Abstract: Geologic Appraisal of Undiscovered Oil and Gas Resources in Permian Rocks of Permian Basin, West Texas and Southeastern New Mexico

Anny B. Coury, Katharine L. Varnes, Russell W. Allen

The Permian basin of West Texas and southeastern New Mexico has been this country's second most prolific petroleum region, and more than two-thirds of the hydrocarbons in the basin have been found in the Permian System. A new study for the Interagency Oil and Gas Supply Project indicates that only moderate to small amounts of oil and gas remain to be discovered in rocks of Permian age within the basin.

In the study area, which covers 85,000 sq mi (220,000 sq km), the Permian System has an average thickness of 7,500 ft (2,300 m), and a volume of about 110,000 cu mi (458,000 cu km); the maximum thickness of Permian rocks exceeds 17,000 ft (5,200 m). Major structural elements include the Eastern shelf, Midland basin, Central basin platform, Delaware and Val Verde basins, and Northwest shelf.

The discovered resources in the Permian System are 65 billion bbl of oil in place (average recovery factor 25%), 9 Tcf of associated/nonassociated gas in place, and 32 Tcf of dissolved gas in place.

Field-size distributions, finding rates, and original oil in place are presented by both series and depth intervals. Drilling density maps define extensively explored, inadequately explored, and undrilled areas.

Hydrocarbon-yield factors are derived by series, producing trend, depth interval, and drilling density. These yield factors are projected into inadequately drilled and unexplored areas where geology and lithology define volumes of potential reservoirs.

The results of these resource appraisals are reported as probability and frequency distributions as part of a comprehensive reappraisal of Paleozoic rocks in the basin by the U.S. Geological Survey.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma