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.

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. Such drilling has been particularly effective in increasing production where production is from natural fiactures, such as in the Pearsall field of the Austin Chalk trend in South Texas. Production can also be enhanced where the reservoir-quality

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.

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. Field trip stops were selected to illustrate the depositional facies and paleosols of Cenozoic formations, Cenozoic local faunas, and lacustrine basins.

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. Data from old wells are being reevaluated in light of current oil and gas prices using new geologic and engineering reservoir models, in discovery of untapped hydrocarbn-producing zones.