Geologic evolution and structural controls on hydrocarbon flow in the Ship Shoal block 274/293 field, offshore Louisiana, Gulf of Mexico

This project involved interpreting the geometry and development of a salt-withdrawal basin in the Ship Shoal South additions. In addition, an analysis of the structure of the Ship Shoal 274/293 field was conducted to complement work by others in the field.; A salt-withdrawal basin dominates the southwest Ship Shoal South additions. The basin is flanked to the south by salt diapirs. To the north, east and west, the basin is bounded by generally continuous salt ridges. Arcuate normal faults separate the salt-withdrawal basin from the surrounding salt ridges to the north, east and west. Dipping steeply into the basin, these faults coalesce to form an arched-shaped fault system opening to the south. Maximum observed throw of these syndepositional faults is nearly 200 m and generally occurs at around 3000 m depth subsea, (about 2.5 second twt).; Basin development began prior 2.2 Ma, when the prograded shelf margin triggered salt migration. As subsidence continued, shelf progradation stalled and deposition of sediments reached a maximum rate of just under 2.0 mm/yr at 1.2 Ma. Accommodation was filled by 0.4 Ma. Volumetric calculations and basin reconstruction techniques suggest that 40–55% of the original allochthonous salt volume either dissolved or moved out of the survey area.; The Shell Offshore Inc. reservoirs located in Ship Shoal blocks 274 and 293 produce from fault-compartmentalized sand intervals. Sand groups D, F and G were mapped using the brightest negative amplitude corresponding to sands recorded on well data. Amplitude extraction showed a series of lineaments separating bright producing sands from dim water-bearing sands and shale. Lineaments on the dip, azimuth, dip/azimuth, and edge detection plots correspond to NE-SW striking faults that appear to control reservoir compartmentalization. Combining dip/azimuth plots of producing intervals with velocity data from sonic logs suggests that the throw of compartmentalizing faults is 15–25 m. Electric log, drainage area calculations, and dip variations observed in diameter data corroborate this interpretation.; The abrupt change of amplitude across the smaller faults matches production variations in the field. This suggests these faults seal and compartmentalize petroleum reservoirs. Parallelism of small-displacement faults with regional, large-displacement faults suggests genetic affinity.