Abstract:Fault block pools distributed under source rock were discovered in the early Eocene third member of Liushagang formation in Wushi sag,Beibu Gulf basin,and oil derived from overlay overpressured and matured second member of Liushagang formation.Main controlling factor of hydrocarbon accumulation were pore fluid pressure difference between source rock and reservoir,sedimentary micro-facies and valid trap.Pore fluid pressure difference between source rock and reservoir controlled hydrocarbon migration direction,and made hydrocarbon migrated from second member of Liushagang formation downward to third member of Liushagang formation,then accumulated in the fault block trap belt.Otherwise,overpressured second member of Liushagang formation played sealing role for pool of third member of Liushagang formation.Braided channel conglomerate sandstone reservoir of middle part of subacqueous fan had good reservoir property,which was sweet spot reservoir.Pooling model of third member of Liushagang formation was characterized by overpressured source rock made hydrocarbon migrated downward,meanwhile acted as sealing rock,and source rock contacted with reservoir.Fault-related trap belts during Eocene rift episode were favorable hydrocarbon accumulation trend in the eastern part of Wushi sag.