DATA SERIES 683

U.S. GEOLOGICAL SURVEY PLATE 4 0F 5

Coalbed Gas Assessment Unit Age Basin Depositional Environment Formation Depths Gas Content Geochemistry Rank Resources Thickness Water Issues

Mesaverde Coalbed Gas AUs (Johnson and 

others, 2005; Finn and others, 2005).

Thumbnail graphic showing the portion of the Mesaverde Coalbed Gas 

AUs that lie within the WLCI (67 percent of the assessed area). Late Cretaceous

Coals were deposited in lower coastal plain 

depositional settings (Johnson and others, 

2005; Finn and others, 2005).

For both the Mesaverde Coalbed Gas Assessment Unit (AU) 

(50370581) in the Mesaverde Total Petroleum System (TPS), and the 

hypothetical Mesaverde Coalbed Gas AU (50370681) in the 

Mesaverde-Lance-Fort Union Composite TPS, the AU areas define 

where significant coal is at depths of less than 6,000 ft (Johnson and 

others, 2005; Finn and others, 2005). For the Mesaverde TPS, the 

stratigraphically highest coals in the Mesaverde Group are in the 

Almond Formation (Johnson and others, 2005). In the MesaverdeLance-Fort Union Composite TPS, the AU defines coals in the Rock 

Springs Formation. Commercial production rarely extends to depths 

greater than 6,000 ft (Finn and others, 2005).

Coals in the Mesaverde Coalbed Gas AU 

(50370581) in the Mesaverde TPS, contain as 

much as 540 standard cubic feet per ton (scf/ton; 

Tyler and others, 1995).

Glass and Jones (1991) reported that as-received analyses of coalbeds 

in the Green River Coal Field indicate moisture values averaging 20.5 

percent, ash averaging 8.8 percent, total sulfur averages of 0.5 

percent, and average heating content of 9,480 Btu/lb.

Almond Formation coals are subbituminous 

(Glass, 1977). See also, plate 2, Green River Coal 

Field.

The 2002 assessment of the U.S. Geological Survey 

(USGS) estimated a mean volume of about 248.7 billion 

cubic feet (BCF) of undiscovered, technically 

recoverable natural gas in the Mesaverde Coalbed Gas 

AU east of the pinchout of the Lewis Shale (Johnson and 

others, 2005). The hypothetical Mesaverde Coalbed Gas 

AU to the west was given a mean estimate of 27.3 BCFG 

that has potential for additions to reserves over the next 

30 years (Finn and others, 2005).

Glass (1977) reported that in the Rock Springs area, Mesaverde 

coals are in the 500-ft-thick Almond Formation, which marks 

the top of the Mesaverde sequence, and in the 1,400-ft-thick 

Rock Springs Formation near the base of the Mesaverde Group. 

Rock Springs coals reportedly range from 10 to 14 ft thick, but 

4 to 6 ft coals are more common. Almond coals seldom exceed 

8 ft in thickness, but are more numerous. On the east side of 

the Green River Region, Mesaverde Group coals average less 

than 4 ft thick, but locally reach 16 ft. See also, plate 2, Green 

River Coal Field.

Coalbed natural gas (CBNG) production requires extraction of 

large volumes of water from target formations. This may alter 

local aquifers and large hydrologic systems. Previously in 

Wyoming, scientifically defined baseline data of CBNG 

targeted aquifers was outpaced by CBNG production. Being a 

newer CBNG play, springs, streams, and CBNG wells across 

the Atlantic Rim were sampled to quantify regional 

hydrogeology before full scale CBNG production. To 

characterize each water sample, field measurements, chemical 

analysis, and C and Sr isotopic analysis were used. The extent 

to which isotopic data allow predictive modeling of lifespan of 

production can be assessed with ongoing, periodic resampling 

and isotopic analysis of Atlantic Rim co-produced waters 

(McLauglin and others, 2009).

Fort Union Coalbed Gas AUs (Finn and 

others, 2005; Roberts, 2005a)

Thumbnail graphic showing the portion of the Fort Union Coalbed Gas 

AUs that lie within the WLCI (82 percent of the assessed area). Paleocene

Roberts (2005a) described the Fort Union 

Formation as fluvial and alluvial deposition 

coincident in large part with Laramide 

structural development of the basins and 

uplifts that are present within and 

surrounding the Southwestern Wyoming 

Province. Coals were deposited in lower 

coastal plain depositional settings (Finn and 

others, 2005).

The hypothetical Fort Union Coalbed Gas AU (AU50370682) 

encompasses nearly 1.2 million acres in four separate areas around 

the margins of the Mesaverde-Lance-Fort Union Composite TPS 

where significant coal is present in the Fort Union Formation at 

depths of 6,000 ft or less (Finn and others, 2005). In the Lance-Fort 

Union Composite TPS, the Fort Union Coalbed Gas AU 

(AU50370882) is also hypothetical and includes areas where 

coalbeds in the basal 1,000 ft of the Fort Union Formation are 

interpreted to be at depths of less than 6,000 ft (Roberts, 2005a). 

