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. Since discovery in 1927 the unit has produced 43 million barrels of primary and waterflood oil of an estimated 164 million barrels of original oil in place. Approximately 30 million barrels of mobile oil remains in the main reservoir of this unit.

 4 oversized sheets, Lambert Conformal Conic projection based on standard parallel 33 degrees and 45 degrees. Accompanied by a text booklet, The Tectonic Framework of Texas.

Geologic mapping and fracture analysis of the Lower Cretaceous Edwards aquifer strata near Georgetown and Round Rock, Texas, were performed to provide a better understanding of the geologic framework of the Balcones Fault Zone and to provide information for assessing ground-water flow characteristics. Cretaceous strata dip gently eastward and are locally overlain by terrace deposits and alluvium. Several major normal faults, downthrown to the east, strike northward across the area. Gentle flexures, possibly related to faulting, parallel the faults.

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. In this study, we combine lithologic, mineralogic, and petrographic evidence of depositional conditions with the isotopic compositions of carbon, oxygen, sulfur, and strontium to determine the geochemical conditions during deposition and diagenesis.