THE EFFECT OF ALLOCHTHONOUS SALT ON THE PETROLEUM SYSTEMS OF NORTHERNGREEN CANYON AND EWING BANK (OFFSHORE LOUISIANA), NORTHERN GULF-OF-MEXICO

The northern Green Canyon/Ewing Bank region, northern Gulf of Mexico b asin, contains the Oxfordian-Neogene (.), Tithonian-Neogene (.), Albia n-Neogene (.), Turonian-Neogene (.), and Eocene-Neogene (.) petroleum systems. The systems encompass 42 fields or discoveries in the study a rea and include four subsalt discoveries. Essential elements of the sy stems include source shales of Oxfordian, Tithonian, Albian, Turonian, and Eocene age; Neogene siliciclastic turbidite reservoirs; allochtho nous salt; and overburden strata ranging in age from Jurassic to Quate rnary. 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 f ormed during the Pliocene-Pleistocene, and the generation-migration ac cumulation of petroleum ranges from early Miocene to the Holocene. The critical moment of peak oil generation for each source varies spatial ly and temporally as a function of the overlying sediments and allocht honous salt evolution. The impermeability of salt prevents vertical pe troleum migration and causes migration pathways to be deflected latera lly up the dip of base salt. Where salt welds form, petroleum migratio n is unimpeded and continues vertically By integrating predictions of potential source rocks, structural restorations, thermal maturation mo deling, regional salt maps, and petroleum systems logic, we can determ ine petroleum migration pathways and zones of concentration. All 42 fi elds or discoveries within the study area are associated with predicte d zones of paleosubsalt petroleum concentration. Present-day salt geom etries do not delineate many of these zones because of salt weld forma tion during the Pleistocene. This generation, migration, and accumulat ion technique enables geoscientists to focus their exploration efforts toward areas with a greater probability of success.