U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-158-02 (Supercedes USGS Fact Sheet FS-110-01)

February 2003 Printed on recycled paper

Printed on recycled paper

Coal-Bed Gas Provinces of the

Rocky Mountain Region

The Rocky Mountain region contains several sedimentary provinces with extensive coal deposits and significant accumulations of 

coal-bed gas. This summary includes coal-bed gas resources in the 

Powder River Basin (Wyoming and Montana), Wind River Basin 

(Wyoming), Southwest Wyoming (Greater Green River Basin of 

Wyoming, Colorado, and Utah), Uinta-Piceance Basin (Colorado and 

Utah), Raton Basin (Colorado and New Mexico), and San Juan Basin 

(Colorado and New Mexico). Other provinces in the Rocky Mountain region may contain significant coal-bed gas resources, but these 

resource estimates are not available at this time.

What is Coal-Bed Gas?

Coal-bed gas is natural gas associated with, and sourced by, coal. 

Coal-bed gas is mainly composed of methane with variable amounts 

of ethane, nitrogen, and carbon dioxide. Methane can be generated 

by biogenic (microbial) or thermogenic (thermal) processes. Biogenic methane is formed when microbes act upon coals very near the 

surface, whereas thermogenic methane is formed as the temperature 

of a coal bed increases with increasing depth of burial. Generally, the 

amount of thermogenic gas in a coal increases with higher temperatures. Methane gas occurs as gas adsorbed onto coal surfaces, as 

free gas in fractures, cleats, or other porosity, and as gas dissolved 

in ground water within the coal beds. The amount of methane gas 

generated in a particular coal bed depends upon the depth of burial 

and related pressure, the temperature to which a coal has been raised, 

coal thickness, and coal composition. To produce coal-bed gas, 

the water in the coal must be removed by pumping, allowing the 

pressure in the coal to drop sufficiently for the gas to flow. Water 

produced during the coal-bed methane operation varies in quantity 

and quality among, and within, coal-bed methane plays. In some 

plays, the produced water may be sufficiently fresh to discharge onto 

the surface, whereas in other plays the water may require special 

National Assessment of Oil and Gas Fact Sheet

Coal-Bed Gas Resources of the Rocky Mountain Region

roduction of natural gas 

associated with coal beds 

accounts for about 7 percent of 

the total natural gas produced 

annually in the United States. 

Several important U.S. coalbed gas-producing areas are 

in the Rocky Mountain region, 

where extensive shallow coal 

beds have produced or have 

the potential to produce coalbed gas (fig. 1). We summarize 

the technically recoverable 

coal-bed gas resources of six 

geologic provinces in the 

Rocky Mountain region herein.

treatment and (or) reinjection. The necessity of proper disposal of 

produced water increases the technological complexity of coal-bed 

gas production and results in water production being a governing 

factor in the production process.

How is Coal-Bed Gas Recovered?

Once a coal bed is known to contain recoverable coal-bed gas 

through a program of testing and analysis of exploratory wells, other 

wells are drilled into the coal to produce the gas (fig. 2). Each well is 

fitted with a pump to first remove water from the coal, a process that 

may take months or even years to complete. Some wells may require 

artificial fracturing to induce sufficient permeability for the water and 

gas to move out of the coal. As the coal is de-watered, methane gas 

begins to be produced with the water, and the gas is separated from 

the water at the surface. A coal bed may extend beneath a large area 

of a province, and because a single well only recovers the gas from a 

small part of the coal bed, many hundreds to thousands of wells may 

be required to recover the gas.

Assessment of Coal-Bed Gas

The U.S. Geological Survey National Oil and Gas Resource 

Assessment Team (1995) and Gautier and others (1996) defined 

and assessed the major coal-bed gas accumulations of the United 

States. The USGS has an ongoing effort to reassess the coal-bed gas 

resources of the United States. The Powder River Basin, UintaPiceance Basin, San Juan Basin, and SW Wyoming provinces were 

Figure 1. Selected coal-bed gas 

provinces of the Rocky Mountain 

region assessed for this study.

P

Southwestern

Wyoming

Wind River Basin

Powder River Basin

Uinta-Piceance Basin

San Juan Basin

Raton Basin
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reassessed most recently in 2002. In the six geologic provinces 

assessed for this study, the assessment at present indicates that about 

44.5 trillion cubic feet (TCF) of technically recoverable coal-bed gas 

(mean estimate) exists (table 1). The Powder River Basin is estimated 

to contain nearly one third (14.2 TCF at the mean) of the undiscovered 

coal-bed gas resource. The San Juan Basin, where coal-bed gas has 

been produced for 20 years, is estimated to contain about 54% (24.2 

TCF) of undiscovered coal-bed gas at the mean. In a national perspective, coal-bed gas production accounts for about 1.3 TCFG of the 18.5 

TCFG of total natural gas produced annually in the U.S. Although the 

production of coal-bed gas is minor compared to natural gas production from conventional oil and gas fields, coal-bed gas production is 

important regionally, as in provinces of the Rocky Mountain region. 

Assessment results can be found at energy.cr.usgs.gov/oilgas/noga

Summary

A significant portion of the undiscovered coal-bed gas resource 

of the U.S. occurs in Rocky Mountain provinces. If the demand 

for natural gas increases significantly through the next few decades, 

as expected, coal-bed gas will continue to be an important regional 

source of natural gas.

References Cited

Gautier, D.L., Dolton, G.L., Takahashi, K.I., and Varnes, K.L., 1996, 1995 

National assessment of United States oil and gas resources—

Results, methodology, and supporting data: U.S. Geological Survey 

Digital Data Series DDS-30, Version 2, one CD-ROM.

U.S. Geological Survey National Oil and Gas Resource Assessment 

Team, 1995, 1995 National assessment of United States oil and gas 

resources: U.S. Geological Survey Circular 1118, 20 p.

Figure 2. Diagram illustrating the production of water (blue) and gas (white) 

from a coal bed (black) in a typical coal-bed methane well. Other rock types 

are shown in yellow. Coal-bed gas and water are separated at the surface.

Table 1. Coal-bed gas resources of selected Rocky Mountain provinces. 

The year signifies the date of the latest USGS assessment of each 

province.

[TCFG, trillion cubic feet of gas. F95 represents a 95 percent chance of at least the 

amount of resource tabulated; F5 represents a 5 percent chance of at least the amount of 

resource tabulated] For More Information on Coal-Bed Methane:

National Assessment of Oil and Gas Project

C.J. Schenk (schenk@usgs.gov)

U.S. coal-bed gas resources

V.F. Nuccio (vnuccio@usgs.gov)

Powder River Basin, Raton Basin

R.M. Flores (rflores@usgs.gov)

Wind River Basin, SW Wyoming, Uinta-Piceance Basin

R.C. Johnson (rcjohnson@usgs.gov)

S.B. Roberts (sroberts@usgs.gov)

T.M. Finn (finn@usgs.gov)

San Juan Basin

J. Ridgley (ridgley@usgs.gov)