Preliminary Report on 

I Oil-Shale Resources of 

Piceance Creek Basin 

s Northwestern Colorado

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GEOLOGICAL SURVEY BULLETIN 1042-H

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CONTRIBUTIONS TO ECONOMIC GEOLOGY

PRELIMINARY REPORT ON OIL-SHALE RESOURCES OF 

PICEANCE CREEK BASIN, NORTHWESTERN COLORADO

By JOHN R. DONNELL

ABSTRACT

Oil shale in the Green River formation of Eocene age underlies an area of about 

1,400 square miles in that part of the Piceance Creek basin in Rio Blanco and 

Garfield Counties, Colo., that lies between the Colorado River to the south and 

the White River to the north.

Preliminary estimates of tonnage and oil content of the oil shale include indicated and inferred potential reserves which may be combined as follows: (1) part 

of the richest oil-shale zone (the Mahogany zone) yielding an average of 45 gallons 

of oil per ton and ranging from 5 to 31 feet in thickness contains a total of more 

than 7 billion tons of shale and 7.5 billion barrels of oil, (2) shale zones yielding 

an average of 30 gallons of oil per ton and ranging from 15 to 180 feet in thickness 

contain about 137.5 billion tons of shale and about 98.8 billion barrels of oil, 

(3) shale zones yielding an average of 25 gallons of oil per ton and ranging from 15 

to 780 feet in thickness contain about 325 billion tons of shale and about 194 

billion barrels of oil, (4) shale zones yielding an average of 15 gallons of oil per 

ton and ranging from 15 to 2,200 feet in thickness contain about 2,686 billion' 

tons of oil shale, with an oil content of 959 billion barrels. The estimates reflect 

the total size and oil content of the deposits, and no allowance is made for losses 

that would be incurred in mining and processing of the oil shale.

INTRODUCTION

The part of the Piceance Creek basin described in this report covers 

an area of about 1,400 square miles in northwestern Colorado, almost 

entirely in Rio Blanco and Garfield Counties. The area is bounded 

by the Colorado River on the south (fig. 30), the White River on the 

north, Douglas Creek and the East Fork of Salt Wash on the west, 

and Government and Sheep Creeks on the east. The oil shales are 

found in the lacustrine Green River formation of middle Eocene age, 

which attains a maximum thickness of about 3,500 feet. Underlying 

the Green River formation are variegated shales and lenticular sandstones of the Wasatch formation of Paleocene and early Eocene age. 

The Wasatch formation is about 5,500 feet thick in General Petroleum 

Corp. gas well 84-15-G, sec. 15, T. 2 S., R. 96 W., on the Piceance

255

402959 57
256 CONTRIBUTIONS TO ECONOMIC GEOLOGt
OIL-SHALE RESOURCES, PICEANCE CREEK BASIN, COLORADO 257

Creek dome in the east-central part of the basin. Underlying the 

Wasatch formation is the Mesaverde formation of Late Cretaceous 

age.

That part of the area which is underlain by the Green River formation is a high plateau rising about 4,400 feet above the valley of the 

Colorado River near Rifle and attaining an altitude of 9,400 feet. 

The whitish and light-blue cliffs of the resistant oil shale are in sharp 

contrast to the low-relief badlands topography of the Wasatch formation bordering the plateau.

The Piceance Creek basin is a structural basin which coincides 

approximately with the original basin of deposition of the Late 

Cretaceous and early Tertiary sediments. Steep westerly dips on the 

eastern margin reflect the sharp monoclinal flexure of the Grand 

Hogback, whereas the gently east-dipping Green River strata on the 

western margin form the eastern flank of the Douglas Creek anticline. 

Thinning of formations toward the margins indicates that it was formerly a basin of deposition. The Wasatch formation, which attains 

its maximum known thickness of 5,500 feet on the Piceance Creek 

dome in T. 2 S., R. 96 W., thins to 375 feet about 25 miles to the 

northwest. Westward thinning also occurs in the underlying Mesaverde and Mancos formations.

The Green River formation, as described by Bradley (1931), consists of four members which are, in ascending order, Douglas Creek, 

Garden Gulch, Parachute Creek, and Evacuation Creek. The richer 

shales which may ultimately be of economic interest are mostly 

confined to the Parachute Creek member, which in turn is divided 

into the upper and lower oil-shale zones. These rich oil-shale zones 

are extremely resistant to weathering and form sheer cliffs or steep 

slopes. They are separated by a thin sequence of lean oil shale that 

weathers to a gentle slope or recess. In the lower part of the upper 

oil-shale zone is the Mahogany ledge, a unit that contains the principal 

oil-shale beds in the sequence. Everywhere that the ledge crops out 

it forms a sheer cliff delimited above and below by lean shales that 

form slopes. The subsurface counterpart of the Mahogany ledge is 

referred to in this report as the Mahogany zone. The ledge, or zone, 

is about 110 feet thick at the axis of the basin and thins toward the 

margins. Undoubtedly the first segment of the oil-shale sequence to 

be worked commercially will include part or all of the Mahogany zone. 

The U. S. Bureau of Mines experimented in mining a 78-foot section 

of shale in the Mahogany zone at their mine just west of Rifle.

The richest oil-shale bed within the Mahogany ledge, or zone, is

called the Mahogany bed, which is used as a stratigraphic reference bed.

Interest in development of oil shale in northwestern Colorado began

about 1916, and activity has continued, with varying degrees of inten-
258 CONTRIBUTIONS TO ECONOMIC GEOLOGY

sity, until the present. Private companies, the U. S. Bureau of Mines, 

and the U. S. Geological Survey have assayed core from 43 core holes 

and 32 surface sections, and the Bureau of Mines has assayed rotary 

cuttings from 13 wells of the General Petroleum Corp. This information, together with 16 incompletely sampled surface sections made by 

Dean E. Winchester, of the Geological Survey, between 1916 and 1921 

(Winchester, 1917, 1923), and the estimated oil content of 36 surface 

sections measured by field parties of the Survey since 1945, were used 

in the calculation of the oil-shale resources.

Descriptions of the geology and oil-shale resources of several areas 

within the Piceance Creek basin have been published recently (Duncan 

and Denson, 1950; Duncan and B°lser, 1950; Waldron, Donnell, and 

Wright, 1951; Donnell, Cashion, and Brown, 1953).

W. B. Cashion, Jr., William M. Zilhersher, J. H. Brown, Jr., M. G. 

Wolman, W. C. Gibson, and K. K. Enghm«J have assisted the writer 

at different times since June 1949.

