

• Used two distinct basis differential cases. 

1. Estimates include areas already under development. 
12

Figure 1-6. Basin Map Submitted to WYOGCC by CBM Operator in Northern PRB, 

Suggesting Need for Effective Multi-Seam Completions. 

Few logs exist in Montana and the western edge of the play. 
13

Figure 1-7. Townships with CBM Well Logs Analyzed for this Report. 
14

Figure 1-8. Gas Content Isotherm Used for Powder River CBM MSC Technology. 

Figure 1-9. Average Synthesized Adsorption Isotherm for Coals in the Powder 

River Basin. 

0

20

40

60

80

100

0 100 200 300 400 500

Pressure (psia)

Gas Content (scf/ton)

0.0

0.8

1.7

2.5

3.4

4.2

Gas Content (scf/cf)

0

20

40

60

80

100

0 100 200 300 400 500

Pressure (psia)

Gas Content (scf/ton)

0.0

0.8

1.7

2.5

3.4

4.2

Gas Content (scf/cf)

Source: From Wyoming EIS support documents, 2002. Average synthesized adsorption isotherm for 41 coal samples 

from the PRB, based on a compilation of data from public and private sources. Gas Content (scf/ton)

Pressure (psia)

0

40

60

80

0 100 200 300

20

400 500

Avg scf/t

+1 std dev

-1 std dev

JAF02188.PPT

Source: From Wyoming EIS support documents, 2002. Average synthesized adsorption isotherm for 41 coal samples 

from the PRB, based on a compilation of data from public and private sources. Gas Content (scf/ton)

Pressure (psia)

0

40

60

80

0 100 200 300

20

400 500

Avg scf/t

+1 std dev

-1 std dev

JAF02188.PPT
15

Canvassed operators and assembled well completion and production records on 

the use and performance of MSC technology in the basin, as further discussed in 

Section 3. This helped to identify problems with current technology, to compare 

multi-seam performance with single-seam technology performance (in a similar 

geologic setting), and to examine why simple transfer of multi-seam technology from 

other CBM basins has not worked in the Powder River Basin. 

For a more comprehensive discussion of the reservoir characterization, 

production analysis, and cost model for the Powder River Basin, readers are 

directed to DOE’s previously referenced (produced water management) study. 

1.4 Summary of Findings 

The Powder River Basin has numerous sequences of thin coal seams that 

extend over major areas of the basin, particularly along the northern portion of the 

basin, and in Montana. The inclusion of these thin (less than 20 feet of thickness) 

coals and their production using MSC technology significantly increases the 

accessible technically CBM recoverable resource in this basin. Even more 

important, the economics of CBM development in the Powder River Basin can be 

improved, assuming the adaptation and successful application of MSC technology. 

The current outlook for coalbed methane in the Powder River Basin and the role 

of MSC technology are summarized below: 

1. The gas in-place in the Powder River Basin, including both thick coals and thin 

coals seams, is estimated at 75 Tcf. MSC technology enables a producer to link 

currently bypassed coal to a production well. This would provides access to a 

significantly larger portion of the CBM resource in the Powder River Basin than 

can be achieved with currently used single-seam well completion practices. 

Figure 1-10 shows the study’s estimate of CBM gas in-place in the Montana 

(MT) and Wyoming (WY) portions of the Powder River Basin. 

2. The technically recoverable coalbed methane resource in the Powder River 

Basin - assuming successful use of MSC technology - is estimated at 50 Tcf. 
16

MSC technology enables the CBM resource in thin coals to be co-produced with 

traditionally produced thick coals, significantly increasing the technically 

recoverable CBM resource in the basin. Figure 1-10 shows the technically 

recoverable CBM resource in the Montana and Wyoming portions of the Powder 

River Basin. 

3. The economically recoverable coalbed methane resource is estimated to range 

from 24 to 38 Tcf. This estimate assumes a natural gas price of $3.50/Mcf at the 

Henry Hub and two different outlooks for the basis differential between the Henry 

Hub and the Colorado Interstate Gas (CIG) Hub. 

 Because of limited pipeline capacity and access to markets, the wellhead gas 

price in the Powder River Basin has, at times, been severely depressed. Basis 

differentials between the Henry Hub and the CIG Hub have increased from a 

historical average of $0.80/Mcf to about $1.80/Mcf. Under the first scenario 

examined by the study, a scenario where increasing natural gas production 

volumes from the PRB and other Rocky Mountain basins continue to exceed 

pipeline take-away capacity, the relatively high basis differential of $1.80/Mcf 

remains. Under the second scenario examined in this study, sufficient new 

pipeline capacity is built to return the basin differential, over time, to a more 

historic norm of about $0.80/Mcf. 

 Figure 1-11 shows the economically recoverable CBM resource in the Powder 

River Basin for these two basis differential scenarios. Under the scenario (#1) 

where basis differentials remain at current levels, economically recoverable CBM 

is reduced by 14 Tcf, and the Montana portion of the PRB CBM play becomes 

uneconomic to further develop. 

4. Application of successful MSC technology to the Powder River Basin CBM play 

would add 20-plus Tcf of economically recoverable resource. Widespread, 

successful application of MSC technology for continued use of single-seam well 

completion technology would significantly increase the portion of the CBM 

resource that becomes economically viable. [This impact (benefit) of MSC 
17

technology is examined using a $3.50/Mcf (Henry Hub) natural gas price and the 

recent practice of using impoundments or shallow reinjection (in select areas of 

the basin) for produced CBM water management.] 

 As shown on Figure 1-12, under Scenario #1, the continuation of today’s high 

basis differentials, successful use of MSC technology would increase 

economically recoverable resources by 21 Tcf over continued use of singleseam technology. Under Scenario #2 (represents a return to a historical basis 

differential of $0.80/Mcf), successful use of MSC technology would increase 

economically recoverable resources again, by 21 Tcf over continued use of 

today’s single-seam technology. 

Figure 1-10. Gas-in-Place and Technically Recoverable CBM Resource, 

Powder River Basin. 

44.2

68.7

5.9

5.3

0

10

20

30

40

50

60

70

80

Tcf

Wyoming Montana

Coalbed Methane

Gas-in-Place

Technically 

Recoverable

Resource

74.6

49.5

44.2

68.7

5.9

5.3

0

10

20

30

40

50

60

70

80

Tcf

Wyoming Montana

Coalbed Methane

Gas-in-Place

Technically 

Recoverable

Resource

74.6

49.5
18

Figure 1-11. Economically Recoverable CBM Resources using MSC; 

Two Economic Scenarios, Powder River Basin. 

5. Successful MSC technology would beneficially impact CBM development in the 

Powder River Basin in many ways, as illustrated by the following examples: 

• In Example #1, currently uneconomic, marginally thick coals are completed, 

along with a series of thin coals to make an economic well (discussed further 

below). 

• In Example #2, several thin coal seams that are bypassed under present 

practices are completed, along with a currently economic seam to increase 

reserves per well, while adding relatively little to costs beyond additional 

perforations/stimulation, a larger water lifting capacity and some increased 

operating and maintenance costs. 

24.3

0

5

10

15

20

25

30

35

40

45

Tcf

Wyoming Montana

Figure 1-11. Economically Recoverable CBM Resources;

Economic Resource

(declining “basis differential”)

Economic Resource

(flat “basis differential”)

37.1

1.3

38.4

24.3

Scenario #1 Scenario #2

24.3

0

5

10

15

20

25

30

35

40

45

Tcf

Wyoming Montana

Figure 1-11. Economically Recoverable CBM Resources;

Economic Resource

(declining “basis differential”)

Economic Resource

(flat “basis differential”)

37.1

1.3

38.4

24.3

Scenario #1 Scenario #2
19

Figure 1-12. Economically Recoverable CBM Using Multi-Seam (MSC) 

and Single Seam (SS) Technology, Powder River Basin. 

• In Example #3, two (or more) economic seams are completed within the 

same well to reduce capital expenditures while cutting the required number of 

CBM wells in half (or less). 

• In Example #4, a basin area containing only thin coals is made economic by 

completing up to four seams in one well. This case is of particular 

importance in the northern portions of the play where thick (>20 ft.) coals are 

much less common. Without MSC technology such areas can be expected 

to remain undeveloped. 

These four examples cover many of the geologic settings encountered in the 

PRB, including the central portion of the basin where thin seams coexist with major 

thick coals, as well as the northern and western basin flanks where much of the coal 
20

is deposited only in thin seams. Further examination of these four examples is 

provided in Section 5.8. 

6. MSC technology has the potential for converting uneconomic, marginally thick 

seams and by-passed thin seams into economic reserves. In this elaboration of 

Example #1, a single seam CBM well targeting the 25 ft. Canyon coal seam in 

T54N R80W is expected to recover 0.21 Bcf of gas. With this low gas recovery, 

the well is sub-economic. With MSC technology, the Canyon coal seam in this 

township can be completed with three additional thin seams (16 ft., 19 ft., and 

15 ft.) that would have been bypassed under current practices. The result is an 

economic CBM well that is expected to recover 0.57 Bcf. In addition, the 

packaging of four coal seams in one well significantly lowers finding and 

development (F&D) costs in this township from an uneconomic $0.67/Mcf to an 

economic $0.27/Mcf. 

 The benefits of applying MSC technology in Example #1 are summarized in 

Table 1-1 below: 

Table 1-1. Multi-Seam Example #1 – Marginally Economic Thick Coal Seam is 

Completed with Thin Seams to Make an Economic CBM Well 

Current Single-Seam 

Technology 

Proposed Multi-Seam 

Technology 

CAPEX/Well $139,950 $154,960 

EUR/Well 208 Mcf 566 MMcf 

F&D Cost $0.67 per Mcf $0.27 per Mcf 

Additional detail on capital expenditure (CAPEX) costs is provided in Section 2.6. 

7. Widespread use of MSC technology would significantly increase Montana, 

Wyoming, and Federal revenues. Another benefit of successful use of MSC 

technology would be increased royalty, severance, and ad valorem payments to 

state and federal governments. Under Scenario #2, with an economic resource 

base of 38.4 Tcf, royalty payments to local, state, and federal budgets from 

application of MSC technology would be $6.4 billion, an increase of $3.6 billion 
21

over royalty revenues that would be generated from continued use of current 

well completion practices. $7.4 billion in severance and ad valorem taxes ($0.2 

billion for MT; $7.2 billion for WY) would be generated from successful 

application of MSC technology. This is an increase of $4.1 billion ($0.2 billion 

for MT; $3.9 billion for WY) over severance and ad valorem taxes that would be 

generated from continued use of current completion practices. 

 Table 1-2 provides a summary of these revenue benefits for Montana, 

Wyoming, and the federal budget; using the royalty and severance tax 

information in the economic model discussed in Section 2.6. 

Table 1-2. Royalty and Severance/Ad Valorem Tax Receipts Under 

Two Technology Options. 

With MSC 

Technology 

With Single Seam 

Technology Benefit of MSC Technology 

Revenue 

Sources MT WY Federal MT WY Federal MT WY Federal 

Royalties 

(millions of $) $30 $819 $5,536 - $373 $2,433 $30 $446 $3,103 

Severance/ Ad 

Valorem Taxes 

(millions of $) $203 $7,197 - - $3,278 - $203 $3,919 - 
22

Figure 1-13. Areas with an Abundance of Thin Seams Requiring Multi-Seam 

Completion Technology for Economic Development, Powder River Basin. 

