冀中坳陷斜坡带奥陶系潜山油气成藏条件分析

研究工作依据实际资料和新的地质认识,对冀中坳陷文安斜坡和杨村斜坡奥陶系潜山带的构造格局及古潜山油气藏的形成条件进行了剖析。该区发育有正向和反向正断层,奥陶系地层形成一个地垒状潜山带,上覆石炭—二叠系地层,具有新生—古生—古储—中堵的成藏条件。石炭—二叠系煤系和下第三系泥岩为供烃源;不整合面、断面及北西向断裂为供油通道。油气成藏的主力因素储层的发育明显受白云石化、岩溶和构造破裂作用的控制,喜马拉雅期的岩溶作用是由活动断层导入岩溶水而得以进行的,因此,孔隙、裂隙相对富集的岩层与活动断层的匹配是潜山储层形成的关键地质条件。潜山古风化壳并不是制约储层发育的唯一因素。对该类储层的评价应构造分析与地层分析相结合。储集条件影响了油气的富集,长期活动的大断裂控制了油气的分布。

HYDROCARBON ACCUMULATION CONDITIONS OF THE ORDOVICIAN BURIED HILLS IN THE SLOPE ZONE OF THE JIZHONG DEPRESSION

According to the firsthand data and new geological study, the structural framework and the forming condition of buried hill reservoirs are analysed at the slope zone in the Jizhong depression. The obverse and reverse normal fault forms the horst buried hill zone. The block buried hills zone is covered by the Carboniferous Permian strata, which have the pools conditions with the neosource paleosource and paleoreservoir mesoblocking. Source rocks are composed of the Carboniferous Permian coal bearing rocks and Paleogene mudstone. Unconformities, fractures and SW faults act as the oil gas channels. The development of reservoirs are controlled by dolomitization, karstification and fracturing. The Himalayan karstification results from the action between the dissoluble rocks and water induced by active faults. So the match between rocks with rich porosity, fractures and active faults is the key geological factor of the formation of the buried hills reservoir. The oil gas accumulation is influenced by reservoirs condition. The distribution of oil gas is controlled by long term active faults. Paleo weathered crust is not the unique factor to control the development of reservoirs. The evaluating about these buried hill reservoirs should link the structures with strata.