The following companies, Government agencies, and individuals 

furnished much of the information upon which the tonnage and oil 

content of the shale were calculated: U. S. Bureau of Mines, Union 

Oil Co. of California, Standard Oil Co. of California, Sun Oil Co., 

Cities Service Oil Co., Phillips Petroleum Co., Pure Oil Co., Continental Oil Co., Gulf Oil Corp., General Petroleum Corp., Weber Oil 

Co., Denver Research Institute, Charles Prien, John Savage, W. O. 

Pray, J. T. Julian, and Tell Ertl.

CRITERIA TJ^-ED IN MAKINQ ESTIMATES OF TONNAOE

AND OIL CONTENT OF OIL SHALE

To compute the tonnage and oil content of the oil ?hale, the oil-shale

sequence was divided into several units on the basis of average Oil 

yield, and reserves were computed separately for shale yielding respectively 15, 25, 30, and 45 gallons per ton. A minimum thickness 

of 5 feet was used for shale averaging 45 gallons per ton; a minimum

thickness of 15 feet was used for the other grades.

The minimum thicknesses and grades of oil shale used in this report 

in part correspond approximately to the minimum thicknesses anrf 

grades of oil shale exploited on a SUStflillfid basis 111 Other parts Of the 

World. In Estonia, for example, oil shales (Kukersite) in beds ranging:

from about 5 to 8 feet in thickness and yielding from 45 to 55 gaiio 

of oil per ton have been mined and processed for oil since about 1921

CLutz, 1938; Guthrie and Klosky, 1951). Oil shales yielding as little

fifS'lt? gallons of oil per ton have been mined on large scale and processed in other places, such as in Sweden (Cadman, 1948 j Guthrie and 

Klosky, 1951).
OIL-SHALE RESOURCES, PICEANCE CREEK BASEST, COLORADO 259

There has thus far been no large-scale commercial development of 

oil shale in this country; therefore it is not possible to predict with 

assurance what average grade will eventually prove most suitable, or 

what the minimum minable thickness, will be. Results of research in 

processing oil shale by the U. S. Bureau of Mines at a pilot plant near 

Rifle indicate an optimum grade ranging between 25 and 33 gallons of 

oil per ton, and the underground mining methods developed by the 

Bureau require a minimum thickness of 25 feet of shale equal to the 

minimum operating room required by the equipment used. Continued 

advancements in the technology of mining and processing oil shale 

may alter these limits, consequently a wider range in grade and thickness was used in this report. Moreover, no attempt is made to predict 

what proportion of the oil will be lost in mining and processing of the 

oil shale, and no allowance is made for such losses in the estimates of 

tonnage and oil content of the shale.

METHODS USED IN COMPUTING ESTIMATES OF 

TONNAGE AND OIL CONTENT OF OIL SHALE

For each locality where there was information on the oil content of 

the shale sequence, the data were studied to determine the maximum 

thicknesses of shale in continuous sequence that have an average assay 

value of 15, 25, 30, and 45 gallons per ton, respectively. Thickness 

data so obtained were then used to construct a series of thickness maps 

(pi. 14, A-D) from which the average thickness of each grade of oil 

shale was estimated for each township. The volume of oil shale of 

given grade in each township was then computed and converted to 

tonnage by using the estimated specific gravity of the shale.

The basic information on oil content generally consists of individual 

assays of a series of samples taken in vertical sequence; the samples 

may vary considerably both in thickness of strata represented and in 

oil content. Specific gravity determinations are not made in routine 

assays, but it has been established that lean oil shale is denser than 

rich oil shale (Belser, 1951, p. 5). In combining the assay data on 

a series of individual samples to determine the average assay value 

of the total thickness, the values of the individual samples were 

weighted according to the thickness of strata represented but were not 

weighted according to specific gravity. Where assays of samples of 

varying richness are combined, failure to weight the sample data 

according to specific gravity results in a slightly higher-than-actual 

average assay value. However, this source of error is generally 

small, particularly where the range in assay value is not large, 

which is generally true in practice. As other uncontrolled or 

unappraisable factors involved in the reserve estimates represent 

greater theoretical sources of error, and as actual specific gravity
260 CONTRIBUTIONS TO ECONOMIC GEOLOGY

determinations on the individual samples were not made, weighting 

of the sample data according to estimated density was considered 

unwarranted for this inventory. Although various assay methods 

were used to determine the oil.content of the shale, most of the samples were analyzed by the modified Fischer assay method, as described 

by Stanfield, Frost, McAuley, and Smith (1951), who indicate that 

the yields and characteristics of the products by this method may not 

be comparable to those obtained under different retorting conditions 

or derived from commercial size units. The relative oil yields and 

data on products obtained from some larger experimental retorts are 

described by Guthrie (1955).

Estimates of tonnage and oil content of the oil shale have been 

broken down into two categories, indicated and inferred, that are 

intended to show the relative reliability of the estimates. Tonnage 

and oil content in the indicated category are considered more accurate 

than the inferred category. In most places, areas that have analyses 

of cores spaced less than 6 miles apart contain indicated potential 

reserves. A few areas where these cores are spaced more than 6 miles 

apart but where the general increase or decrease in organic content 

is indicated to be uniform by many nearby cores are also regarded 

as areas of indicated potential reserves. Reserves within approximately 2 miles of an isolated analyzed set of samples are regarded as 

indicated. If there are several sets of analyzed data roughly in line,

then lines 2 miles from this alinement form the outer limits of indicated reserves. Reserves within 2 miles of a well with analyzed rotary 

cuttings, or within 2 miles of a group of wells whose rotary cuttings

have been analyzed, are considered indicated for shale averaging 15 

gallons of oil per ton. Rotary-cutting sample intervals are generally

10, 20, Or 25 feet and are considered too great for even the moderate

reliability desired to classify- indicated reserves of 25- and 3O-gallon

shale and are considered inadequate for estimating potential reserves

of the thin shale unit containing 45 gallons per ton.

Surface sections are exposed to weathering and in the weathering 

process may lose as much as 50 percent of their oil content (Winchester, 1917, p. 162-163, pi. 14). Also, lean oil shale breaks much

more easily than rich oil shale, and, unless great care is taken to cut 

a uniform channel through the sequence, a representative sample

will not be obtained. Hence, data obtained through surface sampling

ftre not generally used in this report to delineate areas of indicated 

reserves. In places, however, where the oil shale showed little effect

or weathering ana a representative sample was obtained, the analytical

data were used in the computation of indicated reserves.

An experienced investigator can estimate with moderate accuracy 

the oil content of oil shales from their physical characteristics. Esti-
OIL-SHALE RESOURCES, PICEANCE CREEK BASEST, COLORADO 261

mates tend to be conservative, and they have not been used in the

-\ calculation of indicated reserves; however, they were used in estimating 

the oil content of areas containing inferred reserves.