8. Multi-Seam technology is essential for developing the CBM resource in Montana 

and on Indian lands, areas that contain an abundance of CBM resource in thin 

coal seams. The CBM play in Montana and the northern Wyoming portion of the 

Powder River Basin has the bulk of its resource in thin (< 20 ft.) seams and in 

sub-economic thick coal seams. Without MSC technology, very little future 

development is expected to take in these areas. Figure 1-13 shows the gas-inplace and technically recoverable coalbed methane resource estimates for three 

areas of the PRB where multi-seam technology is vital for development. 

9. Multiple coal seam well completions, developed and successfully applied in other 

CBM basins, have not been widely successful in the Powder River Basin. CBM 

operators in the Powder River Basin, recognizing the potential of MSC 

technology, have attempted to implement multi-seam well completion techniques 

developed in other coalbed methane plays. The results, however, have been 

Montana

Gas-In-Place 5.9 Tcf

Tech. Recoverable 5.3 Tcf

w/MSC Technology

Partition 7

Gas-In-Place 6.3 Tcf

Tech. Recoverable 3.6 Tcf

w/MSC Technology

Partition 11

Gas-In-Place 2.5 Tcf

Tech. Recoverable 2.1 Tcf

w/MSC Technology

JAF02188.PPT

13

10 9

12

11

7 8

6 5 4

3 2

1

Montana

Wyoming

Montana

Gas-In-Place 5.9 Tcf

Tech. Recoverable 5.3 Tcf

w/MSC Technology

Partition 7

Gas-In-Place 6.3 Tcf

Tech. Recoverable 3.6 Tcf

w/MSC Technology

Partition 11

Gas-In-Place 2.5 Tcf

Tech. Recoverable 2.1 Tcf

w/MSC Technology

JAF02188.PPT

13

10 9

12

11

7 8

6 5 4

3 2

1

Montana

Wyoming
23

disappointing due to the challenges arising from the geologic and reservoir 

conditions unique to the Powder River Basin—shallow, underpresssured, lowrank (low strength) coals surrounded by water-bearing aquifers. These reservoir 

conditions cause standard cased hole well drilling and completion practices to 

create extensive damage to the coal face and call for a set of practices and 

technologies appropriate to overcoming these unique reservoir conditions. 

 An initial or cursory review of the use of well completion practices in other basins 

with multiple coal seams shows that this development approach, when properly 

adopted, can be successful. The operators in each of these basins have 

modified the procedures and technologies to the specific geologic and reservoir 

conditions of the coals in each basin. Similar types of modifications are required 

to successful apply MSC technology in the PRB. 

* * * * * 

This study provides a major update to previous work by DOE/Advanced 

Resources International for the Powder River CBM play. The primary differences 

between this report and previous studies are: (1) incorporation of MSC technology 

for CBM development in this basin; (2) the inclusion of thin coal seams in large 

areas of the basin; (3) expanding the study area particularly in Montana; (4) developing an updated methane adsorption isotherm specific to PRB coals; and, (5) using 

a revised outlook for future gas prices and for the basis differential for the PRB. 

Each of these changes helps provide a more comprehensive, up-to-date 

assessment of the resource potential and technology impacts related to coalbed 

methane development in the Powder River Basin. 

The analysis clearly shows that advanced MSC technology can help improve the 

outlook for CBM in the Powder River Basin by improving the reserves-per-well, and 

by reducing environmental impact due to drilling fewer wells. There is sound reason 

to believe that, with a well designed and executed field R&D project, MSC 

technology will work in the PRB. As documented herein, MSC technology works in 

other CBM basins (such as the Warrior Basin) and is essential for making CBM 
24

development in these basins economic. There is no intent to overestimate the 

natural gas (CBM) recoverable from the PRB in this report. Rather, the purpose of 

the report is to estimate the impacts of a successful technology program, and 

industry's subsequent implementation of that program, throughout the PRB. While 

there is uncertainty associated with all field R&D, pursuing MSC technology is one 

area that offers both a high potential for success and a high value. 

Other actions, however, are still required to reach optimum development of this 

major domestic natural gas resource. These actions include improving market 

access for the produced natural gas, reducing gathering costs, establishing optimum 

well spacing, resolving the gas content and gas saturation issues (particularly for the 

deeper coals), and developing lower-cost water management options. These topics 

set the stage for further actions and technology development, all leading to more 

optimum production of the basin’s vast coalbed methane resource. 
25

SECTION 2. STUDY APPROACH AND METHODOLOGY 

2.1 Basin Area 

The Powder River Basin is one of a series of coal-bearing basins along the 

Rocky Mountains, stretching from northern New Mexico to central Montana. The 

basin covers approximately 28,500 square miles, with about one-half of this area 

underlain by producible coals. The basin is bounded on the east by the Black Hills 

uplift, on the north by the Miles City Arch, on the south by the Laramide Mountains, 

and on the west by the Big Horn Uplift and the Casper Arch. 

The bulk of coalbed methane activity to date has been in the east and central 

portions of the basin, around the town of Gillette, in Campbell County, Wyoming. To 

date, over 14,000 coalbed methane wells have been drilled in the Powder River 

Basin, providing a wealth of data for establishing the geologic setting and 

characteristics of the Wasatch and Fort Union Formation low-rank coals in this 

basin. However, the great bulk of the basin, particularly the deeper coals, still 

remains underdeveloped, requiring considerable extrapolation of the data and well 

performance for assessing the full basin. 

Figure 2-1 shows the outline of the Powder River Coal Field and coalbed 

methane basin in Wyoming. 

2.2 Basin Structure 

 The eastern flank of the Powder River Basin dips gradually toward the basin 

center at an average of 1.5o

 and is characterized by occasional normal faulting and 

folding (Figure 2-2). The basinal axis runs along the steeper western and southern 

margins, where the basin terminates against a complex of basement thrusts and 

reverse faults, as shown on the generalized cross-section of the Powder River Basin 

(Figure 2-3). 
26

Source: “Coalbed Methane Activity in the Powder River Basin, Wyoming”, Wyoming State Geologic Survey. 

Figure 2-1. Coal Basins of Wyoming. 
27

Figure 2-2. Regional Structure and Tectonic Map of the Powder River Basin. 

Source: Blackstone (1981, 1988)

Montana

Wyoming
28

 Source: Montgomery, 1999. 

Figure 2-3. Regional Cross-Section of the Powder River Basin. 

Source: Law, Rice and Flores, 1991. 

Figure 2-4. Upper Cretaceous and Tertiary Stratigraphic Chart 

for Powder River Basin. 

SYSTEM

SERIES

STRATIGRAPHIC UNIT

Tertiary (Part)

Oligocene Eocene Paleocene

Upper

Cretaceous

(Part)

Lance

Formation (Part)

White River Formation

Wasatch

Formation

FORT UNION

FORMATION

Tongue River Member

Lebo Shale Member

Tullock Member
29

2.3 Basin Stratigraphy 

The Powder River Basin (PRB) is filled with thick tertiary-age marine and fluvial 

deposits. The tertiary units contain the coal-bearing Fort Union and Wasatch 

formations are the topic of this study (Figure 2-4). 

The Tongue River Member, consisting of sandstone, conglomerate, siltstone, 

limestone, and coal, is the principal coal-bearing unit of the Fort Union Formation. 

The Tongue River Member contains a large number of distinct coal seams, ranging 

from a few feet to over 100 feet in thickness (Figure 2-5). 

The Tongue River Member can be further divided into upper and lower units. 

The Upper Tongue River unit contains the Smith/Swartz, Anderson (Deitz), Canyon 

(Monarch), Wyodak (where the Anderson and Canyon have merged), the Big 

George and the Cook (Carney) seams. The Lower Tongue River unit contains the 

Wall, Pawnee, Cache, and deeper coal seams. 

A series of Wasatch Formation coals exist on the western edge of the basin and 

include the Cameron, Felix, and Ucross seams. These coals coalesce into a thick 

coal package at Lake Desmet. 

In the Montana portion of the PRB, the Tongue River Member coals become 

shallower and outcrop. Several deeper seams, without exact equivalents in the 

Wyoming portion of the basin, become available for CBM development in Montana, 

including the Knobloch coal seam, which has been given particular attention in this 

study. 
30

Figure 2-5. Coal Bearing Units of the Tongue River Member 

of the Fort Union Formation. 

Source: WOGCC, 2002.
31

2.4 Reservoir Parameters 

Knowledge of the coal seam reservoir parameters is integral to understanding 

how CBM wells will perform. Several properties, including coal depth and thickness, 

pressure gradient, gas content, and gas saturation, were assessed to estimate gasin-place for each coal seam in each township. Water in-place was estimated using 

coal fracture and matrix porosity. Reservoir permeability provided estimates of 

recoverable gas and water, and their timing. Lastly, “type wells” constructed from 

over 1,400 Powder River Basin CBM wells were modeled using a CBM reservoir 

simulator to estimate gas and water production streams over a 10-year well life. 

Considerable more information on the assembly of key reservoir parameters and the 

assessment methodology used is provided in the original basin study.1

As an example of detailed information required for this comprehensive analysis, 

the reservoir properties for a CBM development area in the east-central portion of 

the Powder River Basin are shown in Table 2-1. 

Table 2-1. Representative PRB Reservoir Properties*. 

Free Gas Saturation Porosity 

Coal 

Seam 

Gas 

Content 

Pressure 

(Top of Coal) Fracture Matrix Fracture Matrix 

 (cf/t) (psi) (%) (%) (%) (%) 

Anderson 30 141 8 10 0.2 1.5 

Canyon 36 171 7 7 0.4 3.0 

Wyodak 41 200 5 10 1.0 6.0 

Cook 52 260 0 1 0.1 2.4 

Wall 63 340 0 0 1.0 10.0 

Pawnee 82 460 0 0 0.5 5.0 

Cache 94 560 0 0 0.5 5.0 

*For one major PRB partition area, as modified/updated 
32

2.4.1 Regional Pressure Gradient 

A regional pressure gradient versus depth relationship for PRB coal seams, 

Figure 2-6, was constructed to establish reservoir pressure for each of the coal 

formations. This was generated using: 

• Detailed hydrology data and pressure mapping by the Wyoming Bureau of 

Land Management (BLM), 

• Actual pressure data from basin producers, and 

• History matching of the pressure gradient data using long-term (4+ year) gas 

and water production in the PRB. 

2.4.2 Gas Content 

Gas content and isotherm data, appropriate for the low rank coals of the PRB, 

were assembled from the following sources: 

• Recently collected gas content and isotherm data by industry, the United 

States Geological Survey (USGS), and the Bureau of Land Management 

(BLM). 

• Gas content and isotherm data collected by Advanced Resources 

International in analogous low rank coals in other basins, and 

• History matching of long-term (4+ year) gas and water production data in the 

PRB to establish gas content values and a volumetrically consistent 

isotherm. 

The coalbed methane isotherm used in this study, shown in Figure 2-7, is an 

update of the isotherm used in the previous study. For comparison, a gas content 

isotherm from past data collected by the BLM in Wyoming is shown in Figure 2-8. 
33

Figure 2-6. Reservoir Pressure Profile Used for PRB Study. 

Figure 2-7. Gas Content Isotherm Used for MSC Study. 

0

20

40

60

80

100

120

140

0 200 400 600 800 1000

Pressure (psia)

Gas Content (scf/ton)

0.0

0.6

1.2

1.8

2.4

3.0

3.6

4.2

Gas Content (scf/cf)

JAF2003008.XLS
34

Range of values represents +1 sigma in the data. 

Figure 2-8. Average Synthesized Adsorption Isotherm for Coals 

in the Powder River Basin. 

2.4.3 Gas Saturation 

The nature of early time water and gas production was used to establish whether 

the PRB coals were undersaturated, fully saturated, or contained free gas in the 

pore space: 

• A series of fourteen individual coal seams and production data sets were 

assembled involving gas and water production data from over 1,400 PRB 

CBM wells. 

• History matching of production data was used to establish the level of gas 

saturation and presence of free gas in the coal cleat and matrix system. 

Overall, the study determined that the coals are fully saturated with methane (at 

the reduced reservoir pressure conditions that generally exist in the basin) and that 

modest amounts of free gas exist in the matrix porosity and coal cleat (fracture) 

porosity systems in certain of the seam/partition data sets. 

0

20

40

60

80

100

120

0 200 400 600 800 1000

Pressure (psia)

Gas Content (scf/ton)

0.0

0.7

1.4

2.1

2.8

3.5

4.2

Gas Content (scf/cf)

Source: Wyoming EIS, 2002.
35

However, operators report that low gas content and undersaturated conditions 

may exist for certain of the deeper coals in the central portion of the basin, south of 

Gillette. Collection, analysis, and reporting of additional gas content data would help 

define the potential gas content problem areas and seams in the basin. 

2.4.4 Coal Fracture and Matrix Porosity 

History matching of water production was used to establish the fracture and 

matrix porosity for the PRB coals: 

• In general, the coal cleat (fracture) porosity in the coals ranges from 0.1 to 1 

percent, consistent with other data on fractured coals and reservoirs. 

• The matrix porosity for these low rank coals varies widely, ranging from 1 to 

10 percent, with highest matrix porosity in the Wyodak and Wall coal seams. 

High coal matrix porosities would account for the relatively high water production 

from otherwise thinner (25 to 30 feet) seams, such as the Wall coal seam. 

2.4.5 Coal Permeability 

In general, the coal cleat (fracture) permeability of PRB coals is favorable, 

ranging from 35 to 500 millidarcy (md). Coal matrix permeabilities are considerably 

lower and variable, ranging from 0.001 to 1.0 md. However, even the lower end of 

the range for cleat and matrix permeabilities for these coals in the PRB is sufficient 

to support reasonable 10-year gas recoveries (technically recoverable) of 50 to 80+ 

percent of the gas-in-place. 

2.4.6 Estimating Gas and Water Production 

Gas production and recovery were estimated on a per well basis using data 

gathered from actual producing Powder River Basin CBM wells. Producing wells 

were sorted by seam and their production streams were normalized from a data 

base of over 1,400 CBM wells with sufficient production data and confinement using 

time-zero plots. Figure 2-9 illustrates this data set for a group of 164 closely spaced 
36

Wyodak coal seam wells in the eastern portion of the basin. This process provided 

14 history matched production streams from which permeability, coal porosity, gas 

and water saturation, and other data could be obtained via history matching. 

• History matching was performed using a state-of-the-art reservoir simulator, a 

triple porosity and triple permeability finite difference model, specifically 

developed for coalbed methane production and reserve assessments. 

• The history matched wells were extended in time to provide 10-year coalbed 

methane and water production rates and estimates of ultimate gas and water 

recovery (Figure 2-10). 

• The 14 history matched wells were further modified using actual depth and 

thickness values for major seams, providing unique type wells for each major 

seam in each township of the basin. 

• The gas and water production streams and recovery factors from these type 

wells were combined into distinct packages of coal (discussed further below) 

to create a series of multiple-seam completed CBM wells. 

2.5 Multi-Seam Coal Model 

2.5.1 Coal Inventory 

A revised township-level coal database was assembled for all seams within the 

Powder River Basin, for coals thicker than 5 feet and deeper than 200 feet. Depth 

and thickness data for thick coal seams (seams thicker than 20 feet) were from an 

update of the original coal seam database. Data for thin coal seams are sparse 

however, and because current CBM completion practices bypass these seams, 

previous studies have not included these data. To account for these thin coal 

seams, 270 recent Powder River Basin CBM well logs that span the full Fort Union 

coal interval throughout the CBM play were evaluated. Depth and thickness data for 

all coal seams permitted correlation with ARI’s existing database. Ultimately, well log 

data representing over 9,700 square miles of the CBM play were collected. 
37

Areas of missing data were primarily along the basin margins. These townships 

were often adjacent to areas with little or no coal, indicating that little CBM resource 

may exist in these basin areas. With time, exploratory CBM programs may help to 

fill the gaps in the database. 

Figure 2-9. Wyodak Coal Seam Time-Zero Plot. 
38

Figure 2-10. Wyodak Type Well History Match. 

The other notable absence in data is along the northern edge of the play. Much 

of this area is on the Crow Indian Reservation that has not yet been explored or 

drilled for coalbed methane. Figure 2-11 displays the townships from which data 

were collected and used by this study. 

2.5.2 Coal Packages and Completion Criteria 

For consistency and comparison, three distinct coal packages were defined 

(each with a maximum of 4 individual coal seams). These were: 

• Package #1: The shallow Upper Fort Union, consisting of Wasatch formation 

seams through Anderson coal seams; 

• Package #2: The deeper Upper Fort Union, consisting of Canyon through 

Cook seams; and 

• Package #3: The Lower Fort Union, consisting of the Wall and deeper coal 

seams. 
39

To be included in one of the coal packages in Wyoming, a coal seam had to be at 

least 300 feet deep and have a thickness of 10 feet or more. In Montana, the depth 

and thickness criteria were relaxed to include seams at least 200 feet deep and 5 

feet thick to more fully capture the coal resource in the northern part of the basin. In 

Montana, special efforts were made to collect and include stratigraphically deeper 

coal seams, such as the Knobloch seam, which exist near the northern edge of the 

Powder River Basin CBM play. 

Figure 2-12 provides an example of the coal seam database assembled for this 

study, showing the individual coal seams and the aggregate coal thickness for each 

coal package. 
40

Figure 2-11. Map Showing Townships from which a CBM Well Log 

Was Analyzed for this Report. 

Few logs exist for areas in the northern Montana region and along the western 

edge of the play. 

JAF02194.PP
41

Figure 2-12. PRB Coal Database for 24 Townships in Partition #8, 

Northeast Powder River Basin. 

2.5.3 Volumetric CBM Database 

With the reservoir data in hand, volumetric calculations were performed seam-byseam for an 80 acre well in each township to estimate: 

• Gas-In-Place 

• Technically Recoverable CBM Resource 

• Ultimate Water Production 

The gas and water production streams from three packages of multiplecompleted coals in T54N R76W are shown in Figure 2-13. 
42

2.6 Basic Cost Model 

This study uses an updated version of ARI’s coalbed methane cost and 

economic model, CECON (Coalbed Economics), to assess the feasibility of 

developing coalbed methane with multi-seam well completion technology. The 

model contains four main components: (1) basic capital costs; (2) basic operating 

and maintenance costs; (3) gas transportation and compressions costs; and (4) 

other costs. 

The economic model incorporates forecasts for future natural gas prices (at the 

Henry Hub), current and anticipated Wyoming basis differentials, and royalties, 

production taxes, and other factors that impact CBM costs and economics. The 

economic model (before federal income tax; BFIT) is an industry-standard 

discounted cash flow (DCF) model that provides both an internal rate of return and 

the net present value (NPV) of an investment at various discount rates and at 

various net gas prices. 

2.6.1 Capital Costs for PRB CBM Well 

The basic capital costs for a PRB CBM well include outlays for land, permits, 

drilling and completion, infrastructure, and water management. These costs vary 

considerably by well depth, location and number of seams completed. For 

illustrative purposes, Table 2-2 shows the costs for a Powder River Basin coalbed 

methane well at 960 feet of depth, spaced on 80 acres, with 2 wells per pad. Capital 

costs are per well, assuming a 16 well, 8 pad development unit. Gas treating and 

compression is assumed to be provided by a third party contract and is included in 

annual operating costs. 

This study assumes that impoundments and shallow re-injection would be used 

for produced CBM waters. (For a full description of the capital cost module and 

other water disposal alternatives, see DOE/NETL-2003/1184). The basic capital 

costs for the example PRB CBM well are estimated at $141,190, as shown in 

Table 2-2. 
43

Table 2-2. Capital Costs for Illustrative CBM Well, Powder River Basin. 

Cost Item Capital Costs 

Land Costs and Permits $13,000 

Well Drilling and Completion (@960 feet) (1) 91,070 

Water Gathering (2) 10,210 

Water Disposal (3) 10,290 

Electric Power, including cable (4) 8,460 

Gas Gathering (5) 7,820 

Miscellaneous 340 

Total $141,190 

(1) Includes packer rental, cost of enhancement, and perforation charges. 

(2) Allocated based on small diameter water gathering piping of 2,000 feet per well (including 

common trenching and survey for water, gas and electrical cable), central water transportation (2 

lines) of 10,000 feet, right of way for 42,000 feet, two surface pumps; and, contingency, insurance 

and other of 10 percent. 

(3) Allocated based individual well’s share of the construction of a central processing facility and 

impoundment pond or shallow reinjection well. 

(4) Allocated based on central 3-phase power installation costs of $75,000 per unit, electrical 

cable of 2,000 feet per well, and contingency, insurance and other of 10 percent. 

(5) Allocated based on small diameter gas gathering piping of 2,000 feet per well, central gas 

transportation (2 lines) of 10,000 feet, and contingency, insurance and other of 10 percent. 
44

Figure 2-13. Natural Gas and Water Production (as modeled) for One 

Township in Partition #8 Northeast Powder River Basin. 
45

2.6.2 Operating & Maintenance Costs for PRB CBM Well 

The basic lease and well operating and maintenance (O&M) costs for a Powder 

River coalbed methane well vary by year of production, with higher costs during the 

initial years because of more frequent well enhancements and pump replacements. 

O&M Costs/Well* 

Annual Monthly 

Year 1 $26,540 $2,210 

Years 2 - 4 $16,990 $1,420 

Years 5 - 10 $11,210 $930 

TOTAL (Years 1 - 10) $144,770 $1,210 

*Includes G&A charge of 20% for engineering, accounting, legal and other indirect costs. 

For example, assuming CBM recovery of 0.58 Bcf (gross) per well, the O&M/G&A 

costs are $0.25 per Mcf. 

