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.

The search for oil, its development, production, and marketing have, for the better part of a century, been a fundamental part of the Texas economy. The history of Texas oil finders, from the self-educated wildcatter to the highly trained explorationist, is a part of Texas lore.

Characterization of 500 of the largest Texas oil reservoirs permits grouping into plays of similar geology and common engineering and production attributes.

Reservoirs in the Permian Basin of Texas are estimated to have contained a total of 105.7 billion barrels (Bbbl) of oil at discovery. As of January 1985, these reservoirs had produced a cumulative volume of 25.3 Bbbl of oil, and proved reserves were calculated at 5.9 Bbbl.

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.

The Leonardian Spraberry Formation is a major oil-producing formation of the Permian Basin, accounting for more than 700 million barrels of oil produced from heterogeneous submarine-fan reservoirs.

Continuity of sandstone reservoirs is controlled by various factors, including faults, sand-body geometry, and the distribution of framework grains, matrices, and interstices within the sand body.

Many modern shore zones comprise a continuum of depositional environments that encompass both strandplain and barrier-island systems. Strandplains are further subdivided into two classes: sand-rich beach-ridge plains and mud-rich chenier plains.

The Upper Cretaceous Olmos Formation in South Texas continues to be an active exploration target 60 years after oil was first discovered in this clastic assemblage. The shallow, oil-bearing formation was deposited on a broad, wave-influenced shelf. Sand accumulated in two depocenters.

The Big Wells (San Miguel) reservoir in Dimmit and Zavala Counties, South Texas, produces from a broadly lenticular, wave-dominated deltaic sandstone encased in prodelta and shelf mudstones.