Study On Shale Oil Resources Potential In Subsection 4 Of The Third Member Of Shahejie Formation In Shichang Sub-Sag Of Nanpu Sag

As a key shale oil exploration area in Jidong Oilfield,the Shichang Sub-sag in Nanpu Sag is a well-developed source rock with large thickness and rich shale oil potential.However,the specific resource needs further analysis and research.Based on the analysis of the hydrocarbon generation characteristics and reservoir performance of the source rocks in the study area,the qualitative interpretation of the shale oil-enriched hydrocarbon generation and storage conditions in the Es₃⁴ was made.The source rocks in the Es₃⁴ have high abundance of organic matter,with TOC distribution ranging from 0.2%to 5.0%,and the average value is 1.48%;kerogen is mainly typeⅠand typeⅡ₁,there are good hydrocarbon generation conditions in the study area;simulated the oil and gas accumulation history of the Es₃⁴ by Basin Mod,clarified the hydrocarbon generation history of the source rocks,and then it can be known that the whole source rocks have entered the mature hydrocarbon generation stage;the microscope shows that its storage space mainly includes intergranular pores,organic matter pores and micro-fractures and so on,the average porosity is 10.88%,the average permeability is 0.13×10^-3μm²,the pores and fractures are developed well and the connectivity is good.Subsequently,through the extraction of chloroform asphalt"A"and pyrolysis experiments to obtain data,quantitative analysis of the residual hydrocarbon mass percentage and the factors of enrichment in the Es₃⁴.Using pyrolysis S₁,its light hydrocarbon recovery coefficient and heavy hydrocarbon compensation coefficient to calculate the mass percentage of residual hydrocarbon is 0.02%～42.53%,the average is about 5.67%,the average mass percentage of residual hydrocarbon in Gaoshangpu area can reach more than 8%.Finally,by further calculating the shale oil resources in the Es₃⁴,the research area was divided according to the resource classification evaluation.The volume of shale oil in the