2.6.3 Gas Transportation, Compression, and Fuel Use 

The costs for gas treatment, compression, and transportation are subtracted from 

the PRB netback price to establish a PRB CBM wellhead price. The costs will vary, 

depending on the gathering system charges for transporting natural gas from the 

compressor to the Colorado Interstate Gas (CIG), or another hub, and on the nature 

and extent of contracted third-party compression. These costs depend on the 

location of the CBM development in the PRB, as follows: 

• A charge of $0.43 per Mcf is used for third party compression and 

dehydration (assuming no lease compression) and for transportation, for the 

central and southern portions of the PRB (Partitions #1, 2, 3, 4, and 5). 

• A charge of $0.57 per Mcf is used for third party compression and 

dehydration (assuming no lease compression) and for transportation, for the 

northeast and southwest portions of the PRB (Partitions #6, 8, 9 and 10). 
46

• A charge of $0.77 per Mcf is used for third party compression and 

dehydration (assuming no lease compression) and for transportation, for the 

northwest and western portions of the PRB (Partitions #7, 11, 12 and 13). 

A fuel adjustment (shrinkage) for operating gas powered compressor stations, 

estimated at 4 to 6 percent of gross production, is subtracted from the sales volume. 

A second fuel adjustment (shrinkage), involving the Btu adjustment for CBM, 

generally 2 to 8 percent (to account for 920 to 980 Btu content gas), is also 

subtracted from the sales volume. 

2.6.4 Other Considerations 

Royalties. Royalty payments for PRB CBM production depend on mineral 

ownership, as set forth below: 

• Royalties on Federal lands are 12.5 percent. 

• Royalties on state lands are 16.7 percent. 

• Royalties on private lands range from 15 to 20 percent. 

• State Severance and Ad Valorem Taxes. State and county tax payments for 

PRB CBM production are state specific, as set forth below: 

• Wyoming severance and ad valorem taxes are 12 percent. 

• Montana severance taxes are 9.3 percent. 

2.6.5 Basis Differentials 

Because of higher transportation costs and other market conditions, the gas price 

at the CIG (or another Wyoming/Rocky Mountain) Hub is discounted from a marker 

price, set by the Henry Hub or NYMEX. (This is commonly called the basis 

differential). Currently (mid-March, 2003), with the Henry Hub gas price at $5.83 per 

MMBtu, the Wyoming Pool Hub is at $4.08 per MMBtu and the Opal Hub is $4.01 
47

per MMBtu, for a basis differential of about $1.80 per MMBtu. Historically, the basis 

differential has been closer to $0.80 per MMBtu. 

2.6.6 Economic Scenarios 

Two wellhead netback/basis differential scenarios were evaluated. For both, the 

Henry Hub natural gas price was anchored at $3.50/Mcf for the life of the project; 

however, the basis differential was modeled as follows. 

• Scenario #1. Basis differential remains constant at $1.80/Mcf. 

• Scenario #2. Basis differential narrows from $1.80/Mcf to $0.80/Mcf, over a 

three-year period. 

Scenario #1 represents a limiting case. A differential of $1.80/Mcf is high but 

represents the conditions that producers have faced of late. The $0.80/Mcf basis 

differential in Scenario #2 represents a situation in which new pipelines are 

constructed, providing Powder River Basin gas access to additional markets and 

enabling the basis differential to return to historical levels. 

* * * * * 
48

SECTION 3. PERFORMANCE OF MULTI-SEAM CBM WELL COMPLETIONS IN 

THE POWDER RIVER BASIN 

3.1 Background 

 One of the objectives of this study is to evaluate the use and performance of 

currently available multi-seam completion practices for coalbed methane in the 

Powder River Basin. This task involved: 

1. Reviewing technical papers and state commission filings on the number and 

types of multi-seam completions in the PRB; 

2. Holding discussions with a select group of basin operators to identify and discuss 

their use of multi-seam completions for CBM recovery; 

3. Collecting and assessing data on the performance of this technology, to the 

extent that basin operators were willing to disclose this data; and 

4. Identifying aspects of multi-seam well completion technology requiring 

improvements for successful application to the Powder River Basin. 

In addition, ARI staff met with basin operators to: (1) establish their perceived value 

and need for improved multi-seam completion technology; and, (2) gain an 

‘expression of interest’ with respect to participating with DOE/NETL in potential 

R&D/field tests of an improved version of this technology appropriate to the coal 

seams of the Powder River Basin. 

3.2 Overview of CBM Well Completions 

The dominant well completion method for coalbed methane wells in the PRB is 

open-hole, single zone completion. As shown in Figures 3-1 and 3-2, this method 

provides a low cost, relatively simple access to a coal seam. In brief, the completion 

procedure is: 

• Set surface casing to 60 feet or 10 percent of the well depth, 
49

• Drill into the top of 2 to 3 feet of the target coal seams, using a light mud 

system, 

• Run and cement casing; then drill out and under-ream the coal, and 

• Enhance the coal, primarily to clean the coal face and remove near wellbore 

damage using injection and circulation of high rates of water. 

While using single-zone (or single seam) well completion technology is relatively 

simple, it has a number of limitations: 

• It bypasses the numerous thin (less than 20 feet) coal seams in the basin, as 

illustrated in Figure 3-3; 

• It leads to the drilling of a much larger number of CBM wells, with increased 

capital costs and land disturbance; and 

• It causes large areas of the basin to remain uneconomic, particularly when 

the basis differential is high and because of the relatively high gas gathering 

costs in the Powder River Basin. 
50

Figure 3-1. Typical Well Completion Practice, Powder River Basin 

Figure 3 Single- 
51

Coals less than 20 feet thick are not completed. 

Figure 3-3. Well Log Showing Typical Fort Union Stratigraphy. 

A striking illustration of these problems is the analytical map showing the large 

areas of the basin that are currently uneconomic or only marginally economic to 

develop with current single-seam well completion technology (Figure 3-4). This map 

was submitted to the State of Wyoming by one of the basin’s main CBM operators. 

It dramatically illustrates, for the northern portion of the basin where this operator is 

active, the critical need for multi-seam well completion technology. 
52

Several options adapted from other CBM basins exist for multi-seam well 

completion technology, as illustrated in Figures 3-5 and 3-6. 

• In the first option, the approach is to complete two (or more) coal seams as 

open-hole, and then hang a perforated steel liner across the open-hole 

interval. A variant on this option is to hang a PVC liner, and then under-ream 

the liner to assure access to the coal. 

• In the second option, the approach is to drill and case across the coal, and 

then perforate the casing to gain access to the multiple seams. 

• The third option is to use a combination of the above. The deepest coal is 

completed open-hole; casing is set and the up-hole coals are perforated. 

The problem is that these relatively straight forward applications of multi-seam 

well completion technology have not proven to be successful in the Powder River 

Basin. In many cases, a multi-seam well produces less than a single-seam well 

because of damage to the coal. Additional discussion of this situation follows. 
53

Figure 3-4. Map Submitted by Powder River Basin Operator(s) Showing Areas Where 

MSC Technology is Vital for Future CBM Development. 
54

Figure 3-6. Multi-Seam Completion Option #2 

Figure 3-5. Multi-Seam Completion Option #1 
55

3.3 Field Case Studies 

To better understand the performance and problems with this completion 

strategy, three significant multi-seam CBM well completion projects in the PRB were 

examined. These projects are located in distinct areas in the northern Wyoming 

portion of the Powder River Basin (Figure 3-7). They represent the current state of 

multi-seam well completion technology and performance in the basin. 

3.3.1 Methodology 

Production data from the wells in each project were collected and aggregated 

using “time-zero” plots. From this, the average daily rate (production / actual days 

on) and cumulative monthly recovery are calculated for each well and then averaged 

to create a series of typical CBM wells for the project. The single-seam completions 

serve as the control wells for each project, establishing a baseline of expected 

production from each coal seam. The performance of multi-seam well completions 

(producing from these same coal seams) is established using this control set of 

single-seam wells. 

In all three field case studies, the single-seam CBM wells are completed openhole. Casing is set just above the coal interval and the coal itself is underreamed. 

After flushing the coal with high rates of injected water, the CBM well is placed on 

production. For the multi-seam wells, the lowest coal (the primary target) is 

completed open-hole. Shallower seams are then accessed through perforations in 

the casing. 

In an ideal multi-seam well, all completed zones would contribute their full 

potential to CBM production. Formation damage and ineffective perforation during 

completion, however, appear to limit production mainly to the open-hole primary 

seam, which itself appears to be often damaged. 

The data for the three field case studies were assembled from publicly available 

state records and data systems (WOGCC, 2003). 
56

Figure 3-7. Location Map for Multi-Seam Case Studies. 
57

3.3.2 Case Study #1 

Study Purpose and Wells. Case Study #1 involves a side-by-side comparison of 

the performance of nine single-seam completed Canyon coal wells and five multiseam completed Canyon, Cook and Wall coal wells. All of the wells are in S.16 of 

T55N R75W, providing excellent geologic and reservoir uniformity to the comparison 

of performance. 

The wells are operated by Yates Petroleum, one of the Powder River Basin’s 

larger and technically strong operators. The Case Study #1 field site is located in 

the north-central portion of the basin, as shown in Figure 3-7. The location of the 

nine single-seam Canyon wells and the five multi-seam Canyon-Cook-Wall wells are 

shown in Figure 3-8. 

Target Coal Seams. The main target, the Canyon seam, is a 30 to 40 foot coal at 

400 to 500 feet of depth. The Cook seam (called Lower Canyon by the operator) in 

this area is a 40 foot coal at 700 to 750 feet of depth. The Wall seam is a 25 foot 

coal at 800 feet of depth. Ideally, producing the Cook and Wall seams with the 

Canyon seam, a package of nearly 100 feet of net coal would lead to a well with gas 

flow rates and reserves about three times higher than producing the Canyon seam 

alone. 

Single-Seam Well Completion Strategy and Performance. The nine single-seam 

Canyon wells are completed as open-hole, single-seam wells, as shown for one of 

the case study wells, the Spotted Horse CS State #13 (Figure 3-9). These wells are 

moderate CBM producers, having recovered 54 MMcf of gas during their first year 

on line and 86 MMcf during their first 18 months of production, on average. The 

wells are currently producing at 184 Mcfd, on average. This set of wells provides the 

control set against which current multi-seam well completion technology is judged for 

this area of the basin. 
58

Figure 3-8. Location of Yates CBM Wells Included in Case Study #1. 
59

Figure 3-9. Case Study #1 Single-Seam Well. 

Lowest coal is completed open-hole. 
60

Multi-Seam Well Completion Strategy and Performance. The five multi-seam 

wells are completed with the lowermost Wall coal kept open-hole and with the 

shallower Cook (Lower Canyon) and the main Canyon seams cased and perforated, 

as shown for one of the case study wells, the Spotted Horse CS State #3, in 

Figure 3-10. 

The performance of the five multi-seam wells has been disappointing. The 

cumulative gas production during their first year online is 40 MMcf and only 72 MMcf 

during their first 18 months, on average. These multi-seam wells, in spite of 

presumably being in contact with nearly three times as much net coal as the singleseam wells, have a lower recovery than the single-seam Canyon well, as shown in 

Figures 3-11 and 3-12. 

Poor production from the multi-seam well is not due to slow or inefficient 

dewatering, as shown in Figure 3-13. Instead, the interpretation is that the 

application of currently available multi-seam technology has created so much 

damage (or is so ineffective) that it has failed to efficiently connect any additional 

coal to the wellbore and may have actually has damaged the performance of the 

main coal. 

