Abstract: Upper Jurassic Smackover Carbonate Petroleum System, Gulf of Mexico, USA

MANCINI, ERNEST A

The Upper Jurassic Smackover Formation is one of the most prolific hydrocarbon carbonate reservoirs in the Gulf of Mexico. The Smackover represents a closed carbonate petroleum system. Source rocks, reservoir rocks, and seal rocks are all contained within this unit. The Smackover petroleum trap is generally structural or combination involving favorable stratigraphy (depositional lithofacies, diagenetic facies, unconformities, or pinchouts on paleotopographic basement features) and salt anticlines, diapiric salt anticlines, or extensional fault traps associated with salt movement. The source potential of the lower Smackover carbonate mudstones has been optimized by the combination of favorable conditions of deposition, preservation, and subsequent burial and thermal histories. These mudstones are marine source rocks containing ample amounts of algal and algal-derived amorphous kerogens. Reservoir-grade Smackover carbonate rocks include dolostones and leached and dolomitized packstones, grainstones, and boundstones. Porosity is facies-selective and is preserved in the high to moderate energy lithofacies of the upper part of the Smackover. Smackover diagenesis was dominated by the effects of early cementation, dissolution of carbonate grains, and dolomitization. Porosity types include interparticulate, shelter, intercrystalline dolomite, grain moldic, and vuggy. Anhydrites of the uppermost Smackover and overlying formation commonly form a regional seal for the petroleum trap. An understanding of the complexities of the Smackover petroleum system is crucial to successful prospecting for and production of the hydrocarbons contained in these carbonate rocks.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria