U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3133

November 2006

National Assessment of Oil and Gas Fact Sheet

Natural Bitumen Resources of the United States

Printed on recycled paper

Introduction

Natural bitumen accumulations in the United States are generally known as “tar sands,” a generic term that has been used for 

several decades to describe petroleum-bearing rocks exposed on the 

Earth’s surface (fig. 1). Other terms for such accumulations include 

oil sand, oil-impregnated sand, asphaltic sand, rock asphalt, bituminous rock, and bitumen-bearing rock. Natural bitumen is defined as 

petroleum with a gas-free viscosity greater than 10,000 centipoises 

(cp) at original reservoir temperature (fig. 2). Petroleum with a gasfree viscosity between 10,000 and 100 cp is generally termed heavy 

crude oil. In the absence of viscosity data, oil with API gravity less 

than 10 degrees is generally considered a natural bitumen (Danyluk 

and others, 1984), whereas oil with API gravity ranging from 

10 degrees API to about 20 degrees API is considered heavy crude 

oil. The term “extra-heavy crude oil” is used for oil with a viscosity 

less than 10,000 cp but with API gravity less than 10 degrees.

The locations of more than 500 accumulations of natural 

bitumen in the United States were compiled by Ball Associates 

Ltd. (1965), but resource estimates were provided for only a limited 

number of the accumulations. The most recent study providing 

Major natural bitumen accumulations in the 

United States are estimated to contain about 36 billion

barrels of measured in-place resource and about 

18 billion barrels of speculative in-place resource. 

Major natural bitumen resources are in Alabama, 

Alaska, California, Kentucky, New Mexico, Oklahoma, 

Texas, Utah, and Wyoming.

Figure 1. Photograph of an outcrop of cross-stratified fluvial sandstone 

with natural bitumen (black), Sunnyside accumulation, Carbon County, Utah. 

Hammer for scale.

Figure 2. Definition of natural bitumen and heavy oil based on viscosity, 

density, and API gravity (modified from Danyluk and others, 1984). mPa-s, 

millipascal-second; kg/m3, kilogram per cubic meter; cp, centipoises; °API, 

degrees API; °C, degrees Celsius; °F, degrees Fahrenheit.

estimates of both measured and speculative in-place resources for 

the Nation’s major natural bitumen accumulations (those containing more than 100 million barrels of oil [MMBO] in-place) was by 

Lewin and Associates, Inc. (1984). The estimates given in table 1 

are from Lewin and Associates, Inc. (1984) for the conterminous 

United States and from Kamath and others (1995) for northern 

Alaska. These estimates represent in-place resources but do not 

represent either technically recoverable resources or economically 

recoverable resources. Recovery factors to determine technically 

or economically recoverable resources are difficult to predict, 

given that recovery procedures might range from surface mining to 

subsurface technology such as that involving steam-assisted gravity 

drainage from paired well bores. Measured resources are generally 

those estimated from areal dimensions and bitumen saturations of 

deposits at the surface. Speculative resources, on the other hand, 

are generally those representing the subsurface extension of a surface accumulation, so considerable uncertainty exists in estimating 

their volumes. For example, estimates of the speculative in-place 

bitumen resource for the Tar Sand Triangle accumulation in Wayne 

and Garfield Counties, Utah, range from 420 million barrels of 

bitumen (Lewin and Associates, Inc., 1984) to 16 billion barrels of 

bitumen (Campbell and Ritzma, 1979).

Gas-free viscosity at original reservoir temperature

(Density at 15.6°C (60°F) at atmospheric pressure)

Viscosity : mPa.s (cp)........ 100

Density : (kg/m3).......... (934)

API Gravity : (°API).......... (20) (10)

10,000

(1,000)

LIGHT

CRUDE

OIL

HEAVY

CRUDE

OIL

NATURAL

BITUMEN

Tar-Sand Resource Summary

For 29 major tar-sand accumulations in the United States, 

the total measured in-place resource is estimated to be about 

36,000 MMBO, and the total speculative in-place resource is 

estimated to be about 18,000 MMBO (table 1). Major natural 

bitumen resources are in Alabama, Alaska, California, Kentucky, 

New Mexico, Oklahoma, Texas, Utah, and Wyoming (table 1). 

Utah is estimated to contain about 18,680 MMBO in 10 major 

accumulations. If the higher published numbers for the speculative 

resource in the Tar Sand Triangle deposit are used (Campbell and 

Ritzma, 1979), the total in-place resource for Utah could possibly 

include another 16,000 MMBO. The Ugnu Sand accumulation 

on the North Slope of Alaska is estimated to contain a measured 
Table 1. Summary of estimates of measured in-place and speculative in-place natural bitumen resources for the major accumulations in the 

United States.

