Summary

Several long-standing problems in the Delaware Basin have intrigued geologists for years, including (1) why petroleum and mineral reservoirs are found along basin's margins, (2) why large fluid pressures exceeding hydrostatic sustain in this tectonically stable basin where there has been insignificant sedimentation for the last 250 million years. To address these questions, we reconstructed the hydrologic evolution of the Delaware Basin by quantitative modeling techniques. Our results show that overpressure may develop in response to sediment compaction during the late Permian time. The preservation of the ancient overpressure to the present, however, requires the presence of a extremely low-permeability (< 10^-11 darcy) top seal. The sulfur ore deposits in the western basin likely formed in a fluid mixing zone established from the Laramide orogeny. In our model, meteoric water recharged along the basin's uplifted western margin and discharged basinward. Hydrocarbon and deep basin fluids migrated landward through the Third Sand regional aquifer and then upwelled along faults along the basin's western margin. The hydrocarbon reacted with anhydrite/gypsum in evaporite beds and mixed with meteoric water, resulting in a biochemical reaction that formed sulfur deposits.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah