Estimates of the Potential 

Petroleum Resources in 

Wilderness Lands 

By Betty M. Miller 

PETROLEUM POTENTIAL OF WILDERNESS LANDS IN THE 

WESTERN UNITED STATES 

G E 0 L 0 G I C A L S U A V E Y C I A C U LA A 9 a· 2 - P 

CONTENTS 

Page 

Abstract---------------------------------------------------------------------- P1 

Introduction------------------------------------------------------------------- 1 

Results of qualitative petroleum analysis ------------------------------------------- 2 

Petroleum potential maps----------------------------------------------------- 3 

Results of quantitative petroleum analysis------------------------------------------ 4 

Summary--------------------------------------------------------------------- 13 

Referencecited ---------------------------------------------------------------- 15 

ILLUSTRATIONS 

Page 

FIGURE 1. Index map of Wilderness Lands study area listing identification for USGS Miscellaneous Investigations Series 

Maps to be published showing petroleum potential for Wilderness Lands at a scale of 1:1,000,000---------- P4 

2-12. Undiscovered recoverable [oil and gas] resources in Wilderness Lands in: 

2.Arizona ---------------------------------------------------------------------------------- 5 

3.California -------------------------------------------------------------------------------- 5 

4.Colorado---------------------------------------------------------------------------------- 6 

5.Idaho ------------------------------------------------------------------------------------ 6 

6.Montana --------------------------------------------------------------------------------- 7 

7.Nevada----------------------------------------------------------------------------------- 7 

8. New Mexico-------------------------------------------·------------------------------------ 8 

9.0regon----------------------------------------------------------------------------------- 8 

10. Utah------------------------------------------------------------------------------------- 9 

11. Washington------------------------------------------------------------------------------- 9 

12. Wyoming--------------------------------------------------------------------------------- 10 

13. Total undiscovered recoverable [oil and gas] resources in Wilderness Lands in 11 Western States ------------- 11 

14. Total undiscovered recoverable [oil and gas] resources in the 38 USGS petroleum provinces in which Wilderness 

Lands are located that were included in this study------------------------------------------------ 11 

TABLES 

Page 

TABLE 1. Petroleum potential by acreage for all Wilderness Land categories in the Western United States-------------- P2 

2. Petroleum potential by acreage for all Wilderness Lands in the Western United States by controlling Federal 

agency------------------------------------------------------------------------------------ 3 

3. Petroleum potential in Wilderness Lands by State in Western United States------------------------------ 12 

4. Statistics on the distribution ofWilderness Lands in the Western United States---------------------------- 13 

III 
PETROLEUM POTENTIAL OF WILDERNESS LANDS IN THE WESTERN UNITED STATES 

Estimates of the Potential Petroleum Resources 

in Wilderness Lands 

By Betty M. Miller 

ABSTRACT 

The estimates of the potential petroleum resources for the 

Wilderness Lands in the 11 Western States were conducted in 

two distinct and separate phases for this study: the qualitative 

analysis and the quantitative analysis. The analysis of the 

geologic characteristics favorable or unfavorable for the occurrence of recoverable oil and gas resources for all the Wilderness Lands provided the input used by the geologists to subjectively determine the qualitative estimates of the petroleum 

resources for each tract and also provided the basic input for 

the subjective estimates for the quantitative analysis. 

A gradational rating scale was assigned by the geologists to 

each wilderness tract and included the following categories of 

potential: high, medium, low, low to zero, zero, and unknown. 

A summary of the total wilderness acreages compiled according to their respective estimated petroleum potentials shows: 

at least 34 percent of the total 74 million acres of Wilderness 

Lands have the geologic characteristics necessary for the occurrence of petroleum resources in varying amounts (high, 

medium, and low); an additional 33 percent of the Wilderness 

~ands may have some small potential, but is more likely to fall 

m the low to zero potential and the unknown categories; and 

33 percent of the total acreage of the Wilderness Lands probably has no petroleum potential because it is located in predominately igneous and (or) metamorphic terrane. 

The qualitative petroleum potential for all the Wilderness 

Lands is also being published as color-coded maps in the USGS 

P1 

Miscellaneous Investigations Series Maps (1-1537 through 1-

1547, in press) for each of the Western States at a scale of 

1:1,000,000. 

The quantitative resource estimates for oil and natural gas 

for the Wilderness Lands are expressed as probability distributions for the individual States and aggregated totals for the 

11 Western States. The total undiscovered recoverable oil for 

the Wilderness Lands in the Western States is estimated to 

range from more than 0.555 to 1.490 billion barrels with a 

mean estimate of 0.834 billion barrels. The undiscovered recoverable natural gas is estimated to range from more than 5.536 

to 16.639 trillion cubic feet with a mean estimate of 9. 729 trillion cubic feet. The ranges are reported at the 95 and 5 percent 

probability levels. 

INTRODUCTION 

The petroleum resource assessments for the 

Wilderness Lands in the 11 Western States were 

conducted in two distinct and separate phases for 

this study. These two phases are referred to as 

the qualitative analysis and the quantitative analysis of the potential petroleum resources. The 

products and results of these two analyses are discussed separately below. 
RESULTS OF QUALITATIVE 

PETROLEUM ANALYSIS 

The geologic analysis for characteristics favorable or unfavorable for the occurrence of recoverable oil and gas resources for all the Wilderness 

Lands provided the input used by the geologists 

to subjectively determine the qualitative estimates of the petroleum resources for each tract. 

Using a simplification of the gradational rating 

scale, the geologists assigned one of. six classes 

(high, medium, low, low to zero, zero, and unknown) to designate the probable petroleum potential· in each tract.· The potential petroleum resource categories can be tabulated by the total 

acreages for each wilderness tract. These tabulations are made for the Wilderness Lands by petroleum province, by State, and for the total Wilderness Lands in the 11 Western States. Table 1 

shows a summary by State of the total wilderness 

acreages compiled according to their respective 

estimated petroleum potentials by category-ratings and the total acreages for each petroleum potential category for the 11 States. 

A simplification of the figures shown in table 1 

is summarized in the following manner relative to 

the ge9logic favorability for potential petroleum 

resources: 

High potential.-Approximately 4 percent of 

the total acreage in Wilderness Lands in the 

Western United States has a high potential. 

Medium potential.-At least 8 percent of the 

total acreage in Wilderness Lands has a medium 

or possibly higher potential. 

Low potential.-N early 22 percent of the total 

acreage in Wilderness Lands has potential for petroleum resources; these areas are classified with 

at least a low potential until more is known about 

the geology. 

Low to zero potential.-At least 28 percent of 

the total acreage of the Wilderness Lands consists 

of small sedimentary areas mixed within igneous 

and metamorphic terrane that may have some 

small and scattered potential but most likely a 

very low to zero overall petroleum potential. 

Zero potential.-Thirty-three percent of the 

total acreage of the Wilderness Lands occur in 

igneous and metamorphic terranes that probably 

have no potential for petroleum occurrence. 

Unknown potential.-In almost 5 percent of the 

total acreage of the Wilderness Lands not enough 

is known of the subsurface geology to make any 

iudgment on the favorability of the lands for petroleum potential. 

