Abstract: United States and Utah Oil-Impregnated Rock (Tar Sand) Resources

Howard R. Ritzma

Oil-impregnated rock is reported on every continent except Australia and Antarctica. In North America, the deposits of northeast Alberta, Canada, contain hundreds of billions of barrels of oil, possibly as much as a trillion. In South America, the "Tar Belt" of Venezuela contains oil also measurable in amounts up to a trillion barrels. In the United States oil-impregnated rock is reported in 24 states. Ten states have significant resources, and Utah has 90 to 95% of the mapped resource.

Fifty-one deposits are present in Utah. These range from giants extending beneath hundreds of square miles to tiny patches less than an acre (0.25 ha.) in extent. Twenty-five deposits are grouped in and around the Uinta basin of northeast Utah; 22 are in central-southeast Utah; and four minor deposits are scattered elsewhere in the state.

In the Uinta basin almost all oil contained in oil-impregnated rock appears to have originated in highly organic, lake sediments of early Tertiary age (Paleocene and Eocene), and in the Wasatch and Green River Formations (the latter formation also contains the giant oil-shale resources of Utah and Colorado). The oil is paraffinic with a sulfur content about 0.4%.

In central southeast Utah deposits are mainly in formations of Permian and Triassic age. Oil originated in shallow-marine lagoonal or shoreline environments. It has a sulfur content ranging from 3.0% to 4.5%.

Present activity is confined to the Asphalt Ridge deposit where Sohio Petroleum has opened a surface mine which is also the site of a pilot extraction plant operated by Aminoil. On the Northwest Asphalt Ridge deposit ERDA (formerly U.S. Bur. Mines) has conducted a reverse-combustion fireflood experiment in recent years. A proposed in-situ experiment in central southeast Utah is stalled by legal and environmental problems.

Development of the resource in Utah has been slowed by lease and legal complications and environmental entanglements. Competition for water supply with oil shale and coal is also a limiting factor in potential development. Economic factors also are unfavorable at present.

Conservatively estimates show that Utah's deposits contain 25.13 billion bbl of oil in place, but the total may be half again as much.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC