北部湾盆地迈陈凹陷油气成藏地质特点及油气藏类型

Hydrocarbon Accumulation Characteristics and Reservoir Types of Maichen Sag in Beibuwan Basin

通过对北部湾盆地迈陈凹陷东部烃源岩条件、沉积体系、储盖组合等方面的分析,结果表明:迈陈凹陷具有两类烃源岩供烃,分别为流沙港组湖相烃源岩和涠洲组发育的煤系烃源岩;两个物源方向,北部斜坡带以发育大型河流—三角洲沉积体系为主,南部断裂带以发育多期上下叠置的水下扇为主,形成南北不同的沉积体系;两套储盖组合,分别为流沙港组储盖组合和涠洲组储盖组合。由于烃源来源、沉积体系、储盖组合以及圈闭类型的多样性,在不同区带的油气藏类型也有所不同,北部斜坡带以受断层控制的断鼻—断块型油气藏为主,而南部断裂带则以扇控型隐蔽油气藏为主。

Through analysis of source rocks, sedimentary system and reservoir seal assemblage of eastern Maichen sag in Beibuwan Basin, it is revealed that there are two kinds of source rocks in Maichen sag, including lacustraline facies source rock in Liushagang formation and coal-bearing source rocks in Weizhou formation. There are two sets of different sedimentary systems including large rivers-delta depositional system in north slope zone and multi-phase superimposed underwater fans in southern fault zone. There are two sets of reservoir-cap combination, Liushagang Fm reservoir-cap combination and Weizhou Fm reservoir-cap combination. Because of the diversity in hydrocarbon sources, sedimentary systems, reservoir-cap combinations and trap type, reservoir types are quite different in different place such as faulted nose-fanlt block reservoirs controlled by faults in north slope zone and subtle reser- voirs controlled by fans in southern fault zone.