Gas Potential of Deeply Buried Mesozoic Facies and Reservoirs in the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico
Ernest A. Mancini1, Donald A. Goddard2,
Peng Li1, and Victor Ramirez1
1 Box 870338, Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama 35487
2 Louisiana State University, Baton Rouge, Louisiana 70803
Deeply buried (>15,000 ft) Mesozoic facies and reservoirs in the onshore interior salt basins of the north central and northeastern Gulf of Mexico have high potential for significant gas resources. In the North Louisiana Salt Basin, potential deeply buried reservoirs include Upper Jurassic (Smackover, Cotton Valley) and Lower Cretaceous (Hosston, Sligo) facies. The estimate of secondary, non-associated thermogenic gas generated from cracking of oil in the source rock from depths below 12,000 ft is 4800 trillion cubic ft (TCF). Assuming an expulsion, migration and trapping efficiency of 1 to 5%, 48 to 240 TCF of gas is potentially available. Some 29 TCF of gas have been produced from this basin. In the Mississippi Interior Salt Basin, potential deeply buried reservoirs include Upper Jurassic (Norphlet, Smackover, Haynesville, Cotton Valley) and Lower Cretaceous (Hosston, Sligo) facies. The estimate of secondary non-associated gas generated from cracking of oil in the source rock from depths below 16,500 ft is 2350 TCF. Assuming an efficiency of 1 to 5%, 23.5 to 117.5 TCF of gas are potentially available. Some 13 TCF of gas have been produced from this basin. The thermogenic gas, whether generated from late secondary cracking of oil to gas in the source rock or from oil to gas conversion in deeply buried reservoirs in these basins migrated updip and vertically into shallower reservoirs at depths of some 2000 ft. The Manila and Conecuh subbasins are oil-prone. Although these subbasins are thermally mature for oil generation and expulsion, they are not thermally mature for secondary, non-associated thermogenic gas generation and expulsion.
AAPG Search and Discover Article #90069©2007 GCAGS 57th Annual Convention, Corpus Christi, Texas