论幕式成藏

ON EPISODIC MIGRATION AND ACCUMULATION OF HYDROCARBON

讨论了幕式成藏的证据、机理、规律及其勘探意义。指出幕式成藏是一种快速、高效的成藏方式,并常常具有周期性,因而对于高富集度大中型油气田的形成具有十分重要的意义;幕式成藏的机理主要有构造幕和构造泵作用、断层阀效应或地震泵作用以及超压积聚效应等3种作用。认为幕式成藏也是含油气盆地一种普遍存在的成藏方式,特别是对于多构造运动、断裂发育的盆地以及异常压力比较发育的盆地,幕式成藏往往占有重要地位;幕式成藏在时间上并不完全受生烃窗控制,而主要受控于区域构造运动、断裂活动或异常压力的演化,因此盆地的构造演化史、断裂活动史和异常压力发育史往往决定了幕式成藏史。

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.