柴达木盆地马海平顶山区断裂活动与油气运聚

Fracture activities and hydrocarbon accumulation in Pingdingshan area of Mahai,Chaidamu basin.

柴达木盆地马海平顶山地区目前发现的油气藏主要沿着马仙断裂带分布,油气的运移和聚集与断裂活动之间的关系密不可分。通过最新解释的三维地震资料,分析了断裂的平面和剖面展布特征,通过构造演化剖面厘定了断裂活动的主要时期,最终结合烃源岩、流体包裹体等研究成果,论述了断裂活动与油气的运移和聚集之间的配置关系。形成时间较早的马仙断裂早期为正断裂,在晚侏罗世—白垩纪发生反转,是马海平顶山地区主要的油源断裂;形成时间较晚(喜马拉雅运动中、晚期构造活动)的一系列派生的断裂体系构成了主要的构造圈闭。喜马拉稚运动中、晚期构造活动时期既是构造圈闭形成的主要时期,又是油气大规模运移时期,因此是马海平顶山地区油气成藏的关键期。研究认为,马海平顶山地区下一步勘探方向应立足于断裂带,沿断裂带寻找有效圈闭。

Up until now,reservoirs found in Mahai Area of Chaidamu Basin mainly distribute along Maxian fault zone.The migration and accumulation of hydrocarbon is closely related to the fracture activi- ties.Through the latest interpreted 3D seismic data,the distribu- tion features of fractures on both horizontal and vertical were ana- lyzed;and the main stage of fracture activities was identified by structural evolution profiles.Associated with the research results of hydrocarbon-source rocks and fluid inclusion,the allocation rela- tionship among fracture activities,hydrocarbon migration,and ac- cumulation was expounded.The Maxian fault formed at the early stage was a normal one and it reversed in Late Jurassic-Cretaceous period,forming the main oil-source fracture in Pingdingshan area. The series of derived fault system formed later(the middle and lat- er stage of Himalayan structural movement)constituted the main structural traps.The middle and later stage of Himalayan structur- al movement is the main period for forming structural traps and for the large-scale hydrocarbon migration.Therefore,it is the key stage of forming reservoirs in Pingdingshan area.The research in- dicates that the exploration of Pingdingshan area in the near future should emphasize on fracture zone and look for effective traps along the fracture zone.