At least 34 percent of the total acreage for Wilderness Lands, or approximately 25 million acres, 

TABLE !.-Petroleum potential1 by acreage for all Wilderness Land categoriesl in the Western United States 

Petroleum potential in thousands of acres 

State Total 

High Medium Low Low-Zero Zero Unknown8 

Arizona 0 192.0 1,375.3 3,528.8 1,087.8 0 6,183.8 

California 0 36.5 1,310.2 10,249.3 7,252.6 0 18,848.6 

Colorado 140.2 94.8 819.4 0 2,445.3 1,001.4 4,501.1 

ldaho 115.1 63.4 804.7 1,023.7 5,515.6 36.7 7,559.2 

Montana 1,374.2 1,154.8 1,325.9. 1,212.2 1,825.4 38.2 6,930.7 

Nevada 132.4 1,099.1 3,631.2 0 3,117.9 0 7,980.6 

New Mexico 96.6 115.3 1,237.3 158.0 1,069.6 0 2,676.8 

Oregon 0 138.2 2,869.7 1,857.9 0 0 4,865.8 

Utah 208.9 2,638.3 1,010.4 0 625.2 0 4,482.8 

Washington 0 0 952.4 2,940.5 0 0 3,892.9 

Wyoming 661.8 391.8 723.3 19.0 1,759.3 2,451.8 6,007.0 

Total 2,729.2 5,924.2 16,059.7 20,989.4 24,698.7 3,528.1 73,928.34 

'Petroleum potential: The geologists evaluated the geological characteristics for the favorability of the occurrence of oil and natural gas and assigned a qualitative rating 

for the potential for petroleum resources, such as high, medium, etc. 

'The Wilderness Lands included in this study are identified under the following categories: Designated Wilderness, Administratively Endorsed as Suitable (prior to July 

1981), Further Planning or Study Areas, BLM Lands Under Appeal, BLM Wilderness Inventory Not Completed, and U.S. Forest Service RARE II under litigation in California. These lands are administered under four agencies: Bureau of Land Management (BLM), U.S. Forest Service (USFS), National Park Service (NPS), and Fish and 

Wildlife Service (FWS). 

'Unknown Potential: The rating of unknown is used in some wilderness areas where the geology is almost completely unknown or not enough information is available 

currently for the geologist to make any judgment on the favorability of the area for petroleum potential. 

'Total acre~ge for Wilderness Lands is the same as in table 2. All tabulated values are rounded numbers; therefore values may not be precise beyond decimal. 

P2 
may have the geologic characteristics necessary 

for the occurrence of petroleum resources in varying amounts (high, medium, and low potential). 

An additional 33 percent of the total acreage of 

the Wilderness Lands may have some small potential, but is more likely to fall in the low to zero potential and in the unknown categories. Finally, 33 

percent of the total acreage of the Wilderness 

Lands probably has no petroleum potential because the lands are located in terranes with 

predominantly igneous and (or) metamorphic 

rocks in which petroleum has rarely been found. 

The total acreage analyzed in this study for the 11 

Western States is 7 4 million acres. 

Table 2 shows a summary of the petroleum potential by acreage for all the Wilderness Land 

categories in the Western United States by the 

controlling Federal agency. The amounts of the 

Wilderness Lands in this study administered by 

the four agencies are as follows: 

Bureau of Land Management: 37 percent, nearly 

27 million acres; 

Forest Service: 45 percent, nearly 34 million 

acres; 

National Park Service: 14 percent, nearly 10 million acres; 

Fish and Wildlife Service: 4 percent, 3 million 

acres. 

Over 20 million acres that may have the 

geologic characteristics necessary for the occurrence of petroleum resources in varying amounts 

(high, medium, and low) are administered by the 

Bureau of Land Management (12.6 million acres) 

and the Forest Service (7. 7 million acres). Theremaining potential 4.5 million acres of the total 25 

million as discussed in table 1 are administered by 

the National Park Service and the Fish and 

Wildlife Service. The Forest· Service has the 

largest amounts of Wilderness Lands with zero 

petroleum potential (16.8 million acres), with the 

Bureau of Land Management second, having 4. 9 

million acres of Wilderness Lands with zero petroleum potential, due primarily to locations within 

terranes with predominantly igneous and (or) 

metamorphic rocks. Mineral resource assessments 

were not included in this study. 

PETROLEUM POTENTIAL MAPS 

The qualitative ratings for petroleum potential 

were numerically encoded, and through application of digital cartographic techniques were used 

to generate machine-plotted, color-coded maps of 

the petroleum potential in the Wilderness tracts in 

each of the 11 States at a scale of 1:1,000,000. 

A complete set of maps, one for each of the 11 

States is being published by the USGS as Miscellaneous Investigations Series Maps (I-1537 

through I-1547, in press; see fig. 1) that shows in 

color the locations and boundaries of the designated and proposed Wilderness Lands in the State 

with official identifications, and the potential for 

petroleum occurrence for each Wilderness tract 

that is dependent upon the known geologic characteristics in the area. In addition, the boundary locations are shown for all other Federal lands and 

Indian lands, along with the geographic, drainage, 

and cultural data, latitude and longitude coordinates, and the locations and identification of the 

USGS petroleum province boundaries. The Iseries maps are published at a scale of 1:1,000,000 

and are being prepared and documented to accompany this report. Additional information on the 

preparation of these maps is discussed by M. A. 

Domaratz and J. A. Stapleton in chapter B in this 

circular on digital cartography. 

TABLE 2.-Petroleum potential by acreage for all Wilderness Lands in the Western United States by controlling Federal agency 

Petroleum potential in thousands of acres 

Federal agency High Medium Low Low-Zero Zero Unknown Total 

Bureau of Land Management 1,039.7 3,562.0 7,954.7 9,401.6 4,926.6 111.6 26,996.2 

Forest Service 1,114.6 1,275.3 5,317.3 7,509.6 16,750.3 1,751.3 33,718.4 

National Park Service 563.4 916.5 1,327.5 2,937.3 2,713.5 1,665.1 10,123.3 

Fish and Wildlife Service 11.5 170.3 1,460.0 1,140.7 308.2 0 3,090.7 

Total 2,729.2 5,924.1 16,059.5 20,989.2 24,698.6 3,528.0 73,928.61 

'Total acreage for all Wilderness Lands is the same as in table 1. All tabulated values are rounded numbers; therefore values may not be precise beyond decimal. 

P3 
MONTANA 

1-1541 

UTAH 

1-1545 

ARIZONA 

1-1537 

WYOMING 

1-1547 

COLORADO 

1-1539 

NEW MEXICO 

1-1543 

FIGURE 1.-Index map of Wilderness Lands study area listing 

identification for USGS Miscellaneous Investigations 

Series Maps I-1537 through I-1547 to be published showing petroleum potential for Wilderness Lands at a scale of 

1:1,000,000. 

RESULTS OF QUANTITATIVE 

PETROLEUM ANALYSIS 

The quantitative petroleum resource analysis 

for the Wilderness clusters for each of the 11 

Western States represents a part of the total estimate of the remaining undiscovered oil and natural gas resources as reported by Dolton and others 

(1981) in Circular 860 for the respective province 

within which the Wilderness Lands occur. Wilderness Lands within the Western States are located 

within 38 of the USGS petroleum provinces defined by Dolton and others (1981) (see appendix). 

