A basin modeling study on the coupling of fault activity and hydrocarbon accumulation in the Baiyun Sag

The Baiyun Sag is located in the northern passive continental margin of the South China Sea. The widespread faults around the sag affect the migration and accumulation of hydrocarbon profoundly. Faults control the sedimentation of source rocks from the Eocene to the Early Oligocene, regulate the range of reservoirs from the Late Oligocene to the Middle Miocene and dominate the seals and traps during the reactivation period in the Late Miocene. We attempt to study the controls of fault activity on hydrocarbon migration and accumulation through faults sealing analysis and basin modeling. Results are as follows.(1) The episodes of fault activity couple well with the generation of hydrocarbon.(2) Overpressure due to hydrocarbon generation may accelerate faulting activity at ~18.5 Ma.(3) Active faults act as perfect conduits for vertical migration of hydrocarbon.(4) Shale smear is much more credible in reflecting the sealing ability of motionless faults than the simple fault activity analysis.(5) The southern faulted area in the deep water tends to be more favorable for hydrocarbon accumulation than the northern area.