U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3010

May 2010

Assessment of In-Place Oil Shale Resources of the Green 

River Formation, Uinta Basin, Utah and Colorado

Printed on recycled paper

Introduction

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

a reassessment of in-place oil shale resources, regardless of 

richness, in the Eocene Green River Formation in the Uinta 

Basin, Utah and Colorado (fig. 1). The oil shale interval in the 

Uinta Basin is subdivided into eighteen “rich” and “lean” zones 

(fig. 2) that were assessed separately. These zones, originally 

defined by Cashion and Donnell (1972), are roughly timestratigraphic units consisting of distinctive, laterally continuous intervals of rich and lean oil shale beds that can be traced 

throughout much of the Uinta Basin. This assessment uses 

oil-yield values in gallons per ton (GPT) from four sources: (1) 

Fischer-assayed samples from core holes specifically cored to 

assess oil shale, (2) Fischer-assayed cuttings from oil and gas 

tests, (3) Fischer-assayed surface samples, and (4) estimated oil 

yields from surface samples. Core data are confined largely to 

the eastern and southeastern parts of the basin (fig. 1) where rich 

oil shale intervals occur at shallow depth favorable for development. Results from cuttings are less precise than those from 

core, and there is the ever-present possibility of contamination 

from uphole caving. To minimize these effects, this study used 

only cuttings data in which the sample collection interval is no 

greater than 10 ft, missing intervals are minimal, and the characteristic pattern of rich and lean zones, established from core 

results (fig. 2), are clearly delineated on oil-yield histograms. 

Comparisons of results from cuttings data and nearby core holes 

indicate that cuttings data are 10–20 percent too low for rich oil 

shale zones and as much as 10 percent too high for most lean oil 

shale zones. We did not apply any correction factors to the cuttings data for this assessment. Surface samples were used only 

in areas where no core or cuttings data were available. 

The Fischer assay method is a standardized laboratory 

test for determining the oil yield from oil shale that has been 

almost universally used to determine oil yields for Green River 

Formation oil shales (Stanfield and Frost, 1949; American 

Society for Testing and Materials, 1980). Fischer assay does 

not necessarily measure the maximum amount of oil that an oil 

shale can produce, and there are retorting methods that yield 

Oil Shale Assessment Project Fact Sheet

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

Geological Survey estimated a total of 1.32 trillion barrels of 

oil in place in eighteen oil shale zones in the Eocene Green 

River Formation in the Uinta Basin, Utah and Colorado. 

Photo: Evacuation Creek, Uinta Basin, northeastern Utah.
R 103 W

R 3 W R 2 W R 12 W R 11 W R 10 W R 9 W R 8 W R 7 W R 6 W R 5 W R 4 W R 1 W R 1 E R 24 E R 25 E R 6 E

R 20 E R 21 E

R 25 E

T

16

S

R 22 E R 23 E

R 19 E

R 23 E R 24 E

R 23 E

R 22 E

T

17

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R 19 E R 20 E R 21 E

T

18

S

T

19

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14

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15

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R 17 E

R 18 E

R 16 E

T

16

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18

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15

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14

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R 15 E

R 14 E

R 2 E

T

13

S

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12

S

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11

S

R 13 E R 10 E R 11 E R 12 E

T

6

S

R 8 E

R 6 E R 7 E

T

10

S

T

9

S

T

8

S

T

7

S

T

3

S

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4

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5

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13

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7

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2

N

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1

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MOFFAT

SEVIER

UINTAH

UTAH

GARFIELD

MESA

SANPETE

RIO BLANCO

CARBON

DUCHESNE

EMERY

GRAND

WASATCH

£¤191

£¤6

£¤40

§ ̈¦70

Price

Roosevelt

Vernal

111°00' 110°30' 110°00' 109°30' 109°00'

40°00'

39°30'

39°00' 0 6 12MILES

0 5 10KILOMETERS UTAH UTAH COLORADO

Area underlain by oil shale rocks

(Cut-off to north is at 6,000-ft depth

to Mahogany bed).

City or town

County line

Core hole 

Rotary hole

Surface sample

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Figure 1. Distribution of oil shale deposits in the Eocene Green River Formation, Uinta Basin, Utah and Colorado. Control points 

used in resource assessment are shown.

1

Any use of trade, product, or firm names is for descriptive purposes only and 

does not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured 

from the individual copyright owners to reproduce any copyrighted material 

contained within this report.

more oil volume than the Fischer assay method. Oil yields 

achieved by other technologies, however, are typically reported 

as a percentage of the Fischer assay oil yield, and thus Fischer 

assay is still considered the standard to which other methods are 

compared.

