Development of a predictive model for porosity distribution in the Smackover Formation of southwest Alabama. Final report, 1983-1984

Technical Report · Thu Nov 15 00:00:00 EST 1984

OSTI ID:6037579

Benson, J

The Upper Jurassic Smackover Formation is the major hydrocarbon producer in the State of Alabama having produced over 69.5 million bbls of oil, 63 million bbls of condensate, and 237 million Mcf of gas since the initial Smackover discovery from Toxey Field, Choctaw County in 1967. Smackover hydrocarbon exploration is hampered in Alabama and throughout the Gulf Coast by the inability to effectively predict porosity distribution in the unit. This report represents the results of the first year of a study designed to develop a predictive model for porosity distribution in the Smackover of southwestern Alabama. This study is based on analysis of over 900 thin-sections from 70 wells in southwest Alabama. Eight lithofacies were recognized in the Smackover in the study area. These are: anhydritic mudstone, microcrystalline dolomite, oolitic grainstone, skeletal-peloidal grainstone/packstone, algal boundstone, finely-crystalline dolomite, coarsely-crystalline dolomite, and mudstone. Depositional porosity in the Smackover ranged from very high in the oolitic grainstone lithologies to very low in the mudstone lithologies. This depositional porosity, however, has been significantly modified by diagenesis. Smackover sediments have undergone a complex history of diagenetic modification which has included micritization, multi-stage cementation, multi-stage dissolution, dolomitization, and sulfate mineralization. These diagenetic processes have occluded primary porosity and, in some cases, produced secondary porosity in lithologies which lacked primary porosity. Four primary pore types have been recognized in the Smackover; primary interparticulate, oomoldic, dolomitic intercrystalline, and vuggy. The occurrence of these pore types indicates porosity distribution is controlled by paleotopography which significantly influenced depositional and diagenetic processes. 20 references, 14 figures.

• Research Organization: Alabama Univ., University (USA). Dept. of Geology
• OSTI ID: 6037579
• Report Number(s): NP-5900700; ON: TI85900700
• Country of Publication: United States
• Language: English

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