Abstract: Basement Control of Oil and Gas Traps: More Common than We Thought?

S. Parker Gay Jr.

Mapping of the basement fault block pattern in 18 petroleum basins throughout the U.S. since 1982 has revealed literally hundreds, of correlations of aeromagnetically defined basement faults, or shear zones, and oil and gas traps and structures. These range from simple fault traps, to horst blocks, to dolomitized fracture systems, to asymmetrical folds over reverse faults. Additionally, many types of stratigraphic traps correlate with basement shear zones. Some examples are Cretaceous algal mounds in the Paradox Basin that evidently formed on fault scarps on the sea floor, oolite shoals in Kansas also on subsea fault scarps, and offshore sand bars in the Powder River Basin that formed over fault-related sea floor highs. A separate important category of basement-related oi and gas traps are gravitationally-induced compaction structures, or graviclines, over basement hills.

A popular well chart by N. J. Hyne published in 1984 lists 29 basic types of oil and gas traps. Of these 29, our studies demonstrate that 20 of them (69%) can, and do, result from basement control. We will show actual field examples of many of these categories.

Basement control is thus very real and very pervasive in structural and stratigraphic geology, and although it is not a subject we learn in college or even in professional short courses, it is an important factor in the formation of a high percentage of oil and gas traps and reservoirs.

AAPG Search and Discovery Article #90952©1996 AAPG Rocky Mountain Section Meeting, Billings, Montana