It would be instructive to return to this set of Case Study #1 wells in about a year. 

This would help establish whether the recent, increasing rates of gas production for 

the multi-seam wells suggest some amount of cleanup of the perforated coals, or 

some other phenomenon. 
61

Table 3-1. Average Case Study #1 Single Seam Canyon Well and Multi-Seam 

Canyon/Cook/Wall Well, After 12 and 18 Months of Production. 

(The numbers of wells included in the average are in parentheses). 

 Single Seam Wells Multi-Seam Wells 

Canyon (9) Canyon/Cook/Wall (5) 

Cumulative Recovery 

(MMcf) 

@ Month 12 

@ Month 18 

54 

86 

40 

72 

Daily Rate (Mcfd) 

@ Month 18 184 134 

Source: WOGCC data base, 2002. 
62

Lowest Coal is completed open-hole. Access to up hole seams is through perforation. 

Figure 3-10. Case Study #1 Multi-Seam Well. 
63

Figure 3-11. Time-Zero Production Rate for Average Single-Seam Canyon Well and 

Average Multi-Seam Canyon-Cook-Wall Well. 

Figure 3-12. Time-Zero Cumulative Production for Average Single-Seam Canyon Well 

and Average Multi-Seam Canyon-Cook-Wall Well. 
64

Figure 3-13. Time-Zero Water Production Rate for Average Single-Seam Canyon Well 

and Average Multi-Seam Canyon-Cook-Wall Well. 

3.3.3 Case Study #2 

Study Purpose and Wells. Case Study #2 involves a side by side comparison of 

23 single-seam completed wells and 19 multi-seam completed wells. The wells are 

clustered in a 10 section area, in T65N, R74W and T56N R75W. The location of the 

Case Study #2 CBM wells is provided in Figure 3-7 and Figure 3-14. This large well 

population in a relatively confined area provides a valuable data set for examining 

the performance of single seam and multi-seam technology. 

The wells are operated by Huber, one of the largest and technically most 

sophisticated operators in the basin. The Case Study #2 field site is located in the 

northern portion of the basin, close to the Wyoming and Montana border. 

Target Coal Seams. The primary coal seam targets for the 23 single-seam 

completed wells are the Wall (17 wells) and the Cook (6 wells). In this area, the Wall 

coal is 15 to 30 feet thick at a depth of 680 to 825 feet. The Cook coal is 15 to 35 

feet thick at a depth of 580 to 900 feet. 
65

The 19 multi-seam completed wells combine the Cook and Wall seams with the 

Canyon (Upper Cook) in 8 wells and combine the Cook and Wall seams with the 

Canyon and Pawnee in 11 wells. The shallower Canyon coal in this area is 30 to 35 

feet thick at a depth of 240 to 550 feet. The deeper Pawnee coal is 10 to 40 feet 

thick at a depth of 590 to 1,010 feet. 

Figure 3-14. Location of Huber CBM Wells Included in Case Study #2. 

Successfully combining the Canyon, Cook and Wall (plus the Pawnee) in the 

multi-zone completed wells should lead, ideally, to a well with about three times as 

much gas production as a single-zone Wall or Cook completion. 
66

Single-Seam Well Completion Strategy and Performance. The single-zone Wall 

and Cook wells are completed open hole. After the first eight months online, the 

average Wall CBM well has recovered 37 MMcf and is producing 281 Mcfd; the 

average Cook CBM well has recovered 29 MMcf and is producing 144 Mcfd. 

Production continues to increase for both sets of wells and dewatering continues. 

Multi-Seam Well Completion Strategy and Performance. The multi-zone wells 

are completed with the lower-most coal kept open-hole and the shallower coals 

cased and perforated. The performance of the multi-zone wells compared to the 

single-seam wells is extremely disappointing, as shown on Figures 3-15 and 3-16. 

Early-time data suggest that limited dewatering is not to blame for poor well 

performance, Figure 3-17. 

• The average three-zone—Wall, Cook and Canyon—well has recovered only 

16 MMcf and is producing 107 Mcfd after eight months online. Even if the 

Canyon seam made no contribution, this well should have recovered about 

66 MMcf and should be producing 425 Mcfd, based on comparable single 

seam well performances for the Wall and the Cook seams. (After 16 months 

online, the production rate for the average three-zone well is still only about 

160 Mcfd.) 

• The average four-zone—Pawnee, Wall, Cook and Canyon—well has 

recovered only 20 MMcf and is producing at 95 Mcfd after eight months 

online. (The longer term performance of the four-zone well provides some 

indication that the wells may be cleaning up. After 2 years online, the 

cumulative recovery for the four-zone well is 85 MMcf and the production rate 

has increased to and remained steady at about 150 Mcfd). 

The summary of the comparative performance of the Case Study #2 CBM wells 

is provided in Table 3-2 below, after their first eight months online. 
67

Table 3-2. Average Case Study #2 — Single Seam and Multi-Seam Wells, 8 

Months of Production. 

Single Seam Wells Multi-Seam Wells 

Wall (17) Cook (6) Canyon-Cook-Wall 

(8) 

Canyon-Cook-WallPawnee (11) 

Cumulative Recovery (MMcf) 

@ Month 8 37 29 16 20 

Daily Rate (Mcfd) @ Month 8 281 144 107 95 

The numbers of wells included in time-zero averages are in parentheses. 

Figure 3-15. Production Rate for Average Single-Seam Wells (Cook, Wall) and 

Average Multi-Seam Wells (Canyon-Cook-Wall, Canyon-Cook-Wall-Pawnee). 
68

Figure 3-16. Cumulative Production for Average Single-Seam Wells (Cook, Wall) and 

Average Multi-Seam Wells (Canyon-Cook-Wall, Canyon-Cook-Wall-Pawnee). 

Figure 3-17. Water Production Rate for Average Single-Seam Wells (Cook, Wall) and 

Average Multi-Seam Wells (Canyon-Cook-Wall, Canyon-Cook-Wall-Pawnee). 
69

3.3.4 Case Study #3 

Study Purpose and Wells. Case Study #3 involves the application of multi-seam 

technology to add additional coals, the Cook and the Anderson seams, to five 

existing single-seam completed CBM wells, initially completed in the Canyon coal. 

Three of the wells are in S.11 and S.12 of T52N R72W and two of the wells are in an 

adjoining area, S.18 and S.19 of T52N R73W. 

The wells are operated by Majestic Petroleum LLC, a small independent operator 

in the Powder River Basin. The Case Study #3 field site is located in the eastcentral portion of the basin, as shown in Figure 3-7 and Figure 3-18. 

Target Coal Seams. The main target, the Canyon seam, is a 60 to 85 foot coal at 

330 to 460 feet of depth. The shallower Anderson seam has 35 to 45 net feet of 

coal at a depth of 140 to 280 feet. Successfully adding and producing the Anderson 

coal seam with the Canyon would, ideally, lead to a well with about 50 percent 

higher gas production rates and reserves as a Canyon single-zone completion. 

Single-Seam Well Completion Strategy and Performance. The initial 

completions in the five Canyon coal seam wells were open-hole single-seam. After 

their first three years of operation, the five Canyon wells had recovered 168 MMcf of 

CBM (on average) and were still producing at about 100 Mcfd. 

Multi-Seam Well Completion Strategy and Performance. In August 2001, with 

gas production in modest decline (about 2 percent per month), the operator 

recompleted these wells to add the Anderson coal seam and began reporting the 

data on a commingled basis. For the five multi-zone recompletions, initial results 

were disappointing as production through the end of 2001 was less than expected 

from the Canyon seam alone. Through 2002, gas production returned to an average 

of 100 Mcfd early in 2002, and has fluctuated between 100 and 125 Mcfd during the 

past year. 

The latest performance of these recompleted, multi-seam wells is more 

encouraging, with the Anderson seam making an estimated contribution of about 40 
70

to 50 Mcfd. However, this is considerably less than would be expected from an 

efficiently completed Anderson coal well in this area. 

At the end of 18 months online, the Anderson well has recovered an estimated 

15 MMcf, as shown in Figure 3-19. (These estimates assume the continuation of the 

2 percent monthly gas production decline rate for the Canyon single-seam 

completion.) After 18 months, the typical Anderson CBM wells in this township, with 

the same coal thickness as the recompleted wells, would have recovered 36 MMcf, 

more than twice actual performance. 

The summary performance of the Case Study #3 CBM wells is provided in Table 

3-3 below, in MMcf of cumulative recovery for the average well: 

Table 3-3. Average Case Study #3 — Single-Seam and Multi-Seam 

Recompleted Wells. 

Cumulative Recovery 

(MMcf) 

Canyon Single-Seam 

Completion (5) 

Anderson Multi-Zone 

Recompletion (5) 

Total Well 

Performance (5) 

First 3 Years 168 - 168 

Last 18 Months 44 15 59 

Total to Date 212 15 227 
71

Figure 3-18. Location of Majestic CBM Wells Included in Case Study #3. 

3.3.5 Summary 

Attempts at effective multi-seam CBM completions in the Powder River Basin 

have met with disappointing results, thus far. Most often, the secondary seams 

simply fail to contribute to production. In a few cases, the extra completions actually 

cause the overall CBM production rates to drop below that expected from the 

primary seam. These problems must be overcome with an alternate strategy and 

approach to multiple-seam well completion technology. Successful application of 

MSC technology would enable the vast coalbed methane resource residing in subeconomic thick and thin coal seams in the Powder River Basin to be added to the 

nation’s natural gas reserves with fewer wells and less environmental disturbance. 
72

Figure 3-19. Average Case Study #3 Canyon CBM Well and Recompletion 
73

SECTION 4. APPLICATION AND PERFORMANCE OF MULTI-SEAM 

COMPLETION TECHNOLOGY IN OTHER CBM BASINS 

4.1 Background 

Developing and successfully applying multi-seam well completion (MSC) 

technology for recovering coalbed methane has long been a goal of operators and 

research organizations. For example, one of the initial CBM R&D projects of the 

Gas Research Institute (GRI) was the Methane from Multiple Coal Seams 

Completion Project at the Rock Creek field research laboratory in the Warrior Basin, 

Alabama (Figure 4-1). 

The motivation for developing multi-seam technology for completing the 

numerous coals in this basin was to improve the economics (breakeven price) of 

coalbed methane recovery in this basin, as shown in Figure 4-2. The figure shows 

that successful use of multiple coal seam completions would cut the costs, and thus 

the minimum breakeven price, for CBM in the Warrior basin by half. 

The multi-seam technology being developed in the Warrior Basin was linked and 

dependent on advanced stimulation technology. Together, these two technologies 

offered the promise of nearly tripling gas recovery per well, from 200 MMcf per well 

with single-seam technology to 600 MMcf per well with use of multi-seam technology 

and advanced hydraulic fracturing (Figure 4-3). 

The overall objective was to develop multi-seam completion technology and 

practices that could then be transferred and applied to the large CBM resource 

contained in the multiple, thin coal seams of the Central and Northern Appalachian 

basins, as shown in Figure 4-4. 

The Rock Creek Field Research Project demonstrated that completing all coal 

seams encountered in a single well bore would result in increased per well reserves 

compared to single-seam completions. Consequently, multi-seam completion 

became the strategy of choice in all coal basins with stacked coal reservoirs. 
74

Figure 4-1. Location of the Rock Creek Field Research Site, 

Warrior Basin, Alabama. 
75

Figure 4-2. Effect of Multiple Completion of Coal Seams on Breakeven 

Gas Price, Warrior Basin, Alabama. 
76

Figure 4-3. Objectives of Multi-Seam Completion Project. 
77

Figure 4-4. Multiple Completion Potential of Pennsylvanian Age Coals. 

The Powder River Basin (PRB) may well be the only basin where single-seam 

well completions are the standard completion method despite the presence of 

multiple coal seams. However, early multi-seam completion attempts in the PRB, 

based on completion strategies used in other coal basins, have largely been 

unsuccessful in establishing commercial gas rates, as discussed in detail in 

Chapter 3. 

To further understand why multi-seam completion methods used in other CBM 

plays aren’t applicable to the PRB, it is useful to review the various MSC technology 

options and how those options have been adapted to the unique coal distribution, 

thickness, and reservoir properties in each CBM basin. 
78

4.2 Current CBM Development Strategies 

Multi-seam well completions are used extensively in the San Juan, Warrior, Uinta 

and Raton basins. These basins also utilize hydraulic stimulations with sand 

proppant to enhance gas and water rates. (In addition to hydraulic stimulation, the 

dynamic open-hole cavity completion method is also used in the San Juan Basin.) 

The type and design of hydraulic stimulations vary considerably among the basins, 

reflecting differing geologic, and reservoir conditions. A summary of currently applied 

multi-seam completion technology in the San Juan, Raton, and Uinta, basins is 

provided in Appendix A. 

There are two reasons why most CBM wells require a propped, hydraulic 

stimulation: 

1. To overcome damage caused during drilling and cementing. Coal reservoirs are 

susceptible to invasion during well drilling and cementing. The permeable, 

under-pressured coals of the PRB suffer deep invasion and consequently can 

become severely damaged during drilling and cementing operations. 

2. To better connect the well bore with the natural fracture system. Coals are 

typically low permeability reservoirs with vertical, natural fractures providing the 

primary source for permeability. A vertical well intersects relatively few vertical 

fractures; therefore, flow to the well bore is limited without the benefit of a 

propped fracture system. Coals of the PRB have high inherent permeability and 

associated high natural flow potential, therefore, propped hydraulic stimulations 

are less important in the absence of damage caused by drilling fluids and 

cement. 

The Powder River Basin open-hole completion technology avoids exposing the 

coal seam to damaging drilling fluids and cement, thereby preserving its naturally 

high flow characteristics. However, given the high permeability and under-pressured 

nature of the Powder River Basin coals, the seams overlying the open-hole interval 

that have been cased will have encountered significant damage. Attempts to 

produce through the damaged zone by perforating have achieved limited success 
79

because the damage goes beyond perforation penetrations, and access to the coal’s 

quality flow characteristics is not achieved. 

In the Powder River Basin, the clays and shales interbedded with the coals are 

notoriously unstable. From an operational standpoint, even small shale or clay 

intervals in an open-hole completion create difficulties, causing potentially productive 

wells to be plugged and abandoned. Because of this, large open-hole completions 

containing multiple coals seams are not a viable option (today’s technology) in the 

Powder River Basin. 

Although large interval hydraulic stimulation is used in the San Juan and Uinta 

basins for CBM development, this approach is also not applicable to the PRB. The 

stratigraphic section in the PRB has aquifers interbedded with the coal seams. Both 

the aquifers and the coal seams could be affected by large interval stimulations. The 

inclusion of stimulated aquifers in the producing section would hinder (or even 

preclude) efficient dewatering of the coal seams. 

4.3 Testing Multi-Seam Well Completion Technology in the Warrior Basin 

4.3.1 Background 

Possibly the most rigorous investigation of multi-seam completion technology for 

coalbed methane was performed at the Rock Creek Field Research Site, and at 

other research sites in the Warrior Basin. The description of GRI’s Rock Creek 

Project is as follows: 

“The Multiple Coal Seam Project is a multi-year, joint venture investigating the 

combination of drilling, completion, stimulation, and production parameters required 

for the economic production of methane from shallow, multiple coal seams.” 

R&D work at Rock Creek on multiple completions technology was, in general, 

successful. However, investigations of the application and performance of this 

technology clearly showed that additional technical issues remain to be solved. 
80

4.3.2 Multi-Seam Completion Analysis 

Subsequent to the research work at the Rock Creek Multiple Coal Seam 

Completion Project, a detailed investigation of underperforming multi-seam 

completed CBM wells was undertaken in several additional areas of the Warrior 

Basin by multiple CBM technical service firms. 

A series of diagnostic tools were used to identify the performance of and 

problems with multi-seam completion technology in these wells, including: 

• A wireline conveyed downhole camera to identify well-specific problems 

involving plugging and non-stimulation of coal intervals; 

• Production logging involving the use of both 1 inch and 3 inch outside 

diameter (OD) tools for determining productive zones; 

• A zone isolation tool (a multiple-packer assembly) to secure accurate 

contribution of gas flow from each zone; and 

• A series of “tank tests” to provide information required for pressure-transient 

analysis. 

The overall findings from this investigation of multi-seam completion practices in 

the Warrior Basin were as follows: 

• Untreated coal zones/seams. Camera surveys, confirmed by subsequent 

flow tests, showed that a significant number of well perforations did not have 

evidence of abrasion or sand from the hydraulic fracture. In the Hendrix # 

3510 test well, 29 percent of the 32 perforation sets in the upper zone were 

not abraded, and 64 percent of the 22 perforation sets in the lower zone were 

not abraded, as shown in Figure 4-5. Camera inspection of the Soterra 9-7 

#1 well indicated no evidence of perforation abrasion, and production testing 

confirmed no fluid flow from two of the thickest coal intervals in the well 

(Figure 4-6). 
81

Figure 4-5. Percentage Distribution of Abraded Perforation Sets within Treatment 

Intervals, Hendrix Study Area Wells. 
82

Figure 4-6. Downhole Camera Observations at the Soterra 9-7 #1 Well. 

• Perforation plugging. Camera surveys showed that perforation plugging (with 

mineralized scale, coal particles and other unidentified substances) appear to 

be a common problem. In the Hendrix # 3510 test well, plugging was found 
83

present within six of the seven sets of perforations examined in the wellbore 

by the camera survey. 

• Cement damage. The investigation identified considerable volume of cement 

“lost in high permeability, naturally fractured wells, likely causing significant 

reservoir damage.” In the Soterra 9-7 #1 well, the evaluation of the 

cementing operation indicated that the Cobb seam and portions of the Gwin 

and Pratt coal seams were so damaged during the cementing operation as to 

preclude gas flow and remediation. 

• Horizontal fractures in shallow coals. The analysis of a series of five shallow 

1,100 to 1,200 wells (including the Oak Grove #681 well, shown in 

Figure 4-7), indicated that a marginally productive top coal seam accepted 

almost all of the treatment during the initial stimulation, leaving the deeper, 

main coal zones unstimulated. 

This research-based well performance investigation in the Warrior Basin provided 

important information for improving the application of multi-seam well completion 

technology in other CBM basins. 

The current application of multi-seam technology in the San Juan, Raton and 

Unita CBM basins, along with its applicability and relevance to the Powder River 

Basin, are provided in Appendix A. The data and information on the application of 

multi-seam technology in these other basins were assembled from state files and 

company records. 
84

Figure 4-7. Downhole Camera Observations, Oak Grove #681 Study Well. 
85

SECTION 5. BENEFITS OF MULTI-SEAM COMPLETION TECHNOLOGY IN THE 

POWDER RIVER BASIN 

5.1 Summary 

The potential benefits of adapting and successfully applying multi-seam 

completion (MSC) technology in the Powder River Basin are numerous. First is the 

access this technology would provide to the vast CBM resource residing in thinner 

coal seams. Second is the improved economics that MSC technology would bring to 

the CBM play. Third is the increased royalty and severance tax revenues that would 

accrue to Montana, Wyoming, and the federal government. Fourth, and equal in 

importance, is the potential reduction in environmental impact that would result from 

producing this vast CBM resource with fewer wells. 

5.2 Increased Natural Gas Resources 

Multi-seam completion technology provides economic and physical access to 

previously bypassed thin (< 20 ft) coal seams. Successful application of this 

technology would increase the accessible coalbed methane gas in-place to 

75 Tcf and raise the technically recoverable CBM resource in this basin to 50 Tcf1

, 

as shown in Figure 5-1. Table 5-1 provides details on the coal and coalbed methane 

in-place as well as the technically recoverable coalbed methane resource in the 

Powder River Basin, by basin partition. 

The application of this technology is particularly relevant to the coalbed methane 

resource in the Montana portion of the Powder River Basin, an area dominated by 

thin, marginal coals. With MSC technology, the accessible CBM resource in-place in 

Montana (in Basin Partitions #9, #10 and #13) is nearly 6 Tcf, with over 5 Tcf being 

technically recoverable. Figure 5-2 provides an outline map of the thirteen partitions 

in the Powder River Basin. 

1. Produced water (from dewatering operations) volumes are forecast to be commensurate with natural gas 

production levels 
86

Figure 5-1. Gas-in-Place and Technically Recoverable CBM Resource, Powder 

River Basin 
87

Table 5-1. Coal and Coalbed Methane Resources of the Powder River 

Basin, by Basin Partition. 

Coal Resource 

Coalbed Methane 

Gas-in-Place 

Technically Recoverable 

Resources 

Basin Partitions (Btons) (Bcf) (Bcf) 

1 20 1,630 1,440 

2 51 2,710 2,120 

3 84 6,460 3,580 

4 83 4,360 3,470 

5 311 25,860 15,650 

6 99 9,440 5,340 

7 69 6,340 3,570 

8 177 9,120 6,870 

11 43 2,480 2,050 

12 4 330 150 

Wyoming 

Sub-Total 941 68,730 44,240 

9 53 2,680 2,400 

10 39 1,490 1,330 

13 48 1,720 1,540 

Montana 

Sub-Total 140 5,890 5,270 

Totals 1081 74,620 49,510 

Source: DOE/Advanced Resources International PRB CBM data base, 2003. 
88

Figure 5-2. Powder River Basin CBM Partitions (MSC study). 
89

5.3 Larger Economically Recoverable Resource 

Multi-seam completion technology can also help to increase the size of the 

economically recoverable coalbed methane resource in the Powder River Basin. 

Using a $3.50/Mcf Henry Hub price for natural gas and a basis differential declining 

from $1.80/Mcf toward historical norms of $0.80/Mcf, labeled as Scenario #2 in this 

study, more than 38 Tcf of coalbed methane is economically recoverable from the 

Powder River Basin. This includes both previously bypassed thin coal seams, as 

well as marginally thick coal seams that are uneconomic to develop with currently 

used single-seam technology. 

Table 5-2 presents the economically recoverable CBM resource for Wyoming and 

Montana, as well as the number of CBM wells expected to be drilled, by mineral 

ownership based on data provided in Wyoming’s Draft EIS for the Powder River 

Basin. 