SUMMARY OF POTENTIAL RESERVES

The following estimates of tonnage and oil content of the oil-shale

deposits include the total amounts of oil shale in place and total

^ potential oil yield, assuming that all the oil could be extracted from

the deposit. Recoverable oil from the deposits will doubtlessly be

much less than the total potential yield of the deposits because of

losses in mining and processing and other unappraised cutoff limits

of grade, depth, or distance from outcrop of a selected shale unit that

may be exploited in the future. No attempt is made in this report

s. to estimate the amount of oil recoverable from the deposits.

Estimated tonnage and oil content of shale in that part of the 

Mahogany zone that contains an average of 45 gallons of oil per ton 

in a continuous sequence 5 feet or more thick are shown in table 1. 

Distribution and thickness of the part of the unit for which estimates 

were made are shown on plate 14, A. Approximately 261 square 

miles of the area are underlain by indicated reserves of about 6,360 million tons of such shale with an oil content of about 6,800 million 

barrels. In addition, about 27 square miles of the area contain inferred reserves of 655 million tons of oil shale with an oil content 

of about 700 million barrels.

Estimates of tonnage and oil content of the 45-gallon shale are 

made only for the southern half of the area (pi. 14, A), where 

numerous analyses of both cores and surface samples indicate fairly 

"> well the thickness of oil shale averaging 45 gallons of oil per ton. 

Except for 3 core holes in the southern part of T. 3 S., R. 99 W., and 

2 in T. 1 S., R. 100 W., there are no oil-shale samples north of the 

northern boundary of T. 4 S., that supply a basis for estimating the 

thickness of shale that yields an average of 45 gallons of oil per ton. 

Analysis of cuttings from one well hi the Piceance Creek gasfield suggests the presence of 45-gallon shale: General Petroleum Corp. well 

5-31-G, sec. 31, T. 1 S., R. 96 W., yielded one 10-foot sample in the 

Mahogany zone that assayed 43.9 gallons of oil per ton.

The thickest known sequence of 45-gallon shale (31 feet) in the 

area was obtained from the U. S. Bureau of Mines core hole E, sec. 

2, T. 5 S., R. 95 W.

* Estimates of tonnage and oil content of that part of the Mahogany 

zone and adjacent beds that yields an average of 30 gallons of oil per 

ton in a continuous sequence 15 feet or more thick are shown in table 

2; the thickness and distribution of the unit are shown on plate 14, B. 

The unit includes the 45-gallon oil shale shown in table 1. An area
262 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 1. Estimated tonnage and oil content of oil shale in part of the Mahogany 

zone that yields an average of 45 gallons of oil per ton in a continuous sequence 5 

feet or more thick

[Estimates Include the total tonnage and oil content of the deposit, but they do not indicate the amounts

recoverable]

Township and range Acreage

Average

thickness 

of oil shale

(feet)

Average

tonnage

per acre of 

oil shale

(thousands

of tons)

Average

oil yield

per acre 

(thousands

of barrels)

Tonnage of

oil shale 

(millions of

tons)

Potential

oil yield 

(millions of

barrels)

Indicated Potential Reserves

T. 4S., R. 94 W._- 

T. 4 S., R. 95 W______

T. 4 S., R. 99 W______

T. 5 S., R. 94 W._._-

T. 5 S., R. 95 W__ _ .

T. 5 S., R. 96 W.__...

T. 5 S., R. 97 W_ __ .

T. 5 S., R. 98 W._ __

T. 5 S., R. 99 W__. _

T. 6 S., R. 94 W ___ .

T. 6 S., R. 95 W_.____

T. 6 S., R. 96 W ___

T. 6 S., R. 97 W ___ .

T. 6 S., R. 98 W__ __

T. 6 S., R. 99 W______

T. 6 S., R. 100 W.....

T. 7 S., R. 96 W _ __

T. 7 S., R. 97 W ______

T. 7 S., R. 98 W ______

T 7 S R QQ W

T. 7 S., R. 100 W_____

Total __________

2,570

9,310

10, 068

17, 100

19, 410

18, 350

19, 225

9,930

2,200

647

10, 820

8,790

17, 190

6,730

2,820

59 

2,080

6, 590

1,030

2,070

119

167, 108

15

26

6

15

20

15

10

10

6

11

15

18

17

9

6

5

0

10

9

8

5

40.2

69.6

16. 1

40.2

53.6

40.2

26.8

26.8

16. 1

29.5

40.2

48.2

45.6

24. 1

16. 1

13.4 

241

OA Q

24. 1

21.4

13.4

43.0

74.5

17.2

43.0

57.4

43.0

28.7

28.7

17.2

31.6

43.0

51.6

48.8

25.8

17.2

14.3 

25.8

90 7

">c; Q

22. 9

14.3

. 103

648

162

687

1,040

738

515

266

35

19

435

424

784

162

45

.8 

50

177

OK

44

1,6

6, 361. 4

111

694

173

735

1, 114

789

552

285

38

20

465

454

839

174

49

.8 

54

1 QQ

97

47

1,7

6, 811. 5

Inferred Potential Reserves

T _l a "R Q-4. "W

T.4S.. R. 95W___ 

T. 7 S., K.. 88 W 

T.5S,,R.99-W...-«

Total....... 

9 OQA

13, 050

981

17, 151

10

16

7

7

26.8

42. 9

JLo. o

18. 8

28,7

45. 9

90 1

L\J. 1 

2O. 1

61

56O

1CloIS

655

66

599

17

20

702
OIL-SHALE RESOURCES, PICEANCE CREEK BASIN, COLORADO 263

1 TABLE 2. Estimated tonnage and oil content of oil shale in and adjacent to the Mai hogany zone that yields an average of SO gallons of oil per ton in continuous sequence 

15 feet or more thick

{Estimates include the total tonnage and oil content of the deposit, but they do not Indicate the amounts

recoverable]

Township and range Acreage

Average

of oil shale 

thickness

(feet)

Average

tonnage

per acre of 

oil shale

(thousands

of tons)

Average

oil yield

per acre 

(thousands

of barrels)

Tonnage of

oil shale 

(millions of

tons)

Potential

oil yield 

(millions of

barrels)

