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Since the discovery of oil in 1967 from the Smackover Formation at Toxey field, Choctaw County, Alabama, and of condensate in 1968 from the Norphlet Formation at Flomaton field, Escambia County, Alabama, the Upper Jurassic has become the primary exploration target in southwestern Alabama. Following those initial discoveries, 39 Upper Jurassic fields have been established in Alabama, but only in 4 of these has the Norphlet produced hydrocarbons. The discovery of productive Norphlet gas sandstones in 1979 at the Lower Mobile Bay-Mary Ann field, offshore Alabama, has demonstrated the potential of the Norphlet in the central and eastern Gulf of Mexico regions. All 4 wells drilled to test the Norphlet in Mobile Bay have been successful gas wells, and have tested between 10.5 a d 19.4 mmcf per day. Although drilling is to depths exceeding 20,000 ft (6,100 m) subsea, the projected gas reserves justify continued exploration.
Norphlet petroleum traps in the region are principally combination traps involving favorable stratigraphy and salt anticlines (Copeland field), extensional fault traps associated with salt movement (Flomaton field), and faulted salt anticlines (Hatter's Pond and Lower Mobile Bay-Mary Ann fields). Reservoir rocks include marine, dune, and fluvial sandstone lithofacies. Sandstone porosity involves both primary intergranular and secondary dissolution and fracture. Smackover algal carbonate mudstone is probably the source for much of the Norphlet hydrocarbon, but downdip Norphlet marine shales may also be source rocks.
The central and eastern Gulf of Mexico regions should continue to be excellent areas to explore for hydrocarbons in the years ahead. Successful Norphlet petroleum prospecting in the area has involved the identification of favorable sandstone lithofacies and structural hydrocarbon traps by using geologic and geophysical methods. Future Norphlet discoveries will require the delineation of stratigraphic and structural/stratigraphic combination hydrocarbon traps using seismic-stratigraphic techniques.
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