Table 5-2. Economically Recoverable CBM by Mineral Ownership 

Economically Recoverable CBM 

(Bcf) 

Mineral Ownership* WY MT Total 

Number of CBM 

Wells Drilled 

Federal 22,610 820 23,430 40,580 

State 2,590 100 2,690 4,660 

Private 11,860 430 12,290 21,290 

Total 37,060 1,350 38,410 66,530 

Assumes Scenario #2 economics of $3.50/Mcf for natural gas at Henry Hub and a declining 

basis differential toward historic norms. 

* Based on simplified methodology 
90

5.4 Increased State and Federal Revenues 

The larger economically recoverable CBM resource, due to multi-seam 

technology, will provide significantly higher state, federal and private revenues from 

royalty payments, ad valorem taxes, and severance taxes. In addition, developing 

this natural gas resource will inject billions of dollars of additional capital 

expenditures into the economies of Wyoming and Montana, increasing jobs and 

public infrastructure. 

Royalty payments would provide $10,450 million of revenue, with $5,540 million 

from federally owned lands, $850 million from state-owned lands, and $4,060 million 

from CBM leases on private lands. The states of Montana and Wyoming would 

receive half of the royalty income from leases on federal lands, raising the royalty 

income to the states to $3,620 million from CBM development in the Powder River 

Basin. Ad valorem and severance taxes would add another $7,400 million of state 

and local revenues. 

Finally, CBM development would provide additional stimulus to state and local 

economies. Over the life of the CBM play, an estimated $10.8 billion in capital 

expenditures (based on ARI’s cost model) would be injected in the basin, providing 

jobs, infrastructure, and other commerce. Table 5-3 summarizes the revenue 

benefits that would result from successful development and application of MSC 

technology in the Powder River Basin for Wyoming and Montana. 

Table 5-3. State and Federal Revenues From CBM Development (PRB). 

Royalty Revenues (Millions) 

Ad Valorem and Severance 

Tax Revenues (Millions) 

Mineral Ownership WY MT Total WY MT Total 

Federal $5,342 $194 $5,536 $4,390 $123 $4,513

State $819 $30 $849 $504 $15 $519 

Private $3,920 $146 $4,066 $2,303 $65 $2,368

Total $10,081 $370 $10,451 $7,197 $203 $ 7,400
91

5.5 Economic Sensitivity 

The potential benefits of multi-seam well completion technology was examined 

for two economic scenarios, each assuming a $3.50 per Mcf natural gas price at the 

Henry Hub. In Economic Scenario #1, the basis differential is assumed to remain 

high, at $1.80 per Mcf. This scenario assumes that growth in CBM and other natural 

gas production in the region maintains an excess of gas supply over pipeline 

takeaway capacity. In Economic Scenario #2, the basis differential is assumed to 

decline from $1.80 per Mcf down to $0.80 per Mcf over a period of three years. This 

scenario assumes that the high basis differential common to the PRB during the past 

several years returns to historical norms as new natural gas pipelines are 

completed, enabling the produced CBM to reach high value markets. 

• Under Scenario #1, the economically recoverable CBM resource1 is 24.3 Tcf, 

less than half of the 49.5 Tcf of technically recoverable resource. 

• Under Scenario #2, the economically recoverable CBM resource1 is 38.4 Tcf, 

over three-quarters of the technically recoverable CBM resource. 

The first insight from this economic sensitivity analysis is that reducing the current 

high basis differential would enable over 14 Tcf of additional coalbed methane to 

become economic to develop. 

A second important insight is that further economic development of the Montana 

coalbed methane resource will hinge greatly on reducing the current high basis 

differential, thus improving the netback wellhead gas price for this portion of the 

basin. 

Figure 5-3 and Table 5-4 show the economically recoverable resource for the 

constant basis differential (Scenario #1) situation, and the declining basis differential 

(Scenario #2) situation. 

1. Produced water (from dewatering operations) volumes are forecast to be commensurate with natural gas 

production levels 
92

Table 5-4. Economically Recoverable CBM Resources for 

Scenarios #1 and #2. 

Scenario #1 Scenario #2 

(Tcf) 

Wyoming 24.3 37.1 

Montana 0.0 1.3 

Total 24.3 38.4 

5.6 Reduced Environmental Impacts 

Multi-seam well completion technology , would significantly reduce the required 

number of CBM wells by enabling a single well to jointly produce several coal 

seams, and thus reduce the impact of CBM drilling in the Powder River Basin. 

Assuming 16.9 Tcf of CBM is economically recoverable with the single-seam well 

completion technology practiced today (as set forth in Figure 5-4 for Scenario #2), 

recovering this resource will require the drilling of 40,320 single-seam CBM wells. 

With MSC technology, 11,000 fewer wells will be needed to recover this same 

volume of CBM resource, a reduction of 27 percent. Table 5-5 shows the reduction 

in the number of wells drilled to recover comparable CBM resources by using MSC 

technology instead of single-seam technology. 
93

 Recoverable CBM Resources, Two Economic Scenarios, Powder River Basin 
94
95

Table 5-5. Number of Wells Required to Produce CBM Resources in the PRB, Two 

Alternative Well Completion Technologies. 

Difference Due to 

MSC Technology 

Well Completion 

Technology 

Economically 

Recoverable Resource 

Base (Tcf) 

Reserves/ Well 

(MMcf) 

No. of Wells 

Required 

Total 

Wells % 

Single-Seam Wells 16.9 419 40,320 - - 

Multi-Seam Wells* 16.9 577 29,260 (11,060) (27%) 

* calc. based on single-seam economically recoverable volume of gas 

5.7 Benefits of MSC Technology 

There are many valid reasons for developing and applying MSC technology 

appropriate to the coals of the Powder River Basin. The most compelling reason is 

that it would significantly increase the economically recoverable coalbed methane 

resource in this basin. (And, as discussed above in 5.5 Reduced Environmental 

Impacts, it would accomplish this with significantly fewer wells.) Using a $3.50 per 

Mcf natural gas price at the Henry Hub, the results are as follows: 

• Under Economic Scenario #1, MSC technology would provide 24.3 Tcf of 

economically recoverable coalbed methane resource. With continued use of 

single-seam technology, only 2.7 Tcf would be economically recoverable, a 

difference of 21.6 Tcf. 

• Under Economic Scenario #2, MSC technology would provide 38.4 Tcf of 

economically recoverable coalbed methane resource. With continued use of 

single seam technology, only 16.9 Tcf would be economically recoverable, a 

difference of 21.4 Tcf. 

Figure 5-4 illustrates the impact of that MSC technology would have on 

economically recoverable CBM resources from the Powder River Basin. Under the 

two economic scenarios, Tables 5-6 and 5-7 provide additional state level data on 

the impacts of MSC technology. 
96

Table 5-6. Distribution of Economic CBM Resources Under Scenario #1. 

SSC Technology MSC Technology Difference 

(Tcf) (Tcf) (Tcf) 

Wyoming 2.7 24.3 21.6 

Montana 0.0 0.0 - 

Total 2.7 24.3 21.6 

Table 5-7. Distribution of Economic CBM Resources Under Scenario #2. 

 

SSC Technology MSC Technology Difference 

(Tcf) (Tcf) (Tcf) 

Wyoming 16.9 37.1 20.2 

Montana 0 1.3 1.3 

Total 16.9 38.4 21.5 

5.8 Detailed Benefits of Using MSC Technology 

Successful MSC technology would beneficially impact CBM development in the 

Powder River Basin in many ways, as illustrated by the following examples. These 

four examples cover many of the geologic settings encountered in the PRB, 

including the central portion of the basin where thin seams coexist with major thick 

coals, as well as the northern and western basin flanks where much of the coal is 

deposited primarily in thin seams. 
97

5.8.1 Example #1 

Currently uneconomic, marginally thick coals are completed along with a series of 

thin coals to make an economic well. 

Under current practices, a single seam CBM well targeting the 25-foot Canyon 

coal seam in T54N R80W would recover 0.21 Bcf of gas and with this low gas 

recovery, the well is sub-economic. With MSC technology, the Canyon coal seam in 

this township can be completed with three additional thin seams (16 ft., 19 ft., and 15 

ft.) that would have been bypassed under current practices. The result is an 

economic CBM well that would recover 0.57 Bcf. In addition, the packaging of four 

coal seams in one well significantly lowers finding and development (F&D) costs in 

this township from an uneconomic $0.67/Mcf to an economic $0.27/Mcf as 

summarized for Example #1 in Table 5-8 below. 

Table 5-8. Multi Seam Example #1 – Marginally Economic Thick Coal Seam Is 

Completed with Thin Seams to Make an Economic CBM Well. 

Current Single-Seam Technology 

Proposed Multi-Seam 

Technology 

CAPEX/Well $139,950 $154,960 

EUR/Well 208 MMcf 566 MMcf 

Water/Well 193 Mbw 368 Mbw 

Water:Gas Ratio 0.93 Bw/Mcf 0.65 Bw/Mcf 

F&D Cost $0.67 per Mcf $0.27 per Mcf 

5.8.2 Example #2 

Several thin coal seams bypassed under present practices are completed, along 

with a currently economic seam to increase reserves per well while adding relatively 

little to capital costs. 

A single seam CBM well targeting the 50-foot Anderson coal seam in T45N 

R77W would recover 0.53 Bcf of gas and would be economic under present 

wellhead price conditions. However, several nearby thin seams are not economic. 
98

With MSC technology, one shallower 19 foot coal seam and two deeper coal seams 

(19 ft. and 10 ft.) can be completed with the economic Anderson seam, increasing 

well reserves to nearly 1.0 Bcf. The additional recovery from the thin seams offset 

the modest increase in drilling and completion costs, lowering F&D costs to $0.17 

per Mcf as summarized in Table 5-9. 

Table 5-9. Multi Seam Example #2 – Thin Seams Are Completed with an Economic 

Thick Coal Seam to Increase Well Reserves. 

Current Single-Seam 

Technology 

Proposed Multi-Seam 

Technology 

CAPEX/Well $130,470 $167,960 

EUR/Well 531 MMcf 967 MMcf 

Water/Well 161 Mbw 449 Mbw 

Water:Gas Ratio 0.30 Bw/Mcf 0.46 Bw/Mcf 

F&D Cost $0.25 per Mcf $0.17 per Mcf 

 

5.8.3 Example #3 

Two (or more) economic seams are completed with the same well to reduce 

capital expenditures while cutting the required number of CBM wells in half (or less). 

The Anderson (60 ft.) and the Canyon (60 ft.) coal seams in T49N R73W both 

provide economic CBM wells even when they are completed separately. A well 

producing from each of these seams will recover over 0.3 Bcf. With MSC 

technology, the Anderson and Canyon seams are completed in a single well, along 

with two sub-economic thick seams (both 25 ft.), increasing reserve per well, 

reducing the number of required CBM wells, and reducing total capital expenditures 

by $86,500, as summarized in Table 5-10. 
99

Table 5-10. Multi Seam Example #3—Multiple Economic Coal Seams Are Completed 

in a Single Well to Reduce Capital Expenditures and Surface Disturbance. 

