Reexploration of old fields in mature hydrocarbon provinces, such as the Permian Basin of West Texas and New Mexico, may significantly increase known oil and gas reserves.

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.

Petroleum reservoirs typically yield only a fraction of the oil initially in place because geologic heterogeneity causes incomplete drainage of oil. Accurately predicting oil recovery requires realistic estimates of interwell porosity and permeability patterns that are discontinuous in both the horizontal and the vertical direction.

In 1983, the Bureau of Economic Geology published the Atlas of Major Texas Oil Reservoirs, a precedent-setting synthesis of key geological and engineering data on 450 major oil reservoirs grouped into 48 regional plays. This volume, the Atlas of Major Texas Gas Reservoirs, is a companion to the earlier work.

The State-owned submerged lands of Texas encompass almost 6,000 mi2 (15,540 km2). They lie below waters of the bay-estuary-lagoon system and the Gulf of Mexico and extend 10.3 mi (16.6 km) seaward from the Gulf shoreline (fig. 1).