The Generation And Expulsion Characteristics Of Hydrocarbon And The Resource Potential Of Es₃ Source Rocks In Nanpu Sag

The third member of the Shahejie Formation?Es₃?is the main source rock of Nanpu sag.Besides the geological and geochemical characteristics of Es₃,this paper also analyzes generation and expulsion mode of hydrocarbon.And then,the oil and gas resource potential and distribution are evaluated.Firstly,the organic matter abundance of source rock samples in different lithofacies indicate that the main source rocks include shales and dark?black,dark gray,gray and brown?mudstones.The geochemical parameters show that the source rocks of Es₃ have high abundance of organic matter and medium hydrocarbon generation potential.The kerogen is type III and type II₂,and in mature-highly mature stage.Secondly,according to the hydrocarbon expulsion threshold and expulsion plate,the effective source rocks of Es₃ are identified.The deposition center of effective source rocks is located in Gaoshangpu,Beipu and Laoyemiao structures with a maximum thickness of 700m.Thirdly,the generation and expulsion mode of hydrocarbon,built by hydrocarbon generation potential method,indicates that the hydrocarbon expulsion threshold R_o is 0.84%,the hydrocarbon expulsion peak R_o is 1.05%,and the hydrocarbon expulsion efficiency is up to 82%.The Gaoshangpu structure and the Beipu-Laoyemiao structural belt are the main hydrocarbon-generating centers.The Beipu-Laoyemiao structural belt is a hydrocarbon expulsion center,and the Gaoliu area has higher residual hydrocarbon intensity than other areas.Furthermore,the cumulative quantity of generated and expulsive and residual hydrocarbon of Es₃ is 111.6×10⁸t,40.09×10⁸t,and 71.51×10⁸t respectively.The unconventional oil and gas resource of the I system is most abundant,and the tight hydrocarbon resource and shale oil resource is 9.61×10⁸t and 8.52×10⁸t respectively.