Since 1913, the Mervine field (T27N, R3E) has produced oil from 11 Mississippian and Pennsylvanian zones, and gas from two Permian zones. The field exhibits an asymmetric surface anticline, with the steeper flank dipping 30° east, maximum. A nearly vertical, basement-controlled fault occurs immediately beneath the steep flank of the surface anticline. Three periods of left-lateral wrench faulting account for 93% of all structural growth: 24% in the post-Mississippian to the pre-Desmoinesian; 21% in the Virgilian; and 48% in the post-Wolfcampian.

The Devonian Woodford Shale--and possibly the Desmoinesian Cherokee and Ordovician Simpson shales--locally generated oil in the Mesozoic through the early Cenozoic, which should have been structurally trapped in the Ordovician Bromide sandstone. This oil may have joined oil previously trapped in the Bromide, which had migrated to the Mervine area during the Early Pennsylvanian from a distant source. Intense post-Wolfcampian movement(s) fractured the competent pre-Pennsylvanian rocks, allowing Bromide brine and entrained oil to migrate vertically up the master fault and accumulate in younger reservoirs.

Pressure, temperatures, and salinity anomalies indicate that vertical fluid migration presently continues at Mervine field. Consequently, pressure, temperature, and salinity mapping should be considered as a valuable supplement to structural and lithologic mapping when prospecting for structural hydrocarbon accumulations in intracratonic provinces.

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