Methodology

In this assessment, a spatial interpolation and extrapolation 

method for generating resource maps and computing resource 

volumes was used—the Radial Basis Function (RBF) in ArcGIS 

GeoStatistical Analyst (Environmental Systems Research Institute, Inc.1

 (ESRI), Redlands, Calif., 2006, version 9.2).

The RBF method in GeoStatistical Analyst is an exact 

interpolator; it will honor all data points without introducing 

errors at those locations. Where it is important for the modeling 

method to honor the measured values, RBF can also extrapolate 

values above or below the actual values away from the datapoint locations. The final resource models for each oil shale 

zone were created using a sampling method containing eight 

moving window sectors with eight neighbors in each sector.

Although the RBF method does not generate as complete 

an error estimate as kriging, it does give the difference between 

the predicted and measured value for each control point, and it 

does give an overall difference value for an entire oil shale zone 

model. To obtain the difference between the predicted value and 

the measured value, the RBF method predicts a value at a given 

control point from the nearest control points (in this assessment, 

eight neighbors are used) without knowing the actual value 

measured at that control point. That predicted value is then 

compared with the measured value, and the difference between 

the two is calculated.
Top bed 44-

top A-groove

A-groove

Mahogany

zone

B-groove

R-6 zone

L-5 zone

R-5 zone

L-4 zone

R-4 zone

L-3 zone

R-3 zone

L-2 zone

R-2 zone

L-1 zone

R-1 zone

L-0 zone

R-0 zone

Stratigraphic nomenclature for 

oil shale zones from Donnell 

and Blair, 1970, Cashion and 

Donnell, 1972, Donnell, 2009. Garden Gulch Member Parachute Creek Member Green River Formation (part)

Oil yield (gallons per ton)

 U-53

Skyline Oil Co., Watson 1A

 Sec. 5, T. 11 S., R. 25 E.

Top bed 76-top

bed 44

0

0

20 40 60 80 100

0 20 40 60 80 100

500 ft 

1,000 ft

1,500 ft

2,000 ft

Rich oil shale zones—

carbonate rich

Lean oil shale zones—

carbonate rich

Rich oil shale zones—

clay rich

Lean oil shale zones—

clay rich

EXPLANATION

Figure 2. Oil-yield histogram in gallons per ton (shown in 

red) and the rich and lean oil shale zones in the Green River 

Formation assessed in this study.

Table 1. Oil shale resources by rich (R) and lean (L) zones in 

barrels for the Uinta Basin, Utah. [1 barrel of oil = 42 gallons]

Uinta Basin Oil Shale Resource Assessment

Bed 76 to Bed 44 168,960,275,000

Bed 44 to A-groove 244,681,783,000

A-Groove 15,254,421,000

Mahogany Zone 214,578,720,000

B-Groove 37,204,118,000

R6 176,618,343,000

L5 43,951,157,000

R5 83,410,082,000

L4 24,437,647,000

R4 70,540,940,000

L3 1,375,801,000

R3 3,763,406,000

L2 1,738,790,000

R2 10,878,365,000

L1 4,985,817,000

R1 95,374,910,000

L0 5,824,455,000

R0 115,384,563,000

Total 1,318,963,593,000

Resource Summary

Table 1 lists the estimated total in-place oil for each oil 

shale zone in the Uinta Basin in barrels. Richest oil shale zones 

in the basin are, in ascending stratigraphic order, (1) R-0 zone, 

115.4 billion barrels; (2) R-6 zone, 176.6 billion barrels; (3) 

Mahogany zone, 214.6 billion barrels, (4) Bed 44 to A-groove, 

244.7 billion barrels, and (5) Bed 76 to Bed 44 with 169.0 billion barrels. Total in-place oil in the eighteen oil shale zones 

assessed is 1.32 trillion barrels (table 1). Figure 3 shows total 

in-place oil in each township for all 18 oil shale zones combined. The richest resources are in a northwest-trending area of 

the northeastern part of the basin (fig. 3). Maximum in-place oil 

in a township is over 30 billion barrels in T. 9 S., R. 23 E.
R 103 W

R 3 W R 2 W R 12 W R 11 W R 10 W R 9 W R 8 W R 7 W R 6 W R 5 W R 4 W R 1 W R 1 E R 24 E R 25 E R 6 E

R 20 E R 21 E

R 25 E

T

16

S

R 22 E R 23 E

R 19 E

R 23 E R 24 E

R 23 E

R 22 E

T

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R 19 E R 20 E R 21 E

T

18

S

T

19

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T

14

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R 17 E

R 18 E

R 16 E

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R 15 E

R 14 E

R 2 E

T

13

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T

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S

T

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R 13 E R 10 E R 11 E R 12 E

T

6

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R 8 E

R 6 E R 7 E

T

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T

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T

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18,969 25,294 27,707 28,566 30,398 27,473 15,149 17,180 16,509 5,798 13,435

