Distribution Of Jurassic Effective Source Rocks In The Yabrai Basin And Its Control To Petroleum

This paper made the Jurassic of Yabrai Basin as the study object.Firstly,the author analyzed the organic matter abundance,type and thermal evolutionary characteristic of Jurassic source rock on the basis of the TOC,Rock-Eval pyrolysis and organic petrology data,and made clear the main source rock layers.According to the basic principle of hydrocarbon generation and expulsion,the author determined the TOC lower limit of effective source rock,by using the relation of TOC content with S1 content.Then the author recognized and statisticed the thickness and determined the distribution characteristics of the effective source rock,referring to sedimentary facies and formation thickness.Besides,the author studied petroleum accumulation model of Yabrai Basin Jurassic according to reservoir features and the source-reservoir configuration relations.Finally,the author made sure the influence of the effective source rock to petroleum layers.The research results show that the organic matter abundance and type are poor in the Middle Jurassic Xinhe Formation upper section in Yabrai Basin,its thermal evolutions is in immature stage,so they are not source rock.While the lower Xinhe has rich abundance and good type of organic matter and thermal evolution is in mature stage,it is the main source rock.The organic matter abundance is rich and the type is poor about Qingtujing Formation,it is the subordinate source rocks.This paper ensures that the TOC lower limit of Yanchang sub-sag is 1.0% and of Xiaohu sub-sag is 0.7%,while Suotuo sub-sag is of no expulsion potential.The effective source rocks mainly distribute in Yanchang sub-sag and Xiaohu sub-sag,the thickness is up to about 600 m in the center of Xiaohu sub-sag,there is no effective source rock in Suotuo sub-sag.The matching relation of the hydrocarbon generation stage and petroleum forming period is good,the present petroleum distribute in the area of effective source rock with high thickness,meaning that the effective source rock has a great role in controlling the petroleum generation and distribution.Petroleum in Xiaohu sub-sag is mainly from source rock of different maturities in the lower Xinhe Formation,most sand bodies are thin sand layers lie in source rocks,it is a typical self-source and self-reservoir pool formation.