Indicated Potential Reserves

T 1 S R 96 W

T. 1 S., R. 99 W..._._

T. 1 S., R. 100 W __

T. 2 S., R. 99 W......

T. 2 S., R. 100 W._._.

T. 3S., R. 98 W____._

T. 3 S., R. 99 W......

T. 3 S., R. 100 W._._.

T. 4S., R. 94 W______

T. 4 S., R. 95 W......

T. 4S., R. 96 W______

T. 4 S., R. 97 W____._

T. 4 S., R. 98 W......

T. 4S..R. 99 W......

T. 4S., R. 100 W__.__

T. 5S., R. 94 W......

T. 5 S., R. 95 W......

T. 5 S., R. 96 W___-_.

T. 5 S., R. 97 W......

T. 5 S., R. 98 W......

T. 5 S., R. 99 W.__...

T. 6 S., R. 94 W_,____

T. 6 S., R. 95 W......

T. 6 S., R. 96 W______

T. 6 S., R. 97 W...._._

T. 6 S., R. 98 W.__.__

T. 6 S., R. 99 W......

T. 6 S., R. 100 W__.__

T. 7S., R. 96 W......

T. 7 S., R. 97 W......

T. 7 S., R. 98 W......

T. 7 S., R. 99 W.__-__

T. 7 S., R. 100 W._-_-

Total...... __

2,212

3,162

7,264

5,926

12, 192

4,570

20, 070

2,800

2,750

7,330

5,215

4,550

11, 392

22, 592

1,796

17, 187

19, 410

18, 350

21, 600

16, 810

13, 000

647

10, 820

8,790

17, 190

8,650

5,460

2,055

2,080

6,590

1,030

2,070

209

285, 769

30

52

35

43

35

75

51

36

60

100

88

82

65

44

29

60

QO

85

67

48

40

55

78

85

75

55

40

18

47

47

35

32

17

88.8

153.9

103.6

127.3

103 6

222.0

151.0

106.6

177.6

296.0

260. 5

242.7

192.4

130.2

85.8

177.6

266.4

251.6

198.3

142. 1

118.4

162.8

230.9

251.6

222.0

162.8

118.4

53.3

139.1

139.1

103.6

94.7

50.3

63.4

109.9

74.0

90.9

74.0

158.6

107.8

76. 1

126.9

211.4

186. 1

173.4

137.4

93.0

61.3

126.9

190.3

179.7

141.7

101.5

84.6

116.3

164.9

179.7

158.6

116.3

84.6

38.1

99.3

QQ 1

74 0

67.6

35.9

196

487

753

754

1,263

1,015

3,031

298

488

2,170

1,359

1, 104

2,192

2,941

154

3,052

5,171

4,617

4,283

2,389

1,539

105

2,498

2,212

3,816

1,408

646

110

289

Q17

107

IQfi

11

51, 571

140

348

538

539

902

725

2,165

213

349

1,550

971

789

1,566

2,101

110

2,180

3,694

3,298

3,059

1,707

1,099

75

1,784

1,580

2,726

1,006

461

79

207

655

77

140

36, 841
264 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 2. Estimated tonnage and oil content of oil shale in and adjacent to the Mahogany zone that yields an average of 80 gallons of oil per ton in continuous sequence 

15 feet or more thick Continued

Township and range Acreage

Average

of oil shale 

thickness

(feet)

Average

tonnage

per acre of 

oil shale

(thousands

of tons)

Average

oil yield

per acre 

(thousands

of barrels)

Tonnage of

oil shale 

(millions of

tons)

Potential

oil yield 

(millions of

barrels)

Inferred Potential Reserves

T. 2N., R. 97 W__.__

T. 2N.f R. 98 W...._

T. 2 N., R. 99 W. ....

T 1 N., R. 96 W__-__

T. IN., R. 97 W.-...

TIN R 98 W

T. IN., R. 99 W_____

T. 1 N., R. 100 W.._. 

T. 1 S., R. 95 W__--_.

T. 1 S., R. 96 W _ ...

T. 1 S., R. 97 W_._._-

T. 1 S., R. 98 W ___

T. 1 S., R. 99 W....__

T. 1 S., R. 100 W..,__

T. 2 S., R. 95 W ______

T. 2 S., R. 96 W______

T. 2 S., R. 97 W ______

T. 2 S., R. 98 W ____

T. 2 S., R. 99 W ______

T, 3 S., R. 94 W_____.

T. 3 S., R. 95 W ______

T. 3 S., R. 96 W_ ____

T. 3 S., R. 97 W ______

T, 6 O a., Q iv. p QO yo W W 

T. 3 S., R. 99 W._____

T. 48., R. 94 W______

T. 4 S., R. 95 W.__-_

T. 4 S., R. 96 W__

T. 4 S., R. 97 W___.__

X. 4 S., R.. 98 W _

T. 4 S., R. 99 W ...

T. 4 g., R. 100 W.....

T. 5 S., R. 99 W ___ _

T. 5 g., R. 100 W____.

T.7S,R.99W____;_

Total _____ 1__

446

8,582

3,578

3,424

18, 112

22, 920

20, 288

445 

565

20, 384

28, 320

24, 860

22, 038

2,246

7,050

23, 400

23, 925

23, 450

17, 783

579

18, 420

23, 477

24, 210

19, 264

1,594

5,020

15, 290

17, 025

18, 750

208

: 3,(B3

3, 11O

993 640

- 1,460 '

436, 149

20

25

21

25

45

64

36

17 

17

90

79

69

56

25

25

35

72

61

50

22

32

51

74

72

54

40

80

77

78

75

23

19

20

16

20

59.2

74.0

62.2

74.0

133.2

189.4

106.6

50.3 

50.3

266.4

233.8

204.2

165.8

74.0

74.0

103.6

213. 1

180. 6

148.0

65.1

94.7

151.0

219. 0

213. 1

159.8

118.4

236.8

227.9

230.9

999 O

68. 1

56,2

50. 2

47.4

59,2

42.3

52.9

44.4

52.9

95. 1

135.3

76.1

35.9 

35.9

190.3

167.0

145.9

118.4

52.9

52.9

74.0

152. 2

129. O

105.7

46.5

67.7

107. 9

156. 4

152.2

114.1

84.6

169. 1

162.8

164. 9

1 CO R

40.1

42 3

33.9

52. 9 

4.2,3

26

635

223

253

2,413

4,341

2,163

22

28

5,430

6,621

5,076

3,654

166

522

2,424

5,098

4, 235

2,632

38

1,744

3, 545

5,302

4, 105

255

594

3,621

3,880

4,329

2 A9S

170

184

11

bl

80

76, 529

19

454

159

181

1,724

3, 101

1,545

16 

20

3,879

4,729

3, 626

2,610

119

373

1,731

3,641

3,025

1,880

27

1,246

2, 532

3,787

2,932

182

424

2,587

2,771

5,092

1 877

121

8

43

01

54, 663
OIL-SHALE RESOURCES, PICEANCE CREEK BASIN, COLORADO 265

of approximately 447 square miles contains indicated reserves of about 

52,000 million tons of shale with a potential yield of about 37,000 

million barrels of oil. In addition, approximately 683 square miles 

contain inferred reserves of about 76,000 million tons of shale with a 

potential yield of about 54,000 million barrels of oil.