Tyler and others (1995) reported that gas has been 

documented in Fort Union Formation coalbeds in 

the Lance–Fort Union Composite TPS, with 

measured gas contents generally less than 100 

scf/ton (Tyler and others, 1995).

Roberts (2005a) reported that as-received analyses of the upper and 

lower Cherokee coalbeds in the Cherokee coal zone near the top of 

the Fort Union Formation indicate moisture ranging from 15 to 25 

percent, ash yields ranging from 10 to 25 percent, total sulfur ranging 

from 0.5 to 5.0 percent, and heating content ranging from 5,000 to 

9,000 Btu/lb (Glass, 1981, after Smith and others, 1972). See also 

plate 2, Green River Coal Field.

Finn and others (2005) reported ranks of Fort 

Union coals within the Mesaverde-Lance-Fort 

Union Composite TPS are mostly subbituminous 

to high-volatile C bituminous (Tyler and others, 

1995). The apparent rank of Fort Union coal 

within the Lance-Fort Union Composite TPS is 

subbituminous (Roberts, 2005a).

The 2002 assessment of the USGS estimated the 

hypothetical Fort Union Coalbed Gas AU to the west 

was given an estimate of 80.8 BCFG that has potential 

for additions to reserves over the next 30 years (Finn and 

others, 2005). To the east, within the Lance-Fort Union 

Composite TPS, the USGS estimated a mean volume of 

942.5 BCF of undiscovered, technically recoverable 

natural gas in the Fort Union Coalbed Gas AU (Roberts, 

2005a).

Tyler and others (1995) reported individual coal thicknesses of 

as much as 40 ft within the area now included in the Fort Union 

Coalbed Gas AU in the Mesaverde-Lance-Fort Union 

Composite TPS. Finn and others (2005) stated that total coal 

thicknesses within the AU generally average 10 to 60 ft in the 

Mesaverde-Lance-Fort Union Composite TPS. In the LanceFort Union Composite TPS, Roberts (2005a) described Fort 

Union coalbed thickness within the AU ranging from less than 

1 ft to as much as 50 ft, and continuous coalbeds or zones are 

present within 1,000–1,200 ft above the base of the formation 

(lower coal-bearing unit; Tyler and others, 1995). Cumulative 

coal thickness in this lower interval exceeds 80 ft in areas of 

the AU along Cherokee Ridge and the Wamsutter Arch and 

may exceed 100 ft locally (Tyler and McMurry, 1993; Tyler 

and others, 1995; as reported in Roberts, 2005a).

Lance Coalbed Gas AU (hypothetical); 

Roberts, 2005a.

Thumbnail graphic showing the portion of the Lance Coalbed Gas AU 

that lies within the WLCI (65 percent of the assessed area). Late Cretaceous

As the Western Interior Seaway retreated 

from the region during the latest Cretaceous, 

coal-forming environments were in coastal 

plain and fluvial/alluvial depositional 

settings (Roberts, 2005a).

The Lance Coalbed Gas AU includes areas where coalbeds in the 

basal 300–500 ft of the Lance Formation are interpreted to be at 

depths of 6,000 ft or less (Roberts, 2005a).

Roberts (2005a) assumed that, because coalbeds in 

the Lance and Fort Union Formations are of 

similar rank (subbituminous), gas contents might 

also be similar. See Fort Union Coalbed Gas AUs.

Roberts (2005a) reported that coalbeds in this area typically have ash 

averaging about 5 percent, total sulfur contents averaging about 0.7 

percent, and average moisture contents of about 20 percent (Keystone 

Coal Industry Manual, 1999).

Roberts (2005a) reported the apparent rank of 

Lance Formation coal on the southeast flank of the 

Rock Springs uplift is subbituminous B (Keystone 

Coal Industry Manual, 1999).

The hypothetical Lance Coalbed Gas AU, was estimated 

by the USGS at a mean volume of 165 BCF of 

undiscovered, technically recoverable natural gas 

(Roberts, 2005a).

Cumulative coal thickness in the Lance typically is less than 

30–40 ft, with minimum values of less than 10 ft and a 

maximum reported total coal thickness of 85 ft; reported 

thicknesses for individual coalbeds within the AU range from 

less than 1 ft to as much as 13 ft (Law, 1996; as reported in 

Roberts, 2005a).

Wasatch–Green River Coalbed Gas AU 

(hypothetical); Roberts, 2005b.

