ABSTRACT

The Trans-Pecos has intrigued and baffled the oil industry, and all exploratory efforts so far have remained fruitless. Our geophysical findings along with other geologic information allow us to analyze the overall hydrocarbon potential for this area.

Gravity and magnetic data were helpful in regional mapping but were unreliable for localized information owing to numerous extrusive and intrusive rocks.

Seismic mapping shows many undrilled structures. However, the success ratio for the structures already drilled is disappointing (e.g., on the Diablo platform, out of 22 structural leads, 11 have been drilled and all were dry, and in the Marfa basin 17 out of 41 leads were drilled without success). Results were similar in Salt-Flat graben. Many of these wells had good hydrocarbon shows and almost all yielded fresh water. Tectonically the area has undergone several periods of orogeny, the result of the latest being numerous Basin and Range faults. The area is still seismically active and shows appreciable geodetic movement. It is suggested that the traps were destroyed with subsequent leakage of hydrocarbon and repeated induction of fresh water. Trap destruction is apparently beyond the scope of seismic detection.

The Chihuahua trough (United States), in spite of many discouraging facts, such as high heat flow, thermal waters, etc, shows some promise because seismic data reveal large thrust anticlines in the lower Paleozoic rocks (approximately 15,000 ft) that are yet to be adequately tested.

Other smaller undamaged stratigraphic traps (reefs, truncations, pinch-outs, etc) are possibly present and could be targets for future exploration.

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