General Petroleum Corp. weU 22-3-G, in sec. 3, T. 2 S., R. 96 W., 

contains 130 feet of shale in a continuous sequence that will yield an 

average of 30 gallons of oil per ton.

Other oil-shale zones yielding 30 gallons of oil per ton, not shown on 

the thickness maps, occur below the Mahogany zone. They range 

from 340 to 1,520 feet below the top of the Mahogany bed and are 

known only in the northeastern part of the basin in the vicinity of 

the Piceance Creek gasfield, where limited information is available 

from analyses of well cuttings. These zones combined cover an estimated area of 91 square miles and contain inferred reserves of about 

9,500 million tons of shale with a potential yield of about 6,800 million 

barrels of oil. The maximum known thickness of 30-gallon shale is 

180 feet; it is in a zone 830 feet below the Mahogany zone in General 

Petroleum Corp. well 5-31-G, located in sec. 31, T. 1 S., R. 96 W.

Total indicated and inferred reserves of about 137,500 million tons 

of 30-gallon-per-ton shale with a minimum thickness of 15 feet are 

present in the area. These reserves have a potential oil yield of 97,800 

million barrels.

Estimated tonnage and oil content of that part of the Mahogany 

zone and adjacent beds that yield an average of 25 gallons of oil per 

ton in a continuous sequence 15 feet or more thick are shown in table 3; 

the distribution and thickness of the unit are shown on plate 14, C. 

The unit includes the 30-gallon shale shown in table 2. Indicated 

reserves of about 93,000 million tons of shale that contain about 55,000 

million barrels of oil underlie an area of 452 square miles. Inferred 

reserves totaling about 167,000 million tons of shale that contain 

about 100,000 million barrels of oil underlie an additional 751 square 

miles. The thickest sequence of 25-gallon shale in the unit is found 

in General Petroleum Corp. well 5-31-G, in sec. 31, T. 1 S., R. 96 W., 

where it attains a thickness of 220 feet.

There are several zones that are not shown on the thickness maps, 

in the oil-shale sequence below the Mahogany zone, that contain an 

average of 25 gallons of oil per ton hi a continuous sequence 15 feet 

or more thick. These zones are known only from assays of rotary 

cuttings in the vicinity of the Piceance Creek dome. As far as is 

known, they underlie about 180 square miles and contain inferred 

reserves of about 65,000 million tons of oil shale with an oil content of 

about 39,000 million of barrels. The thickest known sequence of 

25-gallon shale is in General Petroleum Corp. well 5-31-G, in sec.
266 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 3. Estimated tonnage and oil content of oil shale in and adjacent to the 

Mahogany zone that yields an average of 25 gallons of oil per ton in a continuous 

sequence 15 feet or more thick

[Estimates Include the total tonnage and oil content of the deposit, but they do not indicate the amounts

recoverable]

Township and range Acreage

Average

thickness 

of oil shale

(feet)

Average

tonnage

per acre of 

oil shale

(thousands

of tons)

Average

oil yield

per acre 

(thousands

of barrels)

Tonnage of

oil shale 

(millions of

tons)

Potential

oil yield 

(millions of

barrels)

Indicated Potential Reserves

T. 1 N., R. 96 W._.-_

T. 1 S., R. 95 W._-_ 

T. 1 S., R. 96 W ______

T. 1 S., R. 99 W 

T. 1 S., R. 100 W. __

T. 2 S., R. 99 W_-__.

T. 2 S., R. 100 W____.

T. 3 S., R. 98 W-_--_-

T. 3 S., R. 99 W._____

T. 3 S., R. 100 W_-__

T. 4 S., R. 94 W 

T. 4 S., R. 95 W .._

T. 48., R. 96 W____._

T. 4 S., R. 97 W ___

T. 4 S., R. 98 W __.

T. 4S., R. 99W--__. 

T. 48., R. 100 W-__ 

T. 5 S., R. 94 W______

T. 5 S., R. 95 W

T. 5 S., R. 96 W......

T. 5 S., R. 97 W __ __

T. 5 S., R. 98 W _ _

T. 5 S., R. 99 W_ ..

T. 6 S., R. 94 W

T.6S.,R.95W ...

T. 6 S., R. 97 W......

T, 0 &,, R, 92 W......

T. 6 S., R. 99 W 

T. 6 S., R. 100 W. ____

T 7 S R 96 W

T. 7 S., R. 97 W __ _

T.7S,R.98W ...

T, 7 S,, R, 100 W.....

Total _ .-.__- -

134

104

3,495

3, 162

7,264

5,926

12, 192

4,570

20, 070

2, 800

3,020

7,330

5,215

4, 550

11, 392

22, 592 

1,796

18, 131

19 410

18, 350

21, 600

16, 81O

13,000

647

10, 820

17, 190

8,650

5,460

2,560

2,080

6, 590

1,030

538

289, 338

17

18

30

101

65

90

70

130

98

65

80

150

140

145

95

85 

45

90

150

140

120

100

70

80

120

130

95

75

30

80

90

85

25

52.2

55.3

92. 1

310. 1

1QQ fi

276.3

214.9

399. 1

300.8

199.6

245.6

460.5

429.8

445. 2

291. 7

261.0 

138. 1

276.3

460. 5

429.8

368. 4

3O7. O

214.9

245. 6

368.4

399.1

291,7

230.3

92. 1

245.6

276. 3

261.0

23 O- 3

TZ O 7o, 8

31. 1

32. 9

54.8

184.6

118.8

164. 5

127.9

237.5

179.0

118.8

146.2

274. 1

255. 8

265.0

173. 6

155.3 

82.2

164.5

274. 1

255.8

219. 3

182. 7

127.9

146. 2

219.3

237.5

173,0 

137. 1

54.8

146.2

164. 5

155.3

137. 1

45.7

7

6

322

980

1,450

1,637

2,620

1,824

6,037

559

742

3,375

2,241

2, 026

3,323

5,897 

248

5,010

8,938

7,887

7, 957

5, 161

2,794

159

3,986

6,861

2,523

1,257

236

511

1, 821

269

4.77

41

92, 825

4

3

192

583

863

974

1,559

1,086

3,593

333

442

2, 009

1,334

1, 206

1,978

3,510 

148

2,982

5,320

4,694

4, 736

3, 072

1,663

OK

2,372

4,084

1,502

748

141

304

1,084

160

284

25

55, 251
OIL-SHALE RESOURCES, PICEANCE CREEK 'BASIN, COLORADO 267

TABLE 3. Estimated tonnage and oil content of oil shale in and adjacent to the 

Mahogany zone that yields an average of 25 gallons of oil per ton in a continuous 

sequence of 15 feet or more thick Continued

Township and range Acreage

Average 

thickness 

of oil shale

(feet)

Average

tonnage 

per acre of 

oil shale

(thousands

of tons)

Average

oil yield 

per acre 

(thousands

of barrels)

Tonnage of 

oil shale 

(millions of

tons)

Potential 

oil yield 

(millions of

barrels)

Inferred Potential Reserves

T 2N., R. 97 W..._.