27,255 27,979 23,987 19,469 19,985 16,886

5,548 6,579 8,029 1,054

541 666 991 1,522 1,554

8,159 14,911 12,136 20,188 23,408 24,663

1,912

802 4,100 5,713 5,983 8,645 8,919 3,340

1,952 6,536

4,867 5,618 6,334 6,178 8,794 9,846 6,763 7,000 1,368

4,696 5,662 8,483 7,686 8,106 8,591 11,076

4,669

12,453 21,952 13,550 17,894

1,750 3,319 4,994 7,324 8,152 7,378 9,301 15,406 14,274 17,176 17,150

361

5,671

2,918

3,325

5,367

4,737

77 46 85

121 221 256 246

26

131

422 400 255 576 507

85 12 322 602

907 744 457

104

354

765

105 209 555 679

2,051 1,148 816 246 995 2,059

398

2,609 750

3,795 2,608 3,578 2,497 5,528 1,929

404

2,171

2,378 1,316

2,104 2,060 8,931 9,895 9,931 11,176 11,278 10,861 2,594

1,895 721 1,256

15,254 11,982 13,058 13,509 15,499 20,509 19,617 8,890 8,023 8,335 2,528 4,465 2,364 1,652 2,355

14,373 11,627 12,343 14,631 17,006 19,467 19,748 25,314 29,162 26,410 8,746 874

111°00' 110°30' 110°00' 109°30' 109°00'

40°00'

39°30'

39°00'

0 6 12 MILES

0 5 10 KILOMETERS UTAH

EXPLANATION

Utah Outcrops

Top of Mahogany bed outcrop

Depth to Mahogany bed, 6,000 ft contour

Base of Parachute Creek Member

Defined boundary for assessment

Total in-place resources per township in millions of barrels

> 30,000

22,501 – 30,000

15,001 – 22,500

7,501 – 15,000

< 7,500

UTAH

COLORADO

Figure 3. Total in-place oil in millions of barrels as assessed for each township in the Uinta Basin, Utah and Colorado.

Stanfield, K.E., and Frost, I.C., 1949, Method of assaying oil shale 

by a modified Fischer retort: U.S. Bureau of Mines Report of 

Investigations 4477.

For Additional Information

Supporting geologic studies of the oil shale-bearing units, 

assessment units, oil shale analysis, and the methodology used 

in assessing the oil shale resources in the Uinta Basin are in 

progress. Assessment results are posted as they become available at the USGS Central Energy Team Web site: http:/energy.

cr.usgs.gov/oilshale.

Contact Information

For further information contact Ronald C. Johnson 

(rcjohnson@usgs.gov), Tracey J. Mercier (tmercier@usgs.gov), 

Michael E. Brownfield (mbrownfield@usgs.gov), or Jesse G. 

Self (jself@usgs.gov).

References

American Society for Testing and Materials (ASTM), 1980, 

Standard method of test for oil from oil shale: Annual Book 

of ASTM Standards, Part 25, Designation D 3904–80, 

p. 513–515.

Cashion, W.B., and Donnell, J.R., 1972, Chart showing correlation of selected key units in the organic-rich sequence of the 

Green River Formation, Piceance Creek Basin, Colorado, 

and Uinta Basin, Utah: U.S. Geological Survey Oil and Gas 

Investigations Chart OC–65.

Donnell, J.R., 2009, Intertonguing of the lower part of the Uinta 

Formation with the Upper part of the Green River Formation 

in the Piceance Creek Basin during the late stages of Lake 

Uinta: U.S. Geological Survey Scientific Investigations Report 

2008–5237, 24 p. 

Donnell, J.R., and Blair, R.W., 1970, Resource appraisal of three 

rich oil-shale zones in the Green River Formation, Piceance 

Creek basin, Colorado: Colorado School of Mines Quarterly, v. 

65, p. 73–87.