Oil Source and Hydrocarbon Accumulation Process in Southwest of Chepaizi Uplift

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; typeⅡoils 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.