T. 2N., R. 98 W..._.

T. 2 N., R. 99 W_____

T 1 N., R. 96 W__._.

T. 1 N., R. 97 W...._

T. 1 N., R. 98 W..._.

T. 1 N., R. 99 W_____

T. 1 N., R. 100 W____ 

T. 1 S., R. 95 W______

T. 1 S., R. 96 W_ __ _

T. 1 S., R 97 W_._ ...

T. 1 S., R. 98 W ...

T. 1 S., R. 99 W. _ ._

T. 1 S., R. 100 W..._.

T. 2 S., R. 95 W______

T. 2 S., R. 96 W......

T. 2 S., R. 97 W__.___

T. 2 S., R. 98 W. _ _.

T. 2 S., R. 99 W......

T. 3 S., R. 95 W______

T. 3 S., R. 96 W._.__.

T. 3 S., R. 97 W......

T. 3 S., R. 98 W......

T. 3 S., R. 99 W__.__.

T. 4 S., R. 94 W......

T. 4 S., R. 95 W......

T. 4 S., R. 96 W......

T. 4S., R. 97 W __ ..

T. 4 S., R. 98 W......

T. 4S., R. 99 W______

T. 4 S., R 100 W....._

T. 5 S., R. 99 W______

T. 5 S., R. 100 W_..._

T. 6 S., R. 100 W_____

T. 7 S., R. 98 W______

T. 7 S., R. 99 W......

T. 7 S., R. 100 W_____

T. 8 S., R. 99 W______

Total __________

1,488

13, 152

6,272

4,448

19, 872

22, 920

22, 756

1,440 

2,080

20, 384

28, 320

24, 860

22, 038

2,246

12, 480

23, 400

23, 925

23, 450

17, 783

19, 100

23, 477

24, 210

19, 264

1,594

3,935

15, 290

17, 025

18, 750

11, 840

208

11, 072

3,110

9,050

4,025

830

1,995

1,999

865

480, 953

30

60

40

40

70

162

85

30 

25

120

195

165

118

38

35

90

145

140

112

50

125

145

125

112

45

142

140

150

122

32

27

37

25

20

60

40

20

20

________

92.1

184.2

122.8

122. 8

214.9

497.3

261.0

122.8 

76.8

368.4

598.7

506.6

371. 5

107.5

107.5

276. 3

445.2

429. 8

334.6

153. 5

383.8

445.2

383.8

343.8

138.2

435.9

429.8

460. 5

374.5

98.2

82.9

113.6

76.8

61.4

184.2

122. 8

61.4

61.4

________

54.8

109.6

73. 1

73.1

127.9

296.0

155.3

73. 1 

45.7

219.3

356.3

301.5

221. 1

64.0

64.0

164.5

265.0

255.8

1QQ 9

QI 4

228.4

265.0

228.4

204.6

82.3

OKQ C

255.9

274. 1

999 Q

58.5

49.4

67.7

45.7

36.6

10Q 7

70 i

36.6

36.6

________

137

2,423

770

546

4,270

11,398

5,939

177 

16

7,509

16, 955

12, 594

8,187

241

1,342

6,465

10, 651

10 07Q

5,950

9 Q39

9,011

10, 778

7 3Q4

KAC

544

6,665

7,317

8,634

4. 434

20

QIC

353

«QC

247

1 CO

245

CO

166, 713

81

1,442

458

325

2,541

6,784

3,535

105 

9

4,469

10, 092

7,496

4,873

143

799

3,848

6,339

5,999

3,541

1,745

5,363

6,415

4,401

326

324

3,967

4,355

5, 139

2,639

12

546

210

414

147

91

146

73

32

99, 233
268 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 4. Estimated tonnage and oil content of oil shale that yields an average 

of 15 gallons of oil per ton in continuous sequence 15 feet or more thick

[Estimates Include the total tonnage and oil content of the deposit, but they do not indicate the amounts

recoverablel

Township and range Acreage

Average 

thickness 

of oil 

shale 

(feet)

Average 

tonnage of 

oil shale 

per acre 

(thousands 

of tons)

Average 

oil yield 

per acre 

(thousands 

of barrels)

Tonnage of Potential 

oil shale | oil yield 

(millions of ! (millions 

tons) !of barrels)

