ABSTRACT

The Shell Offshore, Inc. reservoirs located in Ship Shoal blocks 274 and 293 produce from fault-compartmentalized sand intervals. Faulting associated with salt tectonics controls hydrocarbon type and location.

The A-J reservoirs are a series of sand intervals each containing several smaller sand layers. Sand groups D, F and G were mapped using the brightest negative amplitude corresponding with the same sand interpreted on well data. Amplitude extraction shows a series of lineaments separating bright producing sands from dim water bearing sands and shale. Lineaments correspond to NE-SW striking faults that appear to control compartmentalization of the reservoir. Combining dip/azimuth plots of the producing intervals with velocity data from sonic logs suggests that the throw of these faults is 15-25 m. Electric log 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 and suggests these faults seal and compartmentalize production. This interpretation is supported by production of oil updip from gas in areas where amplitudes indicate faulting. Parallelism of small-displacement faults and regional, large-displacement faults suggests genetic affinity.