Current Single-Seam 

Technology 

Proposed Multi-Seam 

Technology 

CAPEX/Well $227,720* $141,180 

EUR/Well 667 MMcf* 834 MMcf 

Water/Well 623 Mbw 817 Mbw 

Water:Gas Ratio 0.93 Bw/Mcf 0.98 Bw/Mcf 

F&D Cost $0.34 per Mcf $0.17 per Mcf 

*Two single-seam well costs and reserves are combined for this table. 

5.8.4 Example #4 

A basin area containing only thin coals is made economic by completing up to 

four seams in one well. This case is of particular importance in on the western side 

of the Powder River CBM play and in Montana where thick (>20 ft.) coals are much 

less common. 

Under current practices, coals less than 20 feet thick are generally bypassed. As 

development using single-seam completion technology progresses, the likelihood 

that operators will return to an area to complete such seams in individual wells is in 

doubt. With MSC technology, coalbed gas from these bypassed townships can be 

economically produced. For example, T51N R81W contains several deep thin coal 

seams that would be bypassed under current conditions. With MSC technology, four 

seams (three 18 ft. coal seams and one 11 ft. seam) are completed in a single well 

that will recover over 0.68 Bcf, as summarized in Table 5-11. 
100

Table 5-11. Multi Seam Example #4 — An Uneconomic Township Is Made Economic 

Using MSC Technology. 

Current Single-Seam 

Technology 

Proposed Multi-Seam 

Technology 

CAPEX/Well N/A $232,380 

EUR/Well N/A 681 MMcf 

Water/Well N/A 854 Mbw 

Water:Gas Ratio N/A 1.25 Bw/Mcf 

F&D Cost N/A $0.34 per Mcf 
101

REFERENCES 

1. U.S. DOE. 2002. Powder River Basin Coalbed Methane Development 

and Produced Water Management Study. DOE/NETL-2003/1184. 

Springfield, VA: National Technical Information Service. 

2. Wyoming Coalbed Methane Production from the Powder River Basin. 

2003. Wyoming Oil and Gas Conservation Commission online database. 

http://wogcc.state.wy.us/ 

3. Taurus Exploration, Advanced Resources International, and Gas 

Research Institute. 1994. “Effective Completions for Shallow Coal Seams,” 

Topical Report. GRI-93/0366. Government sponsored? City, State: 

Publisher/office where filed. 

4. Taurus Exploration, Advanced Resources International, and Gas 

Research Institute. 1996. “Coalbed Methane Production 

Improvement/Recompletion Project in the Warrior Basin,” Final Report GRI95/0034.. Government sponsored? City, State: Publisher/office where filed. 

5. “Rocky Mountain Production.” 2003. IHS Energy, PI/Dwights Plus, 

Volume 13, Issue 2. 

6. “Rocky Mountain Well,” 2003. IHS Energy, PI/Dwights Plus, Volume 

13, Issue 2. 
A-1

APPENDIX A 

ASSESSMENT OF MULTI-SEAM WELL COMPLETION PRACTICES: 

SAN JUAN, RATON, AND UINTA CBM BASINS 

1. SAN JUAN BASIN 

Coalbed Methane Reservoir Setting. The coals in the San Juan Basin are 

contained in the Fruitland Formation at depths of 2,500 to 3,500 feet. The coalbearing interval is typically 200 to 300 feet, with maximum coal development 

occurring at the base of the section. Net coal thickness can reach 80 to 100 feet. 

The coal package consists of 5 to 10 individual seams with individual coal thickness 

typically 10 to 20 feet, as shown for the Amoco Production Co. #2 Short Lyle Gas 

Unit A well, shown in Figure A-1. 

The Fruitland section rarely includes sandstones, and when present, the 

sandstones are typically tight. Shales are generally stable and do not interfere with 

completion or production operations. 

Well Completion Practices. Two distinct coalbed methane well completion 

practices are used in the San Juan Basin for coalbed methane: (1) cased-hole well 

completions with single-stage stimulation; and, (2) open-hole well completions with 

dynamic cavitation. These two practices and their relevance to the Powder River 

CBM play are briefly discussed below. 

Cased-Hole Completion, Single-Stage Stimulation. Casing is cemented in place 

over the coal section. Every coal seam in the coal interval is perforated. The entire 

coal section is hydraulically stimulated using a single-stage stimulation. The 

stimulation consists typically of 90,000 gallons of a high viscosity gel, and 200,000 

pounds of sand. 

Figure A-1 provides an example of a typical San Juan Basin cased-hole well 

completion, showing the coal section and the well completion and stimulation 

practices used to connect multiple coals to a single well. 
A-2

Relevance to the PRB. The San Juan Basin stimulations are designed for 

maximum vertical growth, to connect as many coal seams to the well bore as 

possible. There is little risk from communicating with underlying or overlying water 

bearing formations, as the Fruitland formation rarely includes porous and permeable 

sandstones. 

In contrast to the San Juan Basin, porous and permeable sandstones are 

typically encountered in coal sections of the Powder River Basin. A stimulation 

design for significant vertical growth would unavoidably communicate with aquifers 

in the stimulated interval and would delay or preclude dewatering of the coal seams. 

The multi-seam stimulation method used in the San Juan Basin is not applicable to 

the PRB. 

Open-Hole Completion, Dynamic Cavitation. Casing is set and cemented inplace at the top of the coal interval. The coal interval is drilled out and left open. 

The well is stimulated using the dynamic cavitation process where air and water 

are injected into the well under high pressure. The pressure is rapidly released, 

causing the open-hole section to surge large volumes of gas, water and coal. The 

process is repeated until maximum flow rates are achieved. 

Figure A-2 provides an example of a typical San Juan Basin open-hole well 

completion, showing the coal section and the completion practice used to connect 

the multiple coals in this well. 

Relevance to the PRB. Although open-hole cavitation has been attempted in 

several coal basins in the U.S., it has only been successful in the San Juan Basin 

fairway. A unique set of favorable reservoir properties is required to achieve 

successful cavitation. 

The reservoir properties necessary for cavitation are not present in the PRB. The 

shales and clays associated with coals in the PRB are unstable and cannot be 

included in an open-hole seam, precluding the application of this multi-seam 

completion approach in the PRB. 
A-3

 

Figure A-1 Cased Hole Completion, Single-Stage Stimulation, 

San Juan Basin CBM Well. 
A-4

Figure A-2. Open-Hole Completion, Dynamic Cavitation, San Juan Basin CBM Well. 
A-5

2. RATON BASIN 

Coalbed Methane Reservoir Setting. Coal development in the Raton and 

underlying Vermejo formations is at drilling depths of 1,500 to 2,500 feet. Coal 

seams in the Raton Formation are typically thin, with individual seam thickness of 2 

to 4 feet. Coals as thick as 10 feet are not uncommon, however they tend to be 

lenticular in nature. Average net coal thickness varies between 20 to 40 feet, with an 

occasional coal package of over 100 feet. The coal development in the Vermejo 

Formation is similar to the Raton Formation coal seams. 

Figure A-3 provides a well log and completion summary for the Evergreen 

Operating Corp. #41-16 Crossbow well in the Raton Basin. 

Well Completion Practices. The primary CBM well completion practice in the 

Raton Basin is a cased-hole well with multiple, relatively small hydraulic fractures. 

This well completion practice and its relevance to the Powder River CBM play is 

discussed below. 

Cased-Hole Completion, Multiple Stage Stimulation. The wells are drilled underbalanced to reduce formation damage. A 5.5 inch casing string is cemented in place 

to total well depth. Each coal seam is selectively perforated. 

Single coal seams and small intervals containing multiple coal seams are 

hydraulically stimulated. A single well will have between three and six stimulation 

stages, depending on the extent of coal development. 

The stimulation begins with a small acid break down. This is followed with a 

larger nitrogen foam breakdown and sand. Cross-linked gel and sand is used in the 

last stimulation stage. The typical final stimulation stage consists of 200 to 400 

barrels of gel and 20,000 to 40,000 pounds of sand. 

Figure A-3 provides an example of a typical Raton Basin cased-hole completion, 

showing the coal section and the well completion and stimulation practices used to 

connect multiple coals to a single well. 
A-6

Figure A-3. Cased Hole Completion, Multiple-Stage, 

Small Interval Stimulation, Raton Basin CBM Well. 
A-7

Relevance to the PRB. The emphasis in the Raton Basin is on low cost, 

multiple seam stimulations. This approach may provide insight for an appropriate 

well completion and stimulation technology for the Powder River Basin. 

A major question is whether the stimulations designed for thin, higher rank coal 

seams would be applicable to the thicker, low rank coals in the PRB. 

In addition, the stimulation fluids used in the Raton Basin might not be 

appropriate for use in the Powder River Basin. The use of certain additives could 

possibly be restricted or prohibited in coal seams that are aquifers or in close 

proximity to sand aquifers. 

In summary, it is very probable that significant modifications would be required to 

transfer Raton Basin well completion and stimulation practices to the Powder River 

Basin. 
A-8

3. UINTA BASIN 

 Coalbed Methane Reservoir Setting. Depth of the Ferron coal varies 

between 1,200 to 3,400 feet with 2,400 feet being average for current CBM 

development wells. The Ferron coal sequence typically has three to six coals over a 

150 to 200 foot interval. Single coal seam thickness is rarely greater than 10 feet. 

Net coal thickness can vary between 5 to 35 feet with 24 feet being an average net 

coal thickness. 

Figure A-4 provides a well log and completion summary for the Phillips Petroleum 

Company # 7-741 USA well in the Uinta Basin. 

Well Completion Practices. The primary CBM well completion practice in the 

Uinta Basin is a cased-hole well with one or two large vertical interval stimulations. 

Cased-Hole Completion, Large Vertical Interval Stimulations. The CBM wells are 

drilled with air to total depth, with a 5.5 inch casing string cemented in place across 

the coal interval. Each coal seam is individually perforated. 

The wells are hydraulically stimulated using a high viscosity, cross-linked gel. A 

single well will typically have one or two such treatments across a relatively large 

formation interval. Hydraulic fracture volumes are typically 50,000 gallons of gel 

and 50,000 to 90,000 pounds of sand per treatment. 

Figure A-4 provides an example of a typical Uinta Basin cased-hole completion, 

showing the coal section, and the well completion and stimulation practices used to 

connect multiple coals to a single well. 

Relevance to the PRB. The large interval stimulations used in the Uinta Basin 

are designed for vertical growth, to effectively connect the entire coal section to the 

well bore. Although, the Ferron coal sequence sometimes includes thin interbedded 

sandstones, the sand reservoirs are not thought to contribute significantly to water 

production. 
A-9

Figure A-4. Cased Hole Completion, Multiple-Stage Large Interval 

Stimulation, Uinta Basin CBM Well. 
A-10

Water-bearing sand aquifers are commonly interbedded with target zones within 

the PRB coal intervals. The use of a stimulation that is designed for vertical growth 

would unavoidably connect these aquifers and coal seams. The inclusion of 

stimulated aquifers would result in excessive water production, hampering or 

precluding dewatering of the coal seams. 

The Uinta Basin multiple-seam well completion and stimulation practices are not 

an appropriate model for the PRB.