Abstract

The northern Green Canyon/Ewing Bank region, northern Gulf of Mexico basin, contains the Oxfordian-Neogene (.), Tithonian-Neogene (.), Albian-Neogene (.), Turonian-Neogene (.), and Eocene-Neogene (.) petroleum systems. The systems encompass 42 fields or discoveries in the study area and include four subsalt discoveries. Essential elements of the systems include source shales of Oxfordian, Tithonian, Albian, Turonian, and Eocene age; Neogene siliciclastic turbidite reservoirs; allochthonous salt; and overburden strata ranging in age from Jurassic to Quaternary. The petroleum systems of the area are significantly affected by the evolution of allochthonous salt. The high thermal conductivity of salt retards the thermal maturation of subsalt petroleum source rocks and causes late generation and migration from them. Most traps were formed during the Pliocene-Pleistocene, and the generation-migration-accumulation of petroleum ranges from early Miocene to the Holocene. The critical moment of peak oil generation for each source varies spatially and temporally as a function of the overlying sediments and allochthonous salt evolution. The impermeability of salt prevents vertical petroleum migration and causes migration pathways to be deflected laterally up the dip of base salt. Where salt welds form, petroleum migration is unimpeded and continues vertically. By integrating predictions of potential source rocks, structural restorations, thermal maturation modeling, regional salt maps, and petroleum systems logic, we can determine petroleum migration pathways and zones of concentration. All 42 fields or discoveries within the study area are associated with predicted zones of paleosubsalt petroleum concentration. Present-day salt geometries do not delineate many of these zones because of salt weld formation during the Pleistocene. This generation, migration, and accumulation technique enables geoscientists to focus their exploration efforts toward areas with a greater probability of success.

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