U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2015–3052

August 2015

National and Global Petroleum Assessment

Introduction

The U.S. Geological Survey (USGS) recently completed 

a geology-based assessment of conventional and continuous 

(unconventional) oil and gas resources of the informal Uteland 

Butte member (Osmond, 1992) of the Eocene Green River 

Formation, Uinta Basin, Utah (fig. 1). The recent successful 

development of a tight oil play in the informal Uteland Butte 

member, using modern horizontal drilling and hydraulic fracturing techniques (Durham, 2013; Anderson and Roesink, 2013; 

Vanden Berg and others, 2014), has spurred a renewed interest 

in the tight oil potential of lacustrine rocks.

Assessment Units

The USGS defined a Green River Total Petroleum System 

(TPS) and two assessment units (AU) within the TPS: (1) the 

Uteland Butte Carbonate Continuous Oil Assessment Unit; and 

(2) the Uteland Butte Conventional Oil and Gas Assessment Unit 

(fig. 1). Key input data used to assess the informal Uteland Butte 

member are in table 1.

The Uteland Butte Carbonate Continuous Oil AU covers much of the deep central part of the Uinta Basin (fig. 1) and 

consists largely of organic-rich offshore lacustrine carbonate and 

shale. The most productive reservoir rock and the main target for 

horizontal drilling is highly porous, largely impermeable dolomite 

beds, but significant oil is also present in adjacent organic-rich 

shale and micritic limestone beds. The Uteland Butte Carbonate 

Continuous Sweet Spot or area with unusually high estimated 

ultimate recoveries (EURs), is present in the north-central part 

of the AU in an area of abnormally high formation pressures. 

Overpressure appears to be the most important factor in predicting 

Uteland Butte production, but other factors also play a role including: (1) total thickness of the Uteland Butte member; (2) total 

thickness of dolomite beds; (3) organic richness; and (4) thermal 

maturity. The overpressured sweet spot was defined using drilling 

mud weights (Anderson and Roesink, 2013) and drill stem tests.

The Uteland Butte Conventional Oil and Gas AU is divided 

into two areas, one along the north margin of the basin and the 

other in the south-central part of the basin (fig. 1). The two areas 

are in quite different geologic settings. The north area is in marginal lacustrine rocks along the deep basin trough where thermal 

maturities are high and overpressure is locally encountered. Oil is 

trapped by the updip pinch out of marginal lacustrine clastic and 

carbonate reservoirs into offshore lacustrine carbonate and shale 

of the Uteland Butte Carbonate Continuous Oil AU to the south. 

Using a geology-based assessment methodology, the U.S. 

Geological Survey estimated mean undiscovered resources of 

214 million barrels of oil, 329 billion cubic feet of associated/

dissolved natural gas, and 14 million barrels of natural gas 

liquids in the informal Uteland Butte member of the Green 

River Formation, Uinta Basin, Utah.

Figure 1. U.S. Geological Survey Uinta-Piceance Basin Province of Utah

and Colorado, the Uteland Butte Conventional Oil and Gas Assessment 

Unit (AU), the Uteland Butte Carbonate Continuous Oil Assessment Unit 

and the geologic sweet spot within the assessment unit.

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Price

Heber

Vernal

Gunnison

Grand

Junction

Glenwood

Springs

Uinta Basin

Source: US National Park Service

41°

40°

39°

38°

COLORADO

UTAH

WYOMING

Source: National Park Service (2015)

–111° –110° –109° –108° –107° –106°

CO

WY

UT

AZ NM

ID SD

NE Area

of

Study

Uinta-Piceane Basin Province

Uteland Butte

Carbonate

Continuous AU

Uteland Butte Carbonate

Continuous Sweet Spot

Uteland Butte

Conventional

Oil and Gas AU

0 50 KILOMETERS

0 50 MILES

The south area of the Uteland Butte Conventional Oil and Gas AU, 

in contrast, is in marginal lacustrine rocks along the south margin of 

the basin where thermal maturity is low and formation pressures are 

near normal. Trapping mechanism in the south segment is probably 

the updip pinch out of individual marginal lacustrine clastic units into 

alluvial mudstone. 

The Uteland Butte Conventional Oil and Gas AU consists 

largely of sandstone, siltstone, carbonate, and mudstone deposited 

in a marginal lacustrine setting. Oil migrated into this AU from 

thermally mature, organic-rich offshore lacustrine rocks of the 

informal Uteland Butte member. The Uteland Butte Conventional 

Oil and Gas AU is thought to contain mainly undiscovered oil fields 

but some gas fields are also likely to be present. There is abundant 

evidence for vertical migration of gas in the basin from deeper, 

gas-prone source rocks in the underlying Upper Cretaceous interval (Rice and others, 1992). Some of this gas has migrated into the 

marginal lacustrine facies of the informal Uteland Butte member 

and may be trapped where an adequate seal is present.

