ON EPISODIC MIGRATION AND ACCUMULATION OF HYDROCARBON
论幕式成藏

In the present paper are discussed the evidence, mechanism, characteristics and regularity of episodic migration and accumulation of hydrocarbon. 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, episodic migration and accumulation is also found to be an important type of reservoir formation and quite common in petroleum basins. Comparing 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. There existed 3 mechanisms for episodic migration and accumulation, namely, tectonic episodes (or tectonic pumping), seismic pumping (or fault valving) and overpressure building-up. 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 hydrocarbon migration and accumulation.