Evaluation of large areas requires a different approach from that used to develop prospects. Regional cross-section networks generally ignore minor correlation problems. We examined and related all potentially significant parameters, and used reduced scales to subdue nonessentials and to cover a large area. Organization and planning must permit free interchange of ideas and close cooperation among those working on the project.

Regional structural and stratigraphic analysis of Trans-Pecos Texas strongly suggests that widespread trap-destruction by faulting and erosion led to hydrocarbon leakage and induction of fresh water into prospective zones, which reduced the likelihood of accumulation and preservation of economic reserves.

At least 4 major periods of tectonism, pervasive fresh water, mineralization, basic igneous intrusives and extrusives, high heat-flow regime, increasing percentage of carbon dioxide southwestward from the Delaware basin, and contemporaneous vertical movement suggest that the opportunity for major reserves is minimal.

A review of 1,000 mi of CDP seismic data from 4 areas disclosed 65 structural leads or traps, of which 45 had significant tests. All these tests were failures; many gave indications of sizable amounts of fresh water.

None of the areas have been completely condemned. However, only relatively small reserves can be anticipated for nearshore to continental Jurassic and Cretaceous sections in the Chihuahua Trough, Pennsylvanian and Permian reefs formed on a shelf environment or on the flanks of major uplifts, or in areas such as the Marfa basin.

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