The major portions of four of these provinces fall 

outside the eastern limit of the study area. They 

are the Williston basin, Denver basin, Palo Duro 

basin, and the Permian basin. 

The estimates for the individual wilderness clusters are weighted in respect to their geologic characteristics that make them favorable or unfavorable for the occurrence of petroleum. This is calculated by applying the minimum and maximum 

range of richness factors (r) for each cluster. In 

addition, the estimates take into account the marginal probability assigned for recoverable resource 

being present within each wilderness cluster. See 

chapter 0 in this circular by R. A. Crovelli on 

statistical methodology for a detailed explanation 

of the mathematical procedures. 

The quantitative assessments are expressed as 

probability distributions for oil and for natural 

gas. Although it may be convenient to use a point 

estimate, such as the mean as a basis for comparison, a range of values more properly expresses 

the uncertainty inherent in estimates of undiscovered resources. Probability distributions for the 

undiscovered recoverable oil and natural gas for 

the individual wilderness clusters (or tracts) are 

aggregated by a Monte Carlo technique for each of 

the States and for totals for the 11 States. The undiscovered oil and natural gas (unconditional or 

risked assessments) for the individual States are 

presented in figures 2 through 12 and show the 

amounts of resources and the respective probabilities of more than those amounts. Figure 13 

shows the total amounts of undiscovered oil and 

natural gas for all the Wilderness Lands in the 

Western United States. 

The undiscovered recoverable oil for the Wilderness Lands in the 11 Western States is estimated to range from more than 0.555 to 1.490 billion barrels with a mean estimate of 0.834 billion 

barrels. The undiscovered recoverable natural gas 

is estimated to range from more than 5. 536 to 

16.639 trillion cubic feet with a mean estimate of 

9. 729 trillion cubic feet. Each range corresponds 

to the 95 percent and 5 percent probabilities of 

more than the respective amounts. These estimates are reported at the 95 percent and 5 percent probabilities and the mean, median, and 

mode estimates and the standard deviation (S.D.) 

for oil and for natural gas and are summarized in 

table 3 for the separate States and the aggregated 

totals. 

For comparative purposes the total undiscovered recoverable oil and natural gas resources for 

the 38 petroleum provinces, as assessed by Dolton 

and others (1981), were aggregated to provide 

probability distributions for the total resource 

amounts for those provinces in which the Wilderness Lands are located in this study. These distributions are presented in figure 14. An estimated 

percentage range of the amounts of petroleum resources within these 38 provinces which may 

occur within the designated and proposed Wilderness Lands for the 11 Western States is as follows: 

Undiscovered recoverable oil: 2.2 percent to 3.3 

percent of the total oil resource at the 95 and 

5 percent probability range. 

Undiscovered recoverable gas: 3.9 percent to 6.5 

percent of the total natural gas resource at the 

95 and 5 percent probability range. 

P4 
OIL - ARIZONA 

0 

z 

~CD t- 0 

w 

0::: 

~CQ 

Lt... 

0 

0 

~-.: -o 

.J 

([) 

a:"' 

~0 

0::: 

0... 

0 

0 

\ 

~ 

o.o 10.0 --- A 

ESTIMATES 

MEAN - 2.91 

MEDIAN - 0.81 

95% - 0.06 

75% - 0.27 

50% - 0.81 

25% - 2.38 

5% - 11.21 

MODE - 0.06 

S.D. - 10.05 

20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 2A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Arizona. 

OIL - CALifORNIA 

0 

z 

~CD t- 0 

w 

0::: 

~CQ 

Lt... 

0 

0 

~-.: -o 

.J 

([) 

a:"' 

~0 

0::: 

0... 

0 

0 

\ 

\ 

\ 

1\ 

\ 

0.0 9.0 

A 

ESTIMATES 

MEAN - 11.60 

MEDIAN - 8.69 

95% - 2.69 

75% - 5.30 

50% - 8.69 

25% - 11.10 

5% - 30.12 

MODE - 4.94 

S.D. - 10. 18 

~ t---

18.0 27.0 36.0 45.0 54.0 63.0 72.0 81.0 90.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 3A.-Undiscovered recoverable oil resources in Wilderness Lands in 

California. 

GAS - ARIZONA 

0 

z 

~CD t-o 

w 

0::: 

~CQ 

Lt... 

0 

0 

0 

0 

\ 

~ t---

0.0 30.0 

8 

ESTIMATES 

MEAN - 8. 11 

MEDIAN - 2.23 

95% - 0.16 

75% - 0.75 

50% - 2.23 

25% - 6.59 

5% - 31.37 

MODE - 0. 17 

S.D. - 28.41 

60.0 90.0 120.0 150.0 180.0 210.0 240.0 270.0 300.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 2B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Arizona. 

GAS - CALifORNIA 

0 

z 

~CD t- 0 

w 

0::: 

~CQ 

Lt... 

0 

0 

>--.,.. 

t- . -o 

.J 

([) 

a:"' ([) . oo 

0::: 

0... 

0 

0 

\ 

\ 

\ 

\ 

\ 

0.0 4.0 

8 

ESTIMATES 

MEAN - 5.37 

MEDIAN - 4.08 

95% - 1. 37 

75% - 2.55 

50% - 4.08 

25% - 6.64 

5% - 13.64 

MODE - 2.40 

S.D. - 1.54 

~ 1----

8.0 12.0 16.0 20.0 24.0 28.0 32.0 36.0 40.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 3B.-Undiscovered recoverable gas resources in Wilderness Lands in 

California. 
OIL - COLORADO 

0·. 

z 

~CD f-o 

ESTIMATES 

MEAN· - 9.16 

MEDIAN - 5.70 

w 95/. - 3.20 0::: 

~co 0 

75/. - 4.06 

50% - 5.70 

25/. - 9.53 

\ 5% - 25.54 

MODE - 3.42 

\ S.D. - 12.44 

\ 

"'-- "'"-- 0 

ci 

0.0 15.0 30.0 15.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 

A MILLION BARRELS RECOVERABLE OIL 

GAS· COLORADO 

0 

z 

~CD f-o 

w 

0::: 

~co 0 

0 

ci 

\ ESTIMATES 

MEAN - 128.28 

\ MEDIAN - 99.80 

95/. - 31. 11 

75/. - 61.88 

50% - 99.80 1\ 25/. - 160.96 

5/. - 320. 16 

MODE - 60.40 

\ S.D. - 103.60 

0.0 85.0 

8 

~ 1---- 170.0 255.0. 310.0 125.0 510.0 595.0 680.0 765.0 850.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 4A.-Undiscovered recoverable oil resources in Wilderness Lands in Col- FIGURE 4B.-Undiscovered recoverable gas resources in Wilderness Lands in Colorado. orado. 

OIL - IDAHO 

0 

z 

~CD 

'\ 

1\ ESTIMATES 

MEAN - 206.79 f-oo 

w 

0::: 

~co 

MEDIAN - 179.65 

\ 95/. - 77.56 

75/. - 126.73 

SO/. - 179.65 0 

[&_ 

CJ 

>--~ !::o 

_J 

a) 

«:N 

~ci 

0::: 

Q.. 

0 

ci 

0.0 90.0 

A 

\ 25/. - 255.77 

f\ 5/. - 427.38 

MODE - 135.89 

\ S.D. - 116.56 

~ 1---1--

180.0 270.0 360.0 150.0 510.0 630.0 720.0 810.0 900.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 5A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Idaho. 

GAS - IDAHO 

0 

z 

~CD f-o 0 

w 

0::: 

~co 0 

>--~ f-o • -o 

_J 

a) 

«:N 

a) • 

ao 

0::: 

Q.. 

0 

ci 

0.0 

8 

\ ESTIMATES 

MEAN - 1841.25 

\ MEDIAN - 1687.96 

95/. - 850.15 

75/. - 1274. 17 

50/. - 1687.96 

\ 25/. - 2236.14 

5/. - 3351.45 

t\. MODE - 1418.62 

"" 

S.D. - 802.30 

~ ~---~ 

590.0 1180.0 1770.0 2360.0 2950.0 3510.0 1130.0 1720.0 5310.0 5900.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 5B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Idaho. 
OIL - MONTANA 

0 

z 

~CD t- 0 

w 

0:::: 

~(D 

la... 

0 

0 

~ .. ...... o _J 

Q) 

O:N 

~0 

0:::: 

Q.. 

0 

0 

ESTIMATES 

MEAN - 29.55 

MEDIAN - 13.14 

95% - 1. 70 

75% - 5.76 

50% - 13.44 

\ 25% - 31.34 

5% - 105.98 

MODE - 2.78 

\ S.D. - 57.87 

~ 

'----t--

0.0 60.0 120.0 180.0 240.0 300.0 360.0 420.0 480.0 540.0 600.0 

A MILLION BARRELS RECOVERABLE OIL 

FIGURE 6A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Montana. 

OIL - NEVADA 

0 

>-.-

t- • ...... o _J 

Q) 

a:,., 

Q) • 

oo 

0:::: 

Q.. 

0 

0 

ESTIMATES 

MEAN - 92. 11 

MEDIAN - 32.50 

95% - 3.03 

75% - 12.28 

50% - 32.50 

25% - 86.05 

5% - 349.21 \ MODE - 4.05 

\ S.D. - 244.25 

" ..___ 0.0 250.0 

A 

500.0 750.0 1000.0 1250.0 1500.0 1750.0 2000.0 2250.0 2500.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 7A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Nevada. 

GAS - MONTANA 

0 

z 

a: CD ::r. 

t-o 

w 

0:::: 

~~ 0 

......o 

~~ 

_J 

Q) 

O:N 

~0 

0:::: 

Q.. 

0 

0 

\ 

\ 

\ 

1\ 

\ 

0.0 2.3 

8 

ESTIMATES 

MEAN - 3031.33 

MEDIAN - 2240.91 

95% - 623.86 

75% - 1326.54 

50% - 2240.91 

25% - 3785.55 

5% - 8049.33 

MODE - 1224.63 

S.D. - 2761.45 

~ r--- 4.6 6.9 9.2 11.6 13.9 16.2 18.5 20.8 

BILLION CUBIC rEET RECOVERABLE GAS 

FIGURE 6B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Montana. 

GAS - NEVADA 

la... 

0 

0 

...... 

~~ o _J 

Q) 

a:,., 

~0 

0:::: 

Q.. 

0 

0 

\ 

\ 

0.0 

8 

ESTIMATES 

MEAN - 383.35 

MEDIAN - 152.26 

95% - 16.28 

75% - 60.89 

50% - 152.26 

25% - 380.78 

5% - 1423.76 

MODE - 24.02 

S.D. - 885.78 

" ~'--- 900.0 1800.0 2700.0 3600.0 4500.0 5400.0 6300.0 7200.0 8100.0 9000.0 

BILLION CUBIC rEET RECOVERABLE GAS 

FIGURE 7B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Nevada .. 
OIL - NEW MEXICO 

>-.-

f-o • ...... o _] 

aJ 

a:,. 

aJ • ao 

c:r 

Q.. 

0 

d 

\ 

\ 

\ 

\ 

\ 

o.o 8.0 

A 

ESTIMATES 

MEAN - 7.59 

MEDIAN - 5.28 

95% - 2'rl3 

75% - 3.54 

50% - 5.28 

25% - 8.7D 

5% - 20.16 

MODE - 3.04 

S.D. - 7.72 

~ ..____ 

16.0 24.0 32.0 40.0 48.0 56.0 64.0 72.0 . 80.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 8A.-Undiscovered recoverable oil resources in Wilderness Lands in 

New Mexico. 

OIL - OREGON 

0 

>-.-

f-o • ...... o _] 

aJ 

a:,. 

aJ • ao 

c:r 

Q.. 

0 

d 

1 

~ r--

ESTIMATES 

MEAN - 3.42 

MEDIAN - 0.75 

95% - 0.04 

75% - 0.23 

50% - 0.75 

25% - 2.43 

5% - 13. 19 

MODE - 0.04 

S.D. - 15.21 

o.o 15.0 30.0 45.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 

A MILLION BARRELS RECOVERABLE OIL 

FIGURE 9A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Oregon. 

GAS - NEW MEXICO 

0 

~": ......o 

_] 

-m 

~"! ao 

c:r 

Q.. 

0 

d 

\ ESTIMATES 

MEAN - 122.13 

MEDIAN - 97.01 \ 95% - 52.67 

75% - 71.39 

50% - 97.01 

1\ 25% - 142.19 

5% - 273.92 

NODE - 67.00 

\ S.D. - 85.51 

0.0 85.0 

8 

~ 

170.0 255.0 ---340.0 125.0 510.0 595.0 680.0 765.0 850.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 8B.-Undiscovered recovera~le gas resources in Wilderness Lands in 

New Mexico. 

GAS - OREGON 

0 

~": ...... o _] 

m 

a:,. 

~d 

c:r 

Q.. 

0 

d 

ESTIMATES 

MEAN - 69.80 

MEDIAN - 34.84 

95% - 5.01 

75% - 15.73 \ 50% - 34.84 

\ 25% - 77.16 

5% - 242.25 

NODE - 8.68 

\ S.D. - 121.18 

0.0 

8 

"\ 

120.0 

~ 

240.0 - 360.0 480.0 600.0 720.0 840.0 960.0 1080.0 1200.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 9B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Oregon. 
OIL - UTAH 

0 

>-< ... f- • -o 

...J 

m 

m. 

a:,., 

oo 

Q:: 

0.. 

0 

d 

\ ESTIMATES 

MEAN - 120.83 

\ MEDIAN - 69.79 

95% - 12.45 

75% - 34.43 

50% - 69.79 

\ 25% - 141.49 

5% - 391. 14 

MODE - 23.29 

\ S.D. - 170.77 

0.0 

A 

~ t---

165.0 330.0 495.0 660.0 825.0 990.0 1155.0 1320.0 1485.0 1650.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE lOA.-Undiscovered recoverable oil resources in Wilderness Lands in 

Utah. 

