San Andres and Grayburg reservoirs have yielded about 42 percent (9.8 billion barrels) of the total cumulative production of oil from the Permian Basin of West Texas.

The East Penwell San Andres Unit produces from a depth of approximately 3,400 ft (1,040 m) on the east flank of a broad, low-relief anticline on the east side of the Central Basin Platform of the Permian Basin in Ector and Crane Counties, West Texas.

Unrecovered mobile oil is oil that is movable at reservoir conditions but is prevented from migrating to existing we1 l bores because of geologic complexities or heterogeneities.

A waterflood was begun in 1985 in Taylor-Link West San Andres unit (10 million barrels cumulative production) on the south margin of the Central Basin Platform to capture a remaining mobile oil target estimated at 20 million barrels.