Thumbnail graphic showing the portion of the Wasatch–Green River 

Coalbed Gas AU that lies within the WLCI (87 percent of the assessed 

area). Paleocene and Eocene

The Wasatch Formation was deposited 

primarily in a fluvial/alluvial depositional 

setting during the latter stages of the 

Laramide Orogeny (Roberts, 2005b).

The Wasatch–Green River Coalbed Gas AU includes areas where 

coalbeds in the main body of the Wasatch Formation, and Red Desert 

and Niland Tongues of the Wasatch Formation, and the Luman 

Tongue of the Green River Formation are present in outcrops and in 

the shallow (less than 2,500 ft) subsurface (Roberts, 2005b).

Coalbed gas wells producing from subbituminous 

coal in the Fort Union Formation in the Powder 

River Basin (PRB) in northeastern Wyoming were 

used as analogs, because no coalbed gas 

production or test data specific to the Wasatch and 

Green River Formations were available. For Fort 

Union Formation coal in the PRB, reported gas 

contents vary from 6 to more than 75 scf/ton and 

are commonly in the range of 20 to 40 scf/ton (for 

example, see Stricker and others, 2000; Boreck 

and Weaver, 1984). It was assumed by Roberts 

(2005b) that because coalbeds in the Wasatch and 

Green River Formations are of similar rank 

(subbituminous C to high-volatile C bituminous), 

gas contents might also be similar.

Roberts (2005b) reported that analyses (as-received) of samples from 

thicker Eocene coalbeds in the Great Divide Basin indicate an 

average moisture content of about 21 percent, an average ash of about 

16 percent, an average total sulfur content of 2.5 percent, and an 

average heat content of about 7,900 Btu/lb (Glass, 1981, after Smith 

and others, 1972). The Vermillion Creek coalbed has an apparent 

rank of high-volatile C bituminous (Hatch, 1987), although 

inconsistent agglomerating characteristics in certain coal samples 

indicate the coal could also be considered as subbituminous (for 

example, see Ellis, 1987). As-received moisture values typically 

range from about 11 to 15 percent, and average, as-received values 

for ash and total sulfur content are 18.2 and 5.6 percent, respectively; 

heat content (moist, mineral-matter-free basis) averages 11,556 Btu/lb 

(Ellis, 1987; Hatch, 1987).

Apparent coal rank varies from subbituminous C 

to B (Pipiringos, 1961; Masursky, 1962; as 

reported in Roberts, 2005b).

Roberts (2005b) reported that the potential for 

significant coalbed gas production from the Wasatch and 

Green River Formations in the near future appears 

limited. The fact that many of the coalbeds are in close 

proximity to outcrops could result in gas leakage, and 

the thin, discontinuous nature of these coalbeds could 

restrict reservoir (and gas) volume. The hypothetical 

Wasatch–Green River Coalbed Gas AU, was assessed in 

2002 when the USGS estimated a mean volume of 64.7 

BCF of undiscovered, technically recoverable natural 

gas.

Most coals average about 7 ft thick however, several beds are 

as thick as 20 ft, and lenticular coalbeds are locally as thick as 

42 ft (Roberts, 2005b).

Frontier-Adaville-Evanston Coalbed Gas 

AU (hypothetical); Kirschbaum and others, 

2004.

Thumbnail graphic showing the portion of the Frontier-AdavilleEvanston Coalbed Gas AU that lies within the WLCI (80 percent of the 

assessed area).

Cretaceous and Tertiary (Kirschbaum and 

others, 2004)

Fossil Basin (Love and 

Christiansen, 1985)

In 2003, the hypothetical Frontier-Adaville-Evanston 

Coalbed Gas AU, was assessed by the USGS to contain 

an estimated mean volume of 361 BCF of undiscovered, 

technically recoverable natural gas (Kirschbaum and 

others, 2004).

Medicine Bow–Ferris–Hanna Coalbed Gas 

AU—Not quantitatively assessed (Dyman 

and others, 2006)

Cretaceous and Tertiary (Dyman and Condon, 

2007)

Dyman and Condon (2007) reported that Glass and Roberts (1980) 

recognized that the most numerous coalbeds are in the upper 12,000 ft 

of the Hanna Formation and in the upper part of the Ferris Formation 

in the northern part of the Hanna Basin. Medicine Bow coals are 

generally restricted to the lower part of the formation (Merewether, 

1971, 1972, 1973; Glass and Roberts, 1980; as reported in Dyman 

and Condon, 2007).

Hanna Formation coals in the Hanna coal field 

north of Hanna, Wyoming, are high-volatile C 

bituminous, according to Glass and Roberts (1980, 

1984). Ferris Formation coals in the Seminoe 

Road Mining District west of Hanna are 

subbituminous A and are suspected to be highvolatile C bituminous underlying the Hanna 

Formation at Hanna (Dyman and Condon, 2007).

The Medicine Bow-Ferris-Hanna Coalbed Gas AU was 

not quantitatively assessed because of a lack of geologic 

and production data. Current production for producing 

cells is less than the minimum recovery per cell required 

for assessment (Dyman and Condon, 2007).

Individual coals in the Hanna Formation are thicker, on 

average, than those of the Ferris Formation; cumulative coal 

thicknesses range from 30 - 375 ft and 125 - 305 ft, 

respectively (Glass and Roberts, 1980). Between the Hanna 

Basin and the Carbon Basin (a synclinal area between the 

Hanna and Laramie Basins), coals in the Hanna Formation are 

locally offset by faulting and are therefore difficult to correlate. 

Medicine Bow coals are not as laterally persistent as those of 

the Hanna and Ferris Formations (Merewether, 1971, 1972, 

1973; Glass and Roberts, 1980; as reported in Dyman and 

Condon, 2007).

Mesaverde Coalbed Gas AU—Not 

quantitatively assessed (Dyman and others, 

2006) Cretaceous (Dyman and Condon, 2007)

Steep dips and faults are encountered in wells, and Mesaverde coals 

are deep. In the Anadarko Petroleum Durante 11–2 well, the 

Mesaverde was not reached at 19,600 ft. Thermal gas would be 

expected from gas-prone coaly source rocks at such extreme depths 

(Dyman and Condon, 2007).

In the central Hanna Basin, Medicine Bow and 

Almond coals are expected to be high-volatile A 

or B bituminous coals (Dyman and Condon, 

2007).

The Mesaverde Coalbed Gas AU was not quantitatively 

assessed because of a lack of geologic and production 

data. Current production for producing cells is less than 

the minimum recovery per cell required for assessment 

(Dyman and Condon, 2007).

Seven laterally persistent coal beds greater than 5 ft thick have 

been described for the deeper Almond coals, and cumulative 

coal thickness ranges from 10 - 40 ft. Mesaverde coals are 

deep, and steep dips and faults are encountered in wells in the 

northern part of the Hanna Basin (Dyman and Condon, 2007).

Although these data have been processed successfully on a 

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This report is available at:

http://pubs.usgs.gov/ds/683/ 

 

Publishing support provided by: 

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Manuscript approved for publication on 03/30/2012

For more information concerning this publication, contact:

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Or visit the Central Energy Resources Team site at:

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Wells must undergo dewatering before gas flows. 

Greater Green River

Supporting geologic studies of Total Petroleum Systems and Assessment Units and a report on the methodology used in the Wyoming Thrust Belt Province assessment are in progress. Assessment results are available at the USGS Central Energy Team website: 

http://energy.cr.usgs.gov/oilgas/noga/

Coal-rich source rocks, such as the Almond 

Formation of the Mesaverde Group, and the 

Medicine Bow, Ferris, and Hanna 

Formations, of sufficient thickness for 

generating biogenic and minor amounts of 

thermal gas, were deposited in coastal and 

nonmarine environments (Dyman and 

Condon, 2007).

Hanna and Carbon Basins 

(Dyman and Condon, 2007)

Coalbed Gas Assessment Units in Southwestern Wyoming

Compiled by

Laura R.H. Biewick

2012

Drilling is still in its early stages, and gas production is limited. Data are insufficient to identify areas where coalbed gasgenerating potential exists (Dyman and Condon, 2007).

U.S. DEPARTMENT OF THE INTERIOR

Wyoming Landscape Conservation Initiative (WLCI) – a multi-partner, long-term, science-based program to assess, monitor, and enhance aquatic and terrestrial habitats at a landscape scale in southwest Wyoming, while facilitating responsible 

development through local collaboration and partnerships (http://www.wlci.gov/).

Definitions

Total Petroleum System (TPS) – the essential elements (source rock, reservoir rock, seal rock, and overburden rock) and processes (generation, migration, accumulation, and trap formation) as well as all genetically related petroleum that 

occurs in seeps, shows, and accumulations, both discovered and undiscovered, whose provenance is a pod or closely related pods of active source rock. The TPS is a naturally occurring hydrocarbon-fluid system in the lithosphere that can be 

mapped, and includes the essential elements and processes needed for oil and gas accumulations to exist (Magoon and Schmoker, 2000).

Assessment Unit (AU) – a volume of rock within the TPS that encompasses fields, discovered and undiscovered, sufficiently homogeneous in terms of geology, exploration strategy and risk characteristics to constitute a single population of 

field characteristics with respect to criteria used for resource assessment. AUs are considered established if they contain more than 13 discovered fields, frontier if they contain 1−13 discovered fields and hypothetical if they contain no 

discovered fields (Magoon and Schmoker, 2000).