Primary basins and their boundaries in the deep-water northern Gulf of Mexico: Origin, trap types, and petroleum system implications

Abstract

Primary basins form stratigraphically continuous successions on autochthonous salt and, therefore, in the northern Gulf of Mexico, contain all the components of a petroleum system (source, reservoir, trap, and seal). Most primary basins are encased entirely in salt or in some combination of salt and welds. Petroleum exploration in the deep-water Gulf of Mexico is currently focused on primary basin targets and increasingly those at their lateral boundaries. However, as these boundaries are commonly poorly imaged, robust structural models are critical to interpretation of their structural evolution and relative petroleum system risk. Using three-dimensional seismic data, we define three tectonostratigraphic provinces that characterize primary basin depocenters: (1) a disconnected salt-stock-canopy province in Mississippi Canyon; (2) an amalgamated salt-stock-canopy province in northern Atwater Valley, southeastern Green Canyon, Walker Ridge, and southern Keathley Canyon; and (3) a bucket-weld province in western Green Canyon, Garden Banks, and northern Keathley Canyon. We recognize six trap types in the primary basins: (1) autochthonous salt-cored folds, (2) turtle structures, (3) base-of-salt truncations, (4) salt feeders, (5) salt ridges, and (6) bucket welds. Most primary basin explorations to date have targeted traps in one of the first four styles. Future primary basin exploration will increasingly focus on the traps formed by bucket welds and salt-cored ridges. The contrasting evolution of these features has implications for reservoir continuity, charge access, and trap configuration. Of primary basin boundary trap types, salt feeders have the lowest petroleum system risk followed by bucket welds, with salt-cored ridges having the highest risk.