THEORY OF EPISODIC MIGRATION AND ACCUMULATION：EVIDENCE AND EXPLORATION SIGNIFICANCE

It is evidenced that episodic migration and accumulation is rapid,efficient and periodic as a kind of reservoir formation,and therefore significant to the formation of mid-large oil and gas fields.Like gradual migration and accumulation of hydrocarbon,episodic migration and accumulation is also found to be quite common type of reservoir formation in petroleum basins.Compared with gradual migration and accumulation,episodic migration and accumulation is particularly important in basins that experienced strong orogenies,fault activity or have abnormal pressures.Unlike gradual migration and accumulation,which is more important in cratonic basins,episodic migration and accumulation is more important in foreland and rift basins.It should be noted that episodic migration and accumulation is not fully controlled by hydrocarbon generation window in time,but mainly by tectonic events (fault activity in particular) and evolution of abnormal pressure as well.Consequently,history of tectonic changes,fault activity and/or abnormal pressure development determine that of episodic migration and accumulation.The theory of episodic migration and accumulation is not only an important supplement to the traditional theory of petroleum geology,but also broads the exploration domain and further defines the exploration orientation of mid-large oil and gas fields.