The Gas Research Institute, U.S. Department of Energy, and the State of Texas cooperated in joint-venture research to evaluate the infield reserve growth potential of mature gas fields containing conventional reservoirs.

Shallow-water-platform carbonate reservoirs of Permian age have accounted for more than half of the oil production in the Permian Basin, one of the largest oil-producing regions in the United States.

The Fort Worth Basin, in North-Central Texas, is a late Paleozoic foreland basin that was downwarped during the Early to Middle Pennsylvanian Period in response to tectonic stresses that also produced the Ouachita Thrust Belt.

Sandstone reservoirs deposited in microtidal barrier systems contain large oil and gas reserves in several Gulf Coast Basin plays.

Pervasively dolomitized, anhydritic carbonates of the upper San Andres Formation in the Emma field of West Texas constitute an upward-shallowing sequence of lithofacies representing four major depositional environments.

This study is a product of ongoing Bureau of Economic Geology investigations, by means of geologic and petrophysical modeling, into the nature of reservoir compartmentalization or heterogeneity.

Petroleum reservoirs typically yield only a fraction of the oil initially in place because geologic heterogeneity causes incomplete drainage of oil.

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.

Silurian and Devonian carbonate and chert rocks in the Permian Basin constitute a prolific hydrocarbon-bearing succession in West Texas and New Mexico.

This report documents research done on the mature and prolific McAllen Ranch gas field in South Texas, as part of the Secondary Gas Recovery (SGR) project funded by the Gas Research Institute, U.S.