Mesozoic Carbonate Petroleum Systems in the Northeastern Gulf of Mexico Area
Published:December 01, 2001
Ernest A. Mancini, Marcello Badali, T. Markham Puckett, Juan Carlos Llinas, William C. Parcell, 2001. "Mesozoic Carbonate Petroleum Systems in the Northeastern Gulf of Mexico Area", Petroleum Systems of Deep-Water Basins–Global and Gulf of Mexico Experience, R.H. Fillon, N.C. Rosen, P. Weimer, A. Lowrie, H. Pettingill, R.L. Phair, H.H. Roberts, H.H. van Hoom
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Jurassic, Cretaceous, and Miocene deposits are productive of hydrocarbons in the Outer Continental Shelf (OCS) area of the northeastern Gulf of Mexico. Based on regional studies of the onshore and offshore shelfal areas, Upper Jurassic and Lower Cretaceous carbonates are projected as viable petroleum reservoirs in the continental slope areas of the northeastern Gulf of Mexico.
The primary petroleum source rocks for these Mesozoic petroleum reservoirs are believed to be Oxfordian to Kimmeridgian carbonates and Aptian to Albian carbonates and shales. Tithonian shales and carbonates are effective source rocks in Mexico and therefore may also have source potential in the OCS area. The Upper Jurassic source beds are postulated to be natural gas and condensate prone in the OCS area of the northeastern Gulf of Mexico, while the Lower Cretaceous source beds are believed to be oil prone. The natural gas and condensate produced from the Lower Cretaceous (Aptian) James Limestone in the OCS shelfal area is speculated to be sourced from Upper Jurassic (Smackover) carbonates, and the oil produced from Cretaceous (Albian and Cenomanian) Washita carbonates in the OCS shelfal area is believed to be sourced from Lower Cretaceous (post-James) carbonates and shales.
The principal carbonate petroleum reservoirs in the continental slope areas of the northeastern Gulf of Mexico are postulated to be Upper Jurassic deep-water microbial buildups (boundstones) developed on the outer portion of a carbonate ramp. Lower Cretaceous rudist reef rudstones and boundstones and slope carbonate deposits comprised of forereef debris rudstones and shelf-derived grainstones are believed also to have high reservoir potential in this area. Such deeper water deposits have been observed from seismic reflection profiles located seaward of the Lower Cretaceous rimmed shelf margin. Diagenetic studies of the Washita carbonate reservoirs in the OCS Main Pass Block 253 Field indicate that these reservoirs have been subjected to favorable diagenetic processes of dolomitization, dissolution and karstification associated with repeated exposure of the Cretaceous shelf margin.
Seismic reflection profiles indicate the presence of salt-related structures and paleotopographic basement features in the northeastern Gulf of Mexico. Petroleum traps in this region, therefore, are postulated to be combination traps involving favorable stratigraphic relationships and salt tectonics. The timing of hydrocarbon generation, expulsion, migration and entrapment appears favorable for petroleum accumulation.
Therefore, the continental slope areas of the northeastern Gulf of Mexico appear to have high potential for successful hydrocarbon exploration and development.