OIL - WASHINGTON 

lo... 

0 

0 

t:~ -o 

...J 

m 

CI:N 

~0 Q:: 

0.. 

0 

d 

l 

\ 

"" 0.0 4.0 ---- A 

ESTIMATES 

MEAN - 1.24 

MEDIAN - 0.39 

95% - 0.03 

75% - 0.14 

50% - 0.39 

25% - 1.09 

5% - 4.74 

MODE - 0.04 

S.D. - 3.67 

8.0 12.0 16.0 20.0 24.0 28.0 32.0 36.0 40.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE llA.-Undiscovered recoverable oil resources in Wilderness Lands in 

Washington. 

GAS - UTAH 

0 

:~ z 

~G) 

f- 0 

w 

Q:: i?co 0 

0 

d 

\ 

\ 

\ 

1\ 

~ 1---f--

ESTIMATES 

MEAN - 270.22 

MEDIAN - 169.59 

95% - 34.66 

75% - 88.44 

50% - 169.59 

25% - 325.21 

5% - 829.84 

MODE - 66.80 

S.D. - 335.21 

o.o 

8 

310.0 620.0 930.0 1240.0 1550.0 1860.0 2170.0 2480.0 2790.0 3100.0 

BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE lOB.-Undiscovered recoverable gas resources in Wilderness Lands in 

Utah. 

GAS - WASHINGTON 

lo... 

0 

0 

t:~ -o 

...J 

m 

CI:N 

~d 

Q:: 

0.. 

0 

d 

ESTIMATES 

MEAN - 20.43 

MEDIAN - 9.84 

95% - 1. 35 

75% - 4.35 

SO% - 9.84 

\ 25% - 22.23 

5% - 71.86 

MODE - 2.28 

\ S.D. - 37.18 

" '--......__ 

o.o 40.0 80.0 120.0 160.0 200.0 240.0 280.0 320.0 360.0 400.0 

8 BILLION CUBIC fEET RECOVERABLE GAS 

FIGURE HR.-Undiscovered recoverable gas resources in Wilderness Lands in 

Washington. 
~ 

...... 

0 

OIL - WYOMING 

0 

z 

~CI) 

f-40 

w 

Q:: 

Oco ::1: • 

0 

[a_ 

0 

>-..-

f-4 • ...... o __) 

m 

m. a:N 

oo 

Q:: 

Q.. 

0 

ci 

o.o 

A 

\ ESTIMATES 

MEAN - 348.51 

\ MEDIAN - 296.S8 

95/. - 116.49 

7S% - 202.18 

SO% - 296.S8 

\ 25% - 435.06 

S% - 7S5.08 

MODE - 214.77 

~ S.D • - 215.09 

~ 1---

165.0 330.0 495.0 660.0 82S.O 990.0 1155.0 1320.0 1485.0 1650.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 12A.-Undiscovered recoverable oil resources in Wilderness Lands in 

Wyoming. 

GAS - WYOMING 

0 

z a:CI) 

:I:. 

f-4 0 

w 

Q:: 

~~ 0 

[a_ 

0 

~"': ...... o __) 

m a:N 

~ci Q:: 

Q.. 

0 

ci 

0.0 

8 

......... 

\ ESTIMATES 

MEAN - 3848.69 

\ MEDIAN - 3403.78 

95% - 1506.08 

7S% - 2436.49 

SO% - 3403.78 

1.5 

\ 25/. 

S% 

MODE 

\ S.D. 

" ~ 1'--- 3.0 4.5 6.0 7.6 -- 9.1 10.6 12.1 

BILLION CUBIC fEET RECOVERABLE GAS 

- 4755.10 - 7692.67 - 2662.32 - 2031.09 

13.6 

FIGURE 12B.-Undiscovered recoverable gas resources in Wilderness Lands in 

Wyoming. 
OIL- 11 WESTERN STATES 

z 

g§CD 

f-o 

w 

a::: 

OU» X: • 

0 

>-- ... ...... 

-o 

...J 

m 

m. a:N 

ao 

a::: 

0... 

0 

d 

o.o 

A 

\ ESTIMATES 

ME: AN - 833.72 

\ 

MEDIAN - 716.48 

9S/. - SSS.29 

7S/. - 619.89 

SO% - 716.48 

\ 2S/. - 900.27 

S/. - 1490.39 

MODE - S94.87 

\ S.D. - 390.74 

460.0 920.0 " 1380.0 ---1840.0 2300.0 2760.0 3220.0 3680.0 4140.0 1600.0 

MILLION BARRELS RECOVERABLE OIL 

FIGURE 13A.-Total undiscovered recoverable oil resources in Wilderness Lands 

in 11 Western States. 

~"': -o 

...J 

m a:N 

~d 

a::: 

0... 

0 

d 

OIL 

o.o 15.0 

A 

ESTIMATES 

MEAN - 30.96 

MEDIAN - 28.33 

9S% - 2S.28 

75% - 26.46 

50% - 28.33 

\ 25% - 32.08 

5'% - 44.99 

MODE - 25.88 

S.D. - 8.79 

\ 

~ r--

30.0 45.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 

BILLION BARRELS RECOVERABLE OIL 

GAS - 11 WESTERN STATES 

~~ -o 

...J 

m a:N 

~d 

a::: 

0... 

0 

d 

0.0 3.3 

8 

\ E:STIMATE:S 

ME: AN 

\ MEDIAN 

9S/. 

75/. 

50% 

\ 25/. 

5% 

MODE: 

~ S.D. 

" ~ 6.6 9.9 13.2 16.5 19.7 23.0 26.3 

BILLION CUBIC fEET RECOVERABLE GAS 

- 9728.96 - 8923.69 - SS36.14 - 7193.82 - 8923.69 

-11347.92 

-16638.60 

- 7586.21 - 36S0.55 

29.6 32.9 

M101 

FIGURE 13B.-Total undiscovered recoverable gas resources in Wilderness Lands 

in 11 Western States. 

GAS 

u.. 

0 

~"': -o 

...J 

m a:N 

~c:i 

a::: 

0... 

0 

d 

0.0 55.0 

8 

\ ESTIMATES 

ME: AN - 182.97 

\ MEDIAN - 173.80 

95% - 140.70 

7S% - 1S6.5S 

SO% - 173.80 

!\ 2S% - 198.86 

S'% - 2S6.0S 

MODE - 1S9.20 

\ S.D. - 38.64 

\ 

~~ 110.0 165.0 220.0 275.0 330.0 385.0 410.0 195.0 550.0 

TRILLION CUBIC fEET RECOVERABLE GAS 

FIGURE 14A.-Total undiscovered recoverable oil resources in the 38 USGS west- FIGURE 14B.-Total undiscovered recoverable gas resources in the 38 USGS western petroleum provinces in which Wilderness Lands are located that were in- ern petroleum provinces in which Wilderness Lands are located that were included in this study (Dolton and others, 1981). eluded in this study (Dolton and others, 1981). 
TABLE 3.-Petroleum potential in Wilderness Lands by State in Western United States 

[Acreage expressed in thousands of acres] 

Undiscovered recoverable oiP Undiscovered recoverable gas Total acres 

(million barrels) (billion cubic feet) Total acres of 

assessed Wilderness 

Low2 High Low High with Lands in 

State Fes Fs Mean Fes Fs Mean potential3 State 

Arizona 0.06 11.24 2.91 0.16 31.37 8.11 5,096.0 6,183.8 

California 2.69 30.12 11.60 1.37 13.64 5.37 11,596.0 18,848.6 

Colorado 3.20 25.54 9.16 31.11 320.16 128.28 1,054.4 4,501.1 

Idaho 77.56 427.38 206.79 850.15 3,351.45 1,841.25 2,006.9 7,559.2 

Montana 1.70 105.98 29.55 623.86 8,049.33 3,031.33 5,067.1 6,930.7 

Nevada 3.03 349.21 92.11 16.28 1,423.76 383.35 4,862.7 7,980.6 

New Mexico 2.43 20.16 7.59 52.67 273.92 122.13 1,607.2 2,676.8 

Oregon .04 13.19 3.42 5.01 242.25 69.80 4,865.8 4,865.8 

Utah 12.45 391.14 120.83 34.66 829.84 270.22 3,857.6 4,482.8 

Washington .03 4.74 1.24 1.35 71.86 20.43 3,892.9 3,892.9 

Wyoming 116.49 755.08 348.51 1,506.08 7,692.67 3,848.69 1,795.9 6,007.0 

Total 555.29 1,490.39 833.71 5,536.14 16,638.60 9,728.96 45,701.5 73,928.3 

'The marginal probabilities of a resource for the wilderness clusters were applied to the corresponding conditional probability distribution of the quantity of undiscovered 

recoverable resource. These distributions, used in this report, are referred to as the "unconditional" or "risked" distribution. 

•F .. denotes the 95th fractile; the probability of more than the amount F .. is 95 percent. F • is defined similarly. Fractile values are not additive. 

"The total"acres of Wilderness Lands assessed with potential for each of the States include those lands assigned a high, medium, low, and low to zero potential. The Wilderness Lands not included in the quantitative assessment procedures are those assigned a zero potential or an unknown potential. 

The percentage estimates of the amounts of petroleum resources within the Wilderness Lands of 

the 11 Western States relative to the total provinces is a conservative estimate. This is due to 

the fact that major portions of four of the petroleum provinces extend beyond the eastern boundary of the 11-State study area and three of the 

four are major petroleum producing provinces: the 

Williston Basin, the Denver Basin, and the Permian Basin. A more accurate calculation of the 

percent of the resources in the Wilderness Lands 

of the 11 Western States relative to the total resources of these States would require the subtraction from the total of those resources in the four 

provinces which extend eastward beyond the 

study area boundaries and outside the 11-State 

area. 

To put these comparative estimates into perspective, it is essential to consider the distribution 

of the sizes of the wilderness tracts within the 

Western States relative to the distribution of the 

Wilderness Lands which fall within prospectively 

favorable sedimentary provinces versus those Wilderness Lands that occur within unfavorable igneous and metamorphic terranes, or those Wilderness Lands which fall within geologic terranes 

that are either considered to have zero potential 

or are unknown in their petroleum potential. 

Table 4 summarizes some of these statistical relationships relative to the distribution and size of 

the wilderness tracts. 

The minimum- to the maximum-sized wilderness 

tract ranges from 4 acres in California to 2. 5 million acres in Idaho. The average tract size for the 

1, 636 digitized wilderness polygons is 45 thousand 

ac~es or approximately 70 square miles. These relationships are pertinent to the issue of speculating on the probable field size distributions that 

may occur within any of the wilderness tracts. At 

the present time there is not sufficient geologic 

data on any of the petroleum prospective wilderness tracts to make credible estimates of the field 

sizes likely to occur within these lands. It is important to note, however, that the bulk of petroleum resources in most sedimentary basins is 

likely to be concentrated in a relatively few larger 

fields. It is conceivable that a number of the prospective wilderness tracts could support the occurrence of some significant oil and gas fields. It 

is also highly unlikely that oil and gas fields of any 

significant size would occur in some of the very 

small wilderness tracts. The two smallest wilderness tracts recorded were in California at 4 and 9 

acres respectively. The largest wilderness tract 

recorded was in Idaho at 2.5 million acres, or 

3,906 square miles with zero petroleum potential 

due to location over the Idaho batholith. 

P12 
TABLE 4.-Statistics on the distribution of Wilderness Lands in the Western United States 

[Acreage expressed in thousands of acres) 

Total acreage 

Total acreage with low to Total acres 

Number of Minimum- Maximum- with zero and with zero Total acreage 

wilderness sized tract sized tract Average petroleum unknown petroleum Wilderness 

State polygons1 recorded recorded tract size potential potential potential Lands 

Arizona 164 0.185 517.6 37.7 1,567.2 3,528.8 1,087.8 6,183.8 

California 511 .004 699.3 36.9 1,346.7 10,249.3 7,252.6 18,848.6 

Colorado 122 .183 170.0 36.9 1,054.4 1,001.4 2,445.3 4,501.1 

Idaho 94 .178 2,465.8 80.4 983.2 1,060.4 5,515.6 7,559.2 

Montana 150 .072 1,543.6 46.2 3,854.9 1,250.4 1,825.4 6,930.7 

Nevada 136 .540 416.9 58.7 4,862.7 0 3,117.9 7,980.6 

New Mexico 82 .233 545.1 32.6 1,449.2 158.0 1,069.6 2,676.8 

Oregon 114 .120 513.8 42.7 3,007.9 1,857.9 0 4,865.8 

Utah 129 .189 477.8 34.8 3,857.6 0 625.2 4,482.8 

Washington 42 2.393 843.9 92.7 •952.4 2,940.5 0 3,892.9 

Wyoming 92 .150 664.2 65.3 1,776.9 2,470.8 1,759.3 6,007.0 

Total 1,636 .004 2,465.8 45.2 24,713.1 24,517.5 24,698.7 73,928.32 

'The number of wilderness polygons is the number of individual closed plane figures (or tracts) which were digitized from the land status maps and calculated for acreage. 

This number is equal to or greater than the actual number of legally identified wilderness tracts. Many of the Wilderness Lands were digitized in separate pieces when the 

wilderness area was broken up by streams and other mapped discontinuities. 

'All tabulated values for total acreage are rounded numbers; therefore, values may not be precise beyond decimal. 

Additional geologic and geophysical data that 

may be available in the future and (or) any significant oil or gas field discoveries relative to the location of the Wilderness Lands would require a 

reevalaution of the oil and gas resource estimates 

to stay current with the state of geologic knowledge in these areas. 

SUMMARY 

In 1982-83, the U.S. Geological Survey (USGS) 

conducted an investigation of the oil and gas potential of the designated and proposed Wilderness 

Lands in the Western United States. This undertaking was in response to the national concerns in 

the last few years over sources for continuing energy supplies which centered around the issue of 

the probable occurrence of energy and nonenergy 

minerals on Federal lands. In particular, the most 

controversial issues have been focused upon the 

potential of the Nation's Wilderness Lands. 

