渤海海域中生界覆盖型潜山成藏认识与渤中13-2大油田发现

Recognition of oil and gas accumulation of Mesozoic covered buried hills in Bohai sea area and the discovery of BZ 13-2 oilfield

历经50余年勘探,渤海海域暴露型潜山已获得渤中19-6等多个大中型油气田发现,中生界覆盖型潜山一直未取得规模型勘探突破。近年来,针对制约覆盖型潜山勘探的成储和成藏问题展开了系统研究,取得了相关的地质新认识。认识到“垂向顶部差异、横向内幕连续”是大型变质岩潜山优质储集层分布模式,内幕网状裂缝型储层是覆盖型潜山主要储层类型,早、晚印支—燕山期多期应力叠加改造是优质储层形成的关键;提出“不整合—断层—网状缝”构成覆盖型潜山复式输导体系,“断面超压强注—网状缝高效输导”是覆盖型潜山主要成藏模式。新认识指导勘探实践,在渤中凹陷西南部中生界覆盖区发现了渤中13-2大型整装挥发性油田,实现了渤海海域覆盖型潜山勘探的领域性突破,打破了覆盖型潜山难以形成优质储层、难以规模成藏的传统认识,对于推动渤海湾盆地及近海其他盆地同类型潜山的勘探具有重要指导意义。

After more than 50 years of exploration,several large and medium-sized oil and gas fields including BZ 19-6,etc.have been obtained in the exposed buried hills in Bohai sea area.However no large-scale exploration breakthrough has been made in Mesozoic covered buried hills.In recent years,systematic research has been carried out on the reservoir accumulation and formation issues that limit the exploration of covered buried hills,with new geological understanding obtained.According to the research,“different top in vertical direction,continuous inside in lateral direction”is the distribution pattern of high-quality reservoirs in large-scale metamorphic buried hills,the inner reticular fractured reservoir is the main type of“covered”buried hills,and the key to the formation of high-quality reservoirs is the multi-stage stress superimposition in the early and late Indochina-Yanshanian period;it is proposed that“unconformity-fault-reticular fracture”constitutes the composite migration system of“covered”buried hills,and“fault surface overpressure injection-reticular fracture high efficient migration”is the reservoir forming model of buried hills.These new understandings were used to guide the exploration practice,with BZ 13-2 large integrated volatile oilfield discovered in the Mesozoic covered area in southwestern Bozhong sag,which is a breakthrough in the exploration of“covered”buried hills in Bohai sea area and breaks the conventional understanding that“covered”buried hills are difficult to form high-quality and large-scale reservoirs.It is of great significance to promote the exploration of the same type buried hills in other offshore basins of Bohai Bay basin.