Resource Summary

The USGS assessed undiscovered, technically recoverable 

continuous (unconventional) and conventional resources in the 

informal Uteland Butte member. Mean resources for the Uteland 

Butte Carbonate Continuous Oil AU are 177 million barrels of oil 

(MMBO); 218 billion cubic feet of gas (BCFG); and 10 million 

barrels of natural gas liquids (MMBNGL) (table 2). Mean resources 

for the Uteland Butte Conventional Oil and Gas AU are 37 MMBO; 

111 BCFG; and 4 MMBNGL (table 2).

Assessment of Undiscovered Oil and Gas Resources in the Uteland Butte 

Member of the Eocene Green River Formation, Uinta Basin, Utah
References Cited

Anderson, J.G., Roesink, J.G., 2013, Reservoir characterization 

of the Uteland Butte Formation in the Uinta Basin: American 

Association of Petroleum Geologists, Search and Discovery 

Article #50888, 2 oversized sheets.

Durham, L.S., 2013, Unconventional Uteland Butte sparks new 

Utah activity: American Association of Petroleum Geologists 

Explorer, June 2013.

Osmond, J.C., 1992, Greater Natural Buttes gas field, Uintah 

County, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, 

T.C., Jr., eds., Hydrocarbon and mineral resources of the 

Uinta Basin, Utah and Colorado: Utah Geological Association 

Guidebook No. 20, p. 143–163.

Rice, D.D., Fouch, T.D., and Johnson, R.C., 1992, Influence of 

source rock type, thermal maturity, and migration on composition and distribution of natural gases, Uinta Basin, Utah, in 

Fouch, T.D., Nuccio, V.F., and Chidsey, T.C. Jr., eds., 

Table 1. Key assessment input data for one continuous and one conventional assessment unit 

in the informal Uteland Butte member, Uinta-Piceance Basin Province.

[EUR, estimated ultimate recovery per well; MMBO, million barrels of oil; BCFG, billion cubic feet of gas; AU, 

assessment unit; %, percent. The average EUR input is the minimum, median, maximum, and calculated mean]

Assessment input data–continuous AU

Uteland Butte Carbonate

Continuous Oil AU Minimum Mode Maximum Calculatedmean

Potential production area of AU (acres) 400,000 700,000 1,373,000 824,333

Average drainage area of wells (acres) 120 160 200 160

Percentage of total AU area that is untested (%) 98 99 99.5 98.8

Success ratio (%) in sweet spots 80 95 100 91.7

Average EUR (MMBO) in sweet spots 0.06 0.085 0.14 0.088

Success ratio (%) in nonsweet spots 30 50 70 50.0

Average EUR (MMBO) in nonsweet spots 0.03 0.044 0.09 0.046

AU probability 1.0

Assessment input data–conventional AU

Uteland Butte Conventional

Oil and Gas AU Minimum Median Maximum Calculatedmean

Number of oil fields 1 12 40 12.93

Number of gas fields 1 4 10 4.19

Sizes of oil fields (MMBO) 0.5 2 30 2.86

Sizes of gas fields (BCFG) 3 12 180 17.08

AU probability 1.0

 Hydrocarbon and mineral resources of the Uinta Basin, Utah 

and Colorado: Utah Geological Association Guidebook 

No. 20, p. 95–110.

Vanden Berg, M.D., Wood, R.E., Carney, S.M., Morgan, C.D., 

2014, Geological characterization of the Uteland Butte 

Member of the Eocene Green River Formation—An emerging unconventional carbonate tight oil play in the Uinta Basin, 

Utah: in Program and Abstracts, Rocky Mountain Association 

of Geologist—American Association of Petroleum Geologists 

Annual Meeting, July 20–22, 2014, p. 44.

ISSN 2327-6916 (print) ISSN 2327-6932 (online) http://dx.doi.org/10.3133/fs20153052

Uteland Butte Assessment Team

Ronald C. Johnson, Justin E. Birdwell, Tracey J. Mercier, 

Michael E. Brownfield, Ronald R. Charpentier, Timothy R. 

Klett, Heidi M. Leathers, Christopher J. Schenk, and Marilyn 

E. Tennyson.

Total Petroleum System (TPS) 

and

Assessment Units (AUs)

AU 

probability

Accumulation type

Total undiscovered resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Green River TPS

Uteland Butte Carbonate 

Continuous Oil AU 1.0 Oil 104 170 272 177 98 205 383 218 4 9 20 10

Total unconventional

 resources 104 170 272 177 98 205 383 218 4 9 20 10

Green River TPS

Uteland Butte Conventional

Oil and Gas AU 1.0 Oil 15 34 70 37 15 35 74 39 1 1 3 2

 Gas 27 63 148 72 1 1 3 2

Total conventional

 resources 15 34 70 37 42 98 222 111 2 2 6 4

Total undiscovered

 resources 119 204 342 214 140 303 605 329 6 11 26 14

Table 2. Assessment results for continuous and conventional oil and gas resources in the informal Utland Butte member, Uinta-Piceance 

Basin Province.

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids; TPS, total petroleum system; AU, assessment unit. 

Results shown are fully risked estimates. For gas accumulations, all liquids are included under the NGL (natural gas liquids) category. F95 represents a 95 percent 

chance of at least that amount tablulated. Other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. Shading indicates not applicable]