In this ongoing effort to access the petroleum 

potential on all Federal lands, the scope of this 

study is limited to the conventional recoverable 

petroleum resources occurring in the designated 

and proposed Wilderness Lands of the Western 

United States. This includes the Wilderness 

Lands administered under four Federal agencies: 

Bureau of Land Management (BLM), U.S. Forest 

Service (USFS), National Park Service (NPS), 

and Fish and Wildlife Service (FWS). 

The total area of the study includes approximately 7 4 million acres of Wilderness Lands in 

these 11 Western States: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, 

Oregon, Utah, Washington, and Wyoming. The 74 

million acres represent 31 percent of the total 

Federal lands within these 11 Western States. 

Approximately 49 percent of all the lands in these 

States are federally owned. 

The objective of this study is to assemble 

through various means all the available pertinent 

information that can be brought together within 

the USGS and integrate these data into a computer-based digital cartographic data system that 

is focused upon the single issue of reviewing the 

known geological and geophysical data to determine the geologic characteristics favorable or unfavorable for the occurrence of petroleum resources in these Wilderness Lands. In a joint effort in the USGS between the Geologic Division 

(GD) and the National Mapping Division (NMD) 

all of the mappable information used in this study 

was prepared and processed by using digital cartographic techniques. These include digitizing the 

location and boundaries of the Wilderness Lands; 

acreage calculations; the boundaries of the USGS 

petroleum provinces; and the geologic and tectonic 

P13 
boundaries within each petroleum province and 

State. In addition, searches were conducted on 

well data files which provided the locations and 

geologic information on over 5,000 wells drilled 

within or immediately adjacent to the Wilderness 

Lands. 

An analysis of all the geologic characteristics 

favorable or unfavorable for petroleum occurrence 

in conjunction with the geologic settings for the 

Wilderness Lands scattered within the framework 

of the petroleum provinces was performed by a 

team of geologists on each of the wilderness 

tracts. The geologic characteristics reviewed for 

each tract included the presence or absence of the 

following: adequate source beds and reservoir 

rocks; adequate trapping mechanisms; favorable 

thermal and maturation histories; presence of petroleum seeps or adjacent wells with shows or 

production; and the presence of favorable 

sedimentary rock sections underlying volcanic terrane or faulted and overthrust areas. 

A description of the geology and geologic 

framework is provided for each State along with 

an explanation of the interpretative geology and 

evaluation of the petroleum potential within the 

locaie of each of the wilderness tracts. 

The assessment of the petroleum resources on 

the Wilderness Lands was completed in two separate stages. In the first stage the geologists 

evaluated the geological characteristics for the 

favorability or lack of favorability for the occurrence of oil and natural gas within each wilderness 

tract and assigned a qualitative rating for each 

tract's potential for the occurrence of recoverable 

oil and gas resources. In the second stage in 

evaluating the petroleum potential for the wilderness tracts, an effort was made to arrive at a 

quantitative assessment within the framework of 

the USGS's latest published resource estimates 

which are made on a province basis (Dolton and 

others, 1981). The geologic characteristics 

evaluated for the favorability of petroleum occurrence within each of the clusters of wilderness 

tracts were the determining factors for the subjective assessments of the petroleum potential for 

each wilderness tract occurring within the respective basin or province. The quantitative resource 

assessments are subjectively determined as to the 

richness and potential of the wilderness tracts relative to the total petroleum potential for the respective petroleum province within which they 

occur. 

The results of the qualitative analysis of the petroleum potential of the Wilderness Lands are 

tabulated by total acreages for each wilderness 

tract as classified by its potential rating. These 

tabulations are made for the Wilderness Lands by 

_petroleum province, by State, and for the total 

Wilderness Lands in the 11 Western States. A 

summary is provided of the petroleum potential 

by acreage for all the Wilderness Lands in the 

Western United States by State and for the total 

11 States. At least 34 percent of the total acreage 

for Wilderness Lands, or approximately 25 million 

acres, may have the geologic characteristics necessary for the occurrence of petroleum resources 

in varying amounts (high, medium, and low potential). An additional 33 percent of the Wilderness 

Lands may have some limited potential where 

small sedimentary areas are mixed within igneous 

and metamorphic terrane, but are more likely to 

fall in the low to zero potential. Finally, 33 percent of the Wilderness Lands probably have no 

petroleum potential because they are located in 

terranes with predominantly igneous and (or) 

metamorphic rocks in which petroleum has rarely 

been found. 

The quantitative petroleum assessments for the 

Wilderness Lands in the Western United States 

represent a part of the total estimate of the remaining undiscovered oil and natural gas for the 

38 petroleum provinces within which the Wilderness Lands occur, as defined by Dolton and others 

in USGS Circular 860 in 1981. The undiscovered 

recoverable oil for the Wilderness Lands in the 

Western States is estimated to range from more 

than 0.555 to 1.490 billion barrels with a mean estimate of 0.834 billion barrels. The undiscovered 

recoverable natural gas is estimated to range from 

more than 5.536 to 16.639 trillion cubic feet with 

a mean estimate of 9. 729 trillion cubic feet. Each 

range corresponds to the 95 and 5 percent probabilities of more than the respective amounts. The 

oil and gas resource estimates reported at the 95 

percent and 5 percent probabilities and the mean 

estimates are summarized for the separate States 

and the aggregated totals. 

For comparative purposes the total undiscovered recoverable oil and gas resources estimated 

for the 38 petroleum provinces in the Western 

United States were aggregated from Dolton and 

others (1981) to provide probability distributions 

for the total oil and gas resource amounts for 

those western provinces in which the 74 million 

P14 
··~····:. 

acres of Wilderness Lands are located in this 

study. An estimated percentage range of the 

amounts of undiscovered recoverable petroleum 

resources within these 38 petroleum provinces 

which may occur within the. designated and proposed Wilderness Lands for the Western States 

are more than 2.2 percent to 3.3 percent of the 

total oil resource, and more than 3.9 percent to 

6.5 percent of the total natural gas resource, reported at the 95 percent and 5 percent probability 

range. 

A series of printed maps, one for each Western 

State, accompanies this report (USGS Miscellaneous 

Investigations Series Maps I-1537-I-1547, in 

press) and show in color the location and qualitative petroleum potential of the Wilderness Lands 

studied, with BLM identification of wilderness 

tracts; the boundary locations of all major Federal 

and Indian lands; the boundaries and identification 

of the USGS petroleum provinces; and other base 

P15 

information. A pamphlet accompanies each State 

map describing the geology of the State and the 

local geology relative to the position of the wilderness tracts and their petroleum potential. These 

maps were compiled by using traditional cartographic techniques from digitally produced graphics 

and are published as separate sheets for each 

State at a scale of 1:1,000,000. 

REFERENCE CITED 

Dolton, G. L., Carlson, K. H., Charpentier, R. R., Coury, A. 

B., Crovelli, R.A., Frezon, S. E., Khan, A. S., Lister, J. 

H., McMullin, R. H., Pike, R. S., Powers, R. B., Scott, 

E. W., and Varnes, K. L., 1981, Estimates of undiscovered recoverable conventional resources of oil and gas in 

the United States: U.S. Geological Survey Circular 860, 87 

p. 
CONCLUSIONS 

By Betty M. Miller 

The purpose of this study was twofold: (1) to assemble through various means all the available 

pertinent information within the USGS which focused upon the single issue of reviewing the 

geological and geophysical data to determine the 

geologic characteristics favorable or unfavorable 

for the occurrence of petroleum resources in 74 

million acres of Wilderness Lands in the Western 

United States and (2) to estimate the potential petroleum resources that may occur within these 

Wilderness Lands both by qualitative assessment 

rating procedures and by estimating the quantities of conventional recoverable oil and natural 

gas that may occur within these lands by using 

subjective probability procedures. 

The complexity of multiple data sources which 

are essential to the assessment of petroleum potential in the Wilderness Lands scattered across 

the vast expanse of the Western United States 

can be rapidly compiled, relatively speaking, and 

integrated into a multivariate data system by applying digital cartographic techniques. By applying these digital techniques, the lead-time for data 

compilation and assimilation for such a large undertaking can be significantly reduced which allows the geologists to proceed more rapidly to the 

analysis, evaluation, and assessment stages of the 

project. The integration of the basic data by computerized systems and digital cartographic technology also provides a vehicle in which the intermediate results derived during the study can be 

incorporated into the computerized system, tabulated, and summarized for the final results. Thus 

the digital cartographic data are easily updated, 

rapidly processed, and provide a rapid and flexible 

means of preparing final data tabulations and 

machine-produced map products. 

The USGS Miscellaneous Investigations Series 

Maps showing the petroleum potential for the Wilderness Lands in the 11 Western States, a product of 

the qualitative analysis, provide a unique and useful set of maps at a scale of 1:1,000,000 (I-1537-

I-1547, in press). The locations and identification 

of the administrating agencies of the designated 

and proposed Wilderness Lands shown on the 

State maps along with their respective potential 

for the occurrence of petroleum resources and the 

boundaries of the petroleum provinces provide a 

perspective for the users of these maps relative to 

the probable resource potential of these Federal 

lands. 

Those lands with reported high, medium, and 

low petroleum potential usually occur in areas possessing sedimentary geological characteristics, 

whereas those with low to zero and zero potential 

range from mixed sedimentary to metamorphic 

and igneous or volcanic terranes. However, areas 

of low to zero petroleum potential may be highly 

favorable for mineral potential, or in some instances areas in which other unconventional organic resources such as oil shales, tight gas sands, 

and coal deposits occur. Energy and mineral commodities other than conventional recoverable oil 

and natural gas were not included in this study. 

At least 34 percent of the total acreage in Wilderness Lands, approximately 25 million acres, may 

have the geologic characteristics necessary for the 

occurrence of petroleum resources in varying 

amounts of high, medium, and low potential. An 

additional 33 percent of the Wilderness Lands 

may have some limited potential, but is more 

likely to fall in the low to zero potential and in the 

unknown categories. Finally, 33 percent of the 

Wilderness Lands probably have no potential petroleum because they are located in terranes with 

predominantly igneous and (or) metamorphic 

rocks in which petroleum has rarely been found. 

The quantitative assessments of the petroleum 

potential in Wilderness Lands are based upon the 

results of procedures which the geologists have 

sequentially followed from the input in the qualitative assessments to the subjective estimates 
which provide the output as probability distributions reported for the quantitative estimates. The 

quantitative resource assessments are subjectively determined as to the richness and potential 

of the wilderness tracts relative to the total petroleum potential for the respective petroleum province within which they occur. These risked estimates are reported as probability distributions 

with minimum and maximum estimated amounts 

of conventional undiscovered recoverable oil and 

gas resources reported at the 95 percent and 5 

percent probability levels. 

The undiscovered recoverable oil for the total 

Wilderness Lands in the Western States based 

upon currently available information is estimated 

to range from more than 0.555 to 1.490 billion barrels with a mean estimate of 0.834 billion barrels. 

The undiscovered recoverable natural gas is estimated to range from more than 5.536 to 16.639 

trillion cubic feet with a mean estimate of 9. 729 

trillion cubic feet. These assessments should be 

viewed in light of the currently available and often 

limited geologic information which is frequently 

interpreted with a high degree of uncertainty 

where subsurface information is unavailable due 

to no exploratory drilling within many of the 

areas. 

Additional geologic and geophysical data that 

may be available in the future and (or) any significant oil or gas field discoveries relative to the location of the Wilderness Lands would require a 

reevaluation of the oil and gas resource estimates 

to stay current with the state of geologic knowledge in these areas. 
APPENDIX 

RESOURCE APPRAISAL GROUP (RAG) 

PETROLEUM PROVINCES BY NUMBER, NAME, 

AND STATES IN WHICH WILDERNESS LANDS 

OCCUR FOR WESTERN UNITED STATES1 

Pacific Coast 

Regions and provinces 

Number and name 

72 Western Oregon-Washington 

73 Sacramento Basin 

7 4 San Joaquin Basin 

75 Los Angeles Basin 

76 Ventura Basin 

77 Santa Maria Basin 

78 Central Coastal Basins 

79 Sonoma-Livermore Basins 

80 Humboldt Basin 

81 Eastern Oregon-Washington 

81A Eastern California 

Colorado Plateau and Basin and Range 

82 Eastern Basin and Range 

83 Western Basin and Range 

84 Idaho-Snake River Downwarp 

85 Paradox Basin 

86 Uinta-Piceance-Eagle Basins 

87 Park Basins 

88 San Juan Basin 

89 Albuquerque-Santa Fe-San Luis Rift Basins 

90 Wyoming-Utah-Idaho Overthrust Belt 

91 Northern Arizona 

92 South-central New Mexico 

93 Southern Arizona-Southwestern New Mexico 

Rocky Mountains and Northern Great Plains 

94 Williston Basin 

96 Sweetgrass Arch 

97 Central Montana 

98 Montana Overthrust Belt 

99 Southwestern Montana 

100 Wind River Basin 

101 Powder River Basin 

102 Southwestern Wyoming Basins 

103 Big Horn Basin 

104 Denver Basin 

105 Las Animas Arch 

106 Raton Basin-Sierra Grande Uplift 

West Texas and Eastern New Mexico 

107 Permian Basin 

108 Palo Duro Basin 

109 Pedernal Uplift 

States in which 

Wilderness Lands occur 

Oregon and Washington 

California 

California 

California 

California 

California 

California 

California 

California 

Oregon and Washington 

California 

Utah, Nevada, and Idaho 

Nevada 

Idaho 

Utah and Colorado 

Utah and Colorado 

Colorado 

New Mexico and Colorado 

New Mexico and Colorado 

Wyoming, Utah, and Idaho 

Arizona 

New Mexico 

Arizona and New Mexico 

Montana1 

Montana 

Montana 

Montana and Idaho 

Montana 

Wyoming 

Montana and Wyoming 

Wyoming, Utah, Colorado, and Idaho 

Wyoming and Montana 

Colorado and Wyoming1 

Colorado1 

Colorado and New Mexico 

New Mexico1 

New Mexico1 

New Mexico1 

•States not included are outside of study area. (Taken from Dolton and others, 1981.)