Abstract

Oil and gas resources on University Lands, 2.1 million acres in 19 West Texas counties, and the production from these resources constitute a major asset of The University of Texas System. The original oil in place (OOIP) of the 102 major University Lands oil reservoirs is calculated to be 7,520 million bbl as of yearend 1999. Components of the calculated OOIP include residual oil (3,761 million bbl, 49 percent), cumulative production (1,702 million bbl, 23 percent), remaining reserves (125 million bbl, 2 percent), and unrecovered mobile oil (1,932 million bbl, 26 percent). Ultimate recovery of the 49 major University Lands gas reservoirs is calculated as 2.4 Tcf as of yearend 1999. The gas resource base has been divided into cumulative production since 1987 (1.5 Tcf, 62 percent) and remaining reserves (0.9 Tcf, 38 percent).

The major oil and gas reservoirs on University Lands have been delineated into 22 plays. Historically the Silurian-Devonian and San Andres-Grayburg plays have been the major oil plays on University Lands. However, the greatest future potential in terms of unrecovered mobile oil exists in the Clear Fork carbonate and Spraberry-Dean submarine fan sandstone plays. Historical gas production and remaining reserves by play are dominated by the Thirtyone deep water chert play. This play has dwarfed all other gas plays on University Lands.

Although most of the major oil and gas reservoirs on University Lands are mature, significant opportunities for incremental recovery exist in terms of unrecovered mobile oil—the volume that is the future target of reserve growth opportunities. Previous advanced reservoir characterization and recovery studies for 16 University Lands oil fields conducted by the Bureau of Economic Geology have played a pivotal role in providing a better understanding of production mechanisms and geology as well as enabling incremental production. The current updated resource assessment provides a tool in targeting major fields that have similar opportunities for incremental production.