Mechanism of Controlling of Fault on Oil Accumulation in Laizhouwan Sag in Southern Bohai Bay Basin

Laizhouwan sag is the hydrocarbon-rich sag controlled by the multi-episode movements of Tanlu fault.The fault evolution has important effects on the hydrocarbon generation,migration and accumulation in the sag.The rapid subsidence in the faulted period caused development of high-quality source rocks of E2s41 and E2s2 3.At the same time,the fault communicating with deep thermal source allows it to flow up,leading to high geothermal gradient which accelerated the maturity evolution of the source rocks.So the fault becmes advantageous channels for vertical hydrocarbon migration,and controls the vertical expulsion of hydrocarbons.The late intense fault activities have certain destructive effects on the early preexisting oil and gas reservoirs.