ABSTRACT: Natural Gas Plays in Jurassic Reservoirs of Southwestern Alabama and the Florida Panhandle Area

Ernest A. Mancini, Robert M. Mink, Berry H. Tew, Bennett L. Bearden

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

The deep natural gas trend includes the Mobile Bay area play, which is characterized by faulted salt anticlines associated with the Lower Mobile Bay fault system and Norphlet eolian sandstone reservoirs exhibiting primary and secondary porosity at depths exceeding 20,000 ft. The natural gas and condensate trend includes the Mississippi Interior Salt basin play, Mobile graben play, Wiggins arch flank play, and the Pollard fault system play. The Mississippi Interior Salt basin play is typified by salt anticlines associated with salt tectonism in the Mississippi Interior Salt basin and Smackover dolomitized peloidal and pelmoldic grainstone and packstone reservoirs at depths of approximately 16,000 ft. The Mobile graben play is exemplified by faulted salt anticlines associated with the M bile graben and Smackover dolostone reservoirs at depths of approximately 18,000 ft. The Wiggins arch flank play is characterized by structural traps consisting of salt anticlines associated with stratigraphic thinning and Smackover dolostone reservoirs at depths of approximately 18,000 ft. The Pollard fault system play is typified by combination petroleum traps. The structural component is associated with the Pollard fault system and reservoirs at depths of approximately 15,000 ft. These reservoirs are dominantly Smackover dolomitized oomoldic and pelmoldic grainstones and packstones and Norphlet marine, eolian, and wadi sandstones exhibiting primary and secondary porosity. The oil and associated natural gas trend includes the Gilbertown-West Bend fault system play, the Foshee fault sys em play, and the Conecuh basement play. The Gilbertown-West Bend fault system play is exemplified by faulted salt anticlines associated with the Gilbertown-West Bend fault system and Smackover oolitic grainstone reservoirs at depths of approximately 11,000 ft. The Foshee fault system play is characterized by combination petroleum traps with the structural component associated with the Foshee fault system and Smackover peloidal grainstone and packstone reservoirs at depths of approximately 15,000 ft. No significant quantities of natural gas have been discovered in the Conecuh basement play, which is typified by structural traps associated with the Conecuh ridge and other paleohighs and Smackover grainstone and Haynesville sandstone reservoirs; however, this play has potential for signific nt undiscovered natural gas resources.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990