[MMBO, million barrels of oil; NA, reservoir temperature not available; cp, centipoises; °API, degrees API; >, greater than; °F, degrees Fahrenheit]

Deposit name State

Viscosity

(cp @ reservoir

temperature [°F])

API

gravity

range

(°API)

API

gravity

average

(°API)

Measured

in-place

resources

(MMBO)

Speculative

in-place

resources

(MMBO)

Total

in-place

resources

(MMBO)

Hartselle Alabama 1,760 4,500 6,260

Pride Mountain Alabama 100 100

Ugnu Sands Alaska 60,000–10,000,000@NA 7.1–11.5 10 15,000 15,000

Arroyo Grande California 15,000@100°F 8 310 310

Basal Foxen California 47,000@80°F 9.0–17.0 9.5 1,900 1,900

Cat Canyon California 12,000–1,000,000@NA 0.0–12.0 6 830 280 1,110

Casmalia Diatomite California 90 170 260

Zaca-Sisquoc California 4.0–6.0 180 50 230

Oxnard California 500,000@100°F 5.0–8.0 5 500 160 660

Big Clifty Kentucky 15,000–150,000@NA 10 1,190 910 2,100

Hardinsburg Kentucky 10 230 190 420

Tar Springs Kentucky 340 340

Caseyville Kentucky 300 250 550

Santa Rosa New Mexico 30,000@60°F 12 130 220 350

S. Central Oklahoma Oklahoma 4 800 800

San Miguel Texas 20,000–20,000,000@95°F –0.5– –2 –2 3,200 610 3,810

Anacacho Texas 235,000@70°F 550 400 950

Hensel Texas 7 120 120

Circle Cliffs Utah –11.1–6.8 –2.9 560 1,140 1,700

Tar Sand Triangle Utah 100,000@NA –3.6–9.6 4.3 2,500 420 2,920

Nequoia Arch Utah 730 160 890

San Rafael Swell Utah 300 250 550

P.R. Spring Utah 1,000,000@77°F 5.8–15.3 9.5 2,100 2,200 4,300

Hill Creek Utah 5.5–17.3 9.1 300 600 900

Sunnyside Utah 100,000@NA 7.6–9.2 8.6 4,400 1,700 6,100

Whiterocks Utah 100,000@NA 4.0–12.0 60 60 120

Asphalt Ridge Utah >1,000,000@NA 8.2–12.9 10.4 800 300 1,100

Raven Ridge Utah 1,000,000@NA 4.4–9.9 7.4 100 100

Burnt Hollow Wyoming 1,000,000@53°F 5.0–9.0 120 25 145

TOTALS 36,360 17,735 54,095

in-place resource of about 15,000 MMBO (Kamath and others, 

1995) and is gradational with the heavy oil accumulation in the 

giant Kuparuk oil field. Estimates of in-place natural bitumen 

resources in other States are: (1) Alabama, two accumulations with 

about 6,360 MMBO in-place resource; (2) Texas, three accumulations with about 4,880 MMBO; (3) California, six accumulations 

with about 4,470 MMBO; (4) Kentucky, four accumulations with 

about 3,410 MMBO; (5) Oklahoma, one accumulation with about 

800 MMBO; (6) New Mexico, one accumulation with about 

350 MMBO; and (7) Wyoming, one accumulation with about 

145 MMBO.

For Additional Information

Additional information for U.S. onshore oil and gas resources 

are available on the U.S. Geological Survey Energy Program Web 

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

Natural Bitumen Characterization Team

Christopher J. Schenk (schenk@usgs.gov), Richard M. 

Pollastro, and Ronald J. Hill

References

Ball Associates Ltd., 1965, Surface and shallow oilimpregnated rocks and shallow oil fields in the United 

States: U.S. Bureau of Mines Monograph no. 12, 375 p.

Campbell, J.A., and Ritzma, H.R., 1979, Geology and petroleum 

resources of the major oil-impregnated sandstone deposits 

of Utah: Utah Geological and Mineralogical Survey Special 

Studies no. 50, 24 p.

Danyluk, M., Galbraith, B., and Omana, R., 1984, Towards definitions for heavy crude oil and tar sands, in Meyer, R.F., 

Wynn, J.C., and Olson, J.C., eds., The future of heavy 

crude and tar sands: United Nations Institute for Training 

and Research (UNITAR) Second International Conference, 

Caracas, Venezuela, February 7–17, 1982, p. 7–11.

Kamath, V.A., Sharma, G.D., Ogbe, D.O., Patil, S.L., and Khataniar, S., 1995, Assessment of resource and recovery potential of Ugnu tar sands, North Slope, Alaska, in Meyer, R.F., 

ed., Heavy crude and tar sands—Fueling for a clean and safe 

environment: Sixth United Nations Institute for Training and 

Research (UNITAR) Conference on Heavy Crude and Tar 

Sands, Houston, Texas, February 12–17, 1995, p. 141–157.

Lewin and Associates, Inc., 1984, Major tar sand and heavy oil 

deposits of the United States: Interstate Oil Compact Commission, Oklahoma City, Oklahoma, 272 p.