ABSTRACT

Three Jurassic natural gas trends can be delineated in southwestern Alabama and the Florida panhandle area. These include a deep natural gas trend, a natural gas and condensate trend, and an oil and associated natural gas trend. Trends are recognized by hydrocarbon types, basinal positions, and relationships to regional structural features. Within these natural gas trends, eight distinct natural gas plays can be identified. Plays are recognized by characteristic hydrocarbon traps and reservoirs.

The deep natural gas trend includes the Mobile Bay area play that is characterized by structural hydrocarbon traps associated with salt tectonism and Norphlet sandstone reservoirs at depths exceeding 20,000 feet. The natural gas and condensate trend includes the Mississippi interior salt basin play, the Mobile graben play, the Wiggins arch complex play, and the Pollard fault system play. The Mississippi interior salt basin play is typified by salt-related structural and combination hydrocarbon traps and Smackover dolomitized oolitic, oncolitic, and peloidal grainstone and packstone reservoirs at depths of approximately 16,000 feet. The Mobile graben play is exemplified by salt-induced structural hydrocarbon traps and Smackover dolostone and Norphlet sandstone reservoirs at depths ranging from 12,400 to 18,400 feet. The Wiggins arch complex play is characterized by structural and combination hydrocarbon traps associated with stratigraphic pinch-outs and salt flow. These traps are salt-related and occur along the flanks of paleohighs associated with the Wiggins arch complex. Smackover dolostone reservoirs at depths ranging from 16,100 to 18,400 feet are typical of this play. The Pollard fault system play is typified by salt-induced structural hydrocarbon traps and reservoirs at depths of approximately 15,000 feet. These reservoirs are Smackover dolomitized oolitic and peloidal grainstones and packstones and Norphlet sandstones. The oil and associated natural gas trend includes the Gilbertown and West Bend fault systems play, the Foshee fault system play, and the basement ridge play. The Gilbertown and West Bend fault systems play is exemplified by salt-related structural or combination traps and Smackover dolomitized oolitic, oncolitic, and peloidal grainstone and packstone reservoirs and Norphlet sandstone reservoirs at depths ranging from 11,000 to 14,000 feet. The Foshee fault system play is characterized by structural and combination hydrocarbon traps related to salt movement and Smackover dolomitized peloidal grainstone and packstone and Norphlet sandstone reservoirs at depths of approximately 15,000 feet. The basement ridge play, which is typified by structural and combination traps associated with the Conecuh and Pensacola-Decatur ridge complexes and Smackover oolitic and peloidal grainstone and packstone and algal boundstone and Haynesville sandstone reservoirs at depths ranging from 11,800 to 15,500 feet, has potential for significant undiscovered natural gas.