Trap Mechanism in the Southern Kra Basin, Gulf of Thailand

Abstract

This study will identify potential traps in the southern Kra Basin large structural closures and seismic geometries, and evaluate seal capacity by using fault character, fault throw and sand thickness cross plots. The main trap styles are northeast-southwest trending listric normal faults that extend into the post-rift reservoir as a product of basin subsidence. Faults usually trap hydrocarbons on their up-thrown sides. Reservoir successions from adjacent basins indicate a thickness range from thin sand (0.3m) to thick sand (73m), while fault throw varies from 30 m to 305 m. Fault throw and reservoir sand thickness cross plots indicate high fault seal probability, which suggests most fault throws completely offset reservoir sands, so the faults are sealing. Seismic character indicates lateral lithology changes from sand-rich successions on the basin flank to basinal shale-rich successions, with low to moderate amplitude and continuity on the flanks of the basin and moderate to high amplitude and continuity basinward. Fault traps have a high probability for trapping and sealing basinward, where there is thick shale and large fault throws. Traps on the basin edge have low potential because the area is sand-rich with small fault throws.