i

Indicated Potential Reserves

T. 2 N., R. 98 W-.-__

T. 1 N., R. 96 W__.__

T. 1 N., R. 98 W____.

T. 1 N., R. 99 W..._.

T 1 S R Q5 W

T. 1 S., R. 96 W__.__-

T. 1 S., R. 97 W.____.

T. 2 S., R. 95 W_____.

T. 2 S., R. 96 W__ __

T. 2 S., R. 97 W_..___

T. 2 S., R. 99 W______

T. 2 S., R. 100 W_____

T. 3 S., R. 94 W _

T. 3 S., R 95 W _

T. 3 S., R. 96 W

T. 3 S., R. 99 W_ _ __

T. 3 S, R. 100 W.....

T. 4 S., R. 94 W_ _ ._

T. 4 S, R. 95 W _._

T. 4 S., R. 96 W..._._

T. 4 S., «.. 07 W

T. 4 S., R. 98 W _ _

T. 4 S., R. 99 W ______

T. 4 S., R. 100 W__.._

T. 5 S., R. 94 W..___-

T. 5 S., R. 95 W._____

T. 5 S., R. 96 W_.___-

T. 5 S., R. 97 W._ ____

T. 5 S., R. 98 W. 

T. 5 S., R. 99 W._____

T. 6 S., R. 94 W __

T. 6 S., R. 95 W._____

T. 6 S., R. 96 W__.__.

T. 6 S., R. 97 W._ __

T. 6 S., R. 98 W______

T. 6 S., R. 99 W _ _

X, 6 S., R. 100 W _____

T. 7 S., R. 98 W._.__.

T. 7 S., R. 99 W_.___.

T. 7 S., R. 100 W.. 

Total... _______

535

1,250

7, 104

148

294

965 

3.860

7,430 

2,825

16, 450

20, 400

1,325

768

8,584

580

8, 455

864 

1,427

10, 825

3,170

7, 100

7,330

5, 215

2,465

3, 950

21, 914

1,952

18, 265

20. 950

20, 610

21,610

19, 45O

13, 568

684

10, 320

9,850

14, 790

11,990

7, 780

2,945

970

2,100

717

323, 784

1,575

100

2,000

1,725

175

60 

300

1,700 

2, 150

300

1,950

2, 050

550

275

50

450

150 

1,500

700

350

180

1, 150

1,300

850

650

450

400

760

930

910

475

450

5fiO

625

630

525

400

250

400

325

175

5, 181. 8

329. 0

6, 580. 0

5, 675. 3

575. 8

197.8 

986.8

5, 593. 0 

7, 073. 5

987. 0

6, 415. 5

6, 744. 5

1, 809. 5

904. 8

164. 5

1, 480. 5

493. 5

4, 935. 0

2, 303. 0

1, 151. 5

592. 3

3, 783. 5

4. 277, 1

2, 796. 5

2, 138. 5

1, 480. 5

1, 316. 0

2, 500. 4

3,059.7

2, 993. 9

1, 562. 8

1, 481. 0

1, 842, 4

2, 056. 2

2, 072. 7

1, 727. 3

1, 316. 0

822. 5

1, 316. 0

1, 069. 0

576.0

1, 850. 4

117.5

2, 349. 7

2, 026. 6

205. 6

70. 6

352.4

1. 997. 3 

2, 525. 9

352. 5

2, 291. 0

2, 408. 5

646.2

323. 1

58. 7

528. 7

176. 2

1, 762. 3

C9*> A

411.2

211. 5

1, 351. 1

1, 527. 3

998. 6

763. 7

528.7

469.9

892.9

1, 092. 6

1. 069. 1

763. 7

558.1

528. 9

657. 9

734.3

740. 2

616.8

469 9

293. 7

469.9

381. 7

205.7

2,772

41!

46, 74-1

840

169

191

3, 80!)

41,556 

19, 983

16, 236

130, 876

8, 936

1, 390

7, 767

95

12,518

426

7,042

24, 930

3,650

4, 205

19, 731

10, 543

11, 046

46, 863

2,890

24, 037

52, 383

63. 060

64, 698

4.1 ^Q4.

21, 204

1, 013

19,014

20, 254

30, 655

20, 710

1 fi OQQ

2, 423

1,277

2, 245

413

818, 200

990

147

16, 693

300

60

68 

1,361

14, 840 

7, 136

5, 798

46. 736

3, 191

496

2,774

34

4, 470

152

2,515

8 QHQ

1.303

1.502

e

f\f\f\

7,046

3,765

3

Q_i_K

16. 735

1,032

8, 584

18, 706

22, 519

23, 104

14, 853

7,572

362

6. 790

7,233

10, 947

7,395

3

CKC

865

456

802

147

292, 183
OIL-SHALE RESOURCES, PICEANCE CREEK BASIN, COLORADO 269

TABLE 4. Estimated tonnage and oil content of oil shale that yields an average 

of 15 gallons of oil per ton in continuous sequence 15 feet or more thick Con.

Township and range Acreage

Average

thickness

of oil

shale

(feet)

Average

tonnage of

oil shale

per acre

(thousands

of tons)

Average

oil yield

per acre

(thousands

of barrels)

Tonnape of

oil shale

(million? of

tons)

Potential

oil yield

(millions

of barrels)

Inferred Potential Reserves

T. 2N., R. 97 W.____

T. 2 N., R. 98 W-. _

T. 2N..R. 99 W.____ 

T. 2 N., R. 100 W __ 

T. 1 N., R. 96 W.____

T. 1 N., R. 97 W._... 

T. 1 N., R. 98 W..._.

T. 1 N., R. 99 W..._. 

T. 1 N., R. 100 W____ 

T. 1 S., R. 95 W.._._.

T. 1 S., R. 96 W.__._.

T. 1 S., R. 97 W______

T. 1 S., R. 98 W._ _ .

T. 1 S., R. 99 W._ _ .

T. 1 S., R. 100 W._...

T. 2 S., R. 95 W._____

T. 2 S., R. 96 W._.__.

T. 2 S., R. 97 W___.__

T. 2 S., R. 98 W._____

T. 2 S., R. 99 W..._._

T. 2 S., R. 100 W...._

T. 3S., R. 94 W___.__

T. 3 S., R. 95 W._ __

T. 3 S., R. 96 W __ .

T. 3 S., R. 97 W______

T. 3 S., R. 98 W. ___

T. 3 S., R. 99 W._____

T. 4 S., R 94 W ___

T. 4S., R. 95 W._ __

T. 4 S., R. 96 W ___

T. 4 S., R. 97 W. ___

T. 4 S., R. 98 W__ __

T. 4 S., R. 99 W______

T. 4 S., R. 100 W. __

T. 5 S., R. 97 W. __ .

T. 5 S., R. 98 W. _ __

T. 5 S., R. 99 W.. __

T. 5 S., R. 100 W_.___

T. 6 S., R. 95 W__ __

T. 6 S., R. 96 W._ __

2,445

14,272

10, 570 

211 

9,410

20, 950 

16. 256

23, 002 

4,320 

8,090

13, 350

25, 495

24, 860

25, 200

17, 700

3,485

3, 355

22, 600

23, 450

22, 232

4,516

160

14, 000

22, 050

24, 210

23, 550

11,428

3,600

15, 290

17, 025

20, 750

18, 510

256

12, 898

1, 190

743

5,527

18, 410

1,010

1.804

200

675

200 

20 

150

900 

2,025

950 

225 

80

1,000

2,050

1,975

1, 150

225

50

1,850

1,775

1,575

1,050

250

20

600

1,600

1,500

1,250

975

150

700

1,200

1,250

1,000

450

350

975

850

350

200

575

590

658. 0

2, 220. 8

658.0 

65.8 

493.5

2, 961. 0 

6. 662. 3

3, 125. 5 

740.3 

263. 2

3, 290. 0

6, 744. 5

6, 498. 7

3, 783. 5

740.3

164.4

6, 086. 4

5, 839. 8

5 1 Q1 7

3, 454. 5

822.5

65.8

1. 974. 0

5, 264. 0

4, 935. 0

4, 112. 5

3, 208. 7

493.5

9 ^fli n

3, 948. 0

4, 112. 5

3, 290. 0

1,480.5

1, 151. 5

3, 207. 6

2, 796. 8

1,151.5

658.0

1, 892. 1

1.941.2

235. 0

793.0

235. 0 

23.5 

176.2

1, 057. 4 

2, 379. 1

1, 1 16. 1 

264.4 

04 n

1 174. Q

2, 408. 5

2. 320. 7

1, 351. 1

264.4

58.7

2, 173. 5

2, 085. 4

1, 850. 4

1, 233. 6

OOQ 7

23.5

704. 9

1, 879. 8

1, 762. 3

1, 468. 6

1, 145. 9

176.3

822.4

1 40Q Q

1, 468. 6

1 174 9

528.7

411.2

1, 145. 5

one o

411.2

235.0

675.7

693. 3

1. 609

31, 695

6, 955 

14 

4,644

62. 033 

108, 302

71,893 

3,198 

2 129

43, 922

171,951

161, 558

95, 344

13, 103

573

20, 420

131, 979

121,511

76, 800

3,714

11

27, 636

116,071

119 476

96, 849

36, 669

1,777

oc 91 o

67, 215

QC QQ4

60^ 898

379

14, 852

3.817

2,078

6, 364

12. 114

1 Q1 1

3.502

575

11, 318

2,484 

5 

1,658

22, 152 

38, 675

25, 673 

1,142 

760

15, 685

61, 404

57, 692

34, 047

4 67Q

90^

7,292

47 1^0

40 OQI

27, 425

1 QOA

4

9,869

41, 449

42, 665

34, 585

13,094

aoe

19 ^7^

94 flO9

30, 473

21, 747

10K

5,304

1,363

742

2,273

4

qofi

683

1.251
270 CONTRIBUTIONS TO ECONOMIC . GEOLOGY

TABLE 4. Estimated tonnage and oil content of oil shale that yields an average 

of 15 gallons of oil per ton in continuous sequence IB feet or more thick Con.

Township and range

T. 6 S., R. 97 W______

T. 6 S., R. 100 W__-__

T. 6 S., R. 101 W___._

T. 7 S., R. 96 W-____.

T. 7 S., R. 97 W_.._._

T. 7 S., R. 98 W_.____

T. 7 S., R. 99 W_____.

T. 7 S., R. 100 W_.___

T. 7 S., R. 101 W__ __

T. 8 S., R. 99 W._.___

T. 8 S., R. 100 W__.__

Total.. .__...__

Acreage

5, 100

7,580

4,710

4,140

9, 550

2,320

3,070

9,000

2, 175

2,250

1,120

559, 195

Average 

thickness 

of oil 

shale 

(feet)

510

150

85

425

425

325

200

100

55

150

90

Average 

tonnage of 

oil shale 

per acre 

(thousands 

of tons)

1, 677. 8

493.5

279.7

1, 398, 3

1, 398. 3

1, 069. 4

658.0

329.0

181. 1

493.5

296.1

Average 

oil yield 

per acre 

(thousands 

of barrels)

599.2

176.3

99.9

499,4

499.4

381. 9

235. 0

117. 5

64. 7

176.3

105.8

Tonnage of 

oil shale 

(millions of 

tons)

- 8,557

3,741

1,317

5,789

13, 354

2,481

2,020

2,961

394

1,110

332

1, 867. 569

Potential 

oil yield 

(millions 

of barrels)

3,056

1,336

471

2,067

4,769

886

721

1,057

141

396

119

666, 911

31, T. 1 S., R. 96 W., where it is 780 feet thick and lies 500 feet below 

the Mahogany bed.

Indicated and inferred reserves of 25-gallon-per-ton shale total 

about 325,000 million tons with an oil content of 194,000 million 

barrels.

Estimates of tonnage and oil content of that part of the Green River 

formation that yields an average of 15 gallons of oil per ton in a continuous sequence 15 feet or more thick are shown in table 4. The 

distribution and thickness of 15-gallon shale are shown on plate 14, D. 

This unit includes the oil shales of all units previously discussed,

Approximately 506 square miles of the area contain indicated reserves

of about 818,000 million tons of oil shale with an oil content of 292,000

million barrels. An additional area of approximately 874 square miles

contains inferred reserves of about 1,868,000 million tons of oil shale 

with an oil content of 667,000 million barrels. Analyzed rotary samples from General Petroleum Corp. well 5-31-G, sec. 31, T. 1 S., R.

96 W., just 10 miles west of the eastern 15-foot cutoff line (pi. 14, D), 

indicate the presence of an oil-shale sequence 2; 200 feet thick that

will yield an average of more than 15 gallons of oil per ton.
OIL-SHALE RESOURCES, PICEANCE CREEK BASEST, COLORADO 271 

LITERATURE CITED

Belser, Carl, 1951, Green River oil-shale reserves of northwestern Colorado:

U. S. Bur. Mines Rept. Inv. 4769, 21 p. 

Bradley, W. H., 1931, Origin and microfossils of the oil shale of the Green River

formation of Colorado and Utah: U. S. Geol. Survey Prof. Paper 168, 58 p. 

Cadman, W. H., 1948, The oil shale deposits of the world and recent developments

in their exploitation utilization reviewed to May 1947, p. 109-133. 

Donnell, J. R., Cashion, W. B., Jr., and Brown, J. H., Jr., 1953, Geology of the

Cathedral Bluffs oil-shale area, Rio Blanco and Garfield Counties, Colo.:

U. S. Geol. Survey Oil and Gas Inv. OM 134. 

Duncan, D. C., and Belser, Carl, 1950, Geology and oil-shale resources of the

eastern side of the Piceance Creek basin, Rio Blanco and Garfield Counties,

Colo.: U. S. Geol. Survey Oil and Gas Inv. OM 119. 

Duncan, D. C., and Denson, N. M., 1950, Geology and oil-shale reserves of Naval

Oil-Shale Reserves Nos. 1 and 3, Garfield County, Colo.: U. S. Geol. Survey

Oil and Gas Inv. Prelim. Map 94. 

Guthrie, Boyd, 1955, Technological developments in retorting Colorado oil shale,

1944-1954: Fourth World Petroleum Gong. Proc. section III/H. 21 p.,

Carlo Colombo, Rome, Italy. 

Guthrie, Boyd, and Klosky, Simon, 1951, The oil-shale industries of Europe:

U. S. Bur. Mines Rept. Inv. 4776. 

Lutz, K., 1938, The occurrence and application of Kukersite in Estonia, with

particular reference to the plant of the A/G "Esimene Eesti Polevkivitoostus"

(First Estonian oil shale industry): London, Inst. Petroleum, p. 124-142. 

Stanfield, K. E., Frost, I. C., McAuley, W. S., and Smith, H. N., Properties of

Colorado oil shale: U. S- Bur. Mines Rept. Inv. 4825, 1951, 27 p. 

Waldrou, F. R., Donnell, J. R., and Wright, J. C., 1951, Geology of the De Beque

oil-shale area, Garfield and Mesa Counties, Colo.: U. S. Geol. Survey Oil and

Gas Inv. OM 114. 

Winchester, D. E., 1917, Oil shale in northwestern Colorado and adjacent areas:

U. S. Geol. Survey Bull. 641-F, p. 139-198. 

 1923, Oil shale of the Rocky Mountain region: U. S. Geol. Survey Bull.

729, 204 p.

o