车排子凸起西南缘油气来源与成藏过程

Oil Source and Hydrocarbon Accumulation Process in Southwest of Chepaizi Uplift

车排子凸起紧邻两大生烃凹陷,由于烃源岩层多,油气来源尚不明确,为了进一步明确油气来源,对研究区的原油根据地球化学特征进行了分类,同时厘定了主力烃源岩的地化特征。研究结果表明:研究区的原油可以分为两类,其中Ⅰ类原油是氧化环境下高等植物来源的高成熟原油,主要来源于四棵树凹陷侏罗系烃源岩,Ⅱ类原油是氧化一还原环境下高等植物及藻类来源的较低成熟原油,主要来源于四棵树凹陷侏罗系烃源岩与白垩系或古近系源岩的混源。结合油气输导条件及区域构造背景演化,认为侏罗系/石炭系不整合底砾岩及沙湾组一段1砂组的"板砂"是油气横向运移的有利通道,而喜山期形成的正断层则是油气垂向运移的有利通道。

Chepaizi Uplift is adjacent to two hydrocarbon generation sags, in which oil sources were still unclear because there are several sets of source rocks. In order to clarify further about this, oils in studied area were classified based on their geochemistry characteristic. In addition, study has been conducted on the geochemistry characteristic of the major source rocks. The results shows that oils in studied area can be divided into two types, type I oils were mainly generated by terrenstrial higher plants in strong oxgen environment with higher maturity, and generated from Jurassic source rocks in Sikeshu sag; type II oils were mainly generated by terrenstrial higher plants and algae in oxidation-reduction environment with lower maturity, generated from Jurassic source rocks and Cretaceous source rocks or Paleogene source rocks in Sikeshu sag. Combined with study results on oil transportation system and structure evolution, it is believed that bottom conglomerate above the unconformity of Jurassic/Carboniferous and thick sand in Shawan Formation of Neogene are the main lateral long-distance hydrocarbon migration pathways, and normal faults developed in Himalayan period are the main vertical migration pathways.