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.

Horizontal drilling in a mature hydrocarbon province such as Texas can increase recovery from reservoirs in which a significant proportion of oil or gas in place remains unrecovered by conventional means.

This field guide summarizes recent interpretations of the upper Cenozoic stratigraphy of parts of the Southern High Plains and Rolling Plains in northwestern Texas and eastern New Mexico. Processes that formed lacustrine basins, which pond surface water on the High Plains that is recharged to the Ogallala aquifer. are also described.

Lower Permian Wolfcamp and Wichita carbonates and anhydrites in the Palo Duro Basin, Texas Panhandle, record a change from normal-marine to marine evaporite depositional environment. These strata also contain a widespread porous and permeable interval that currently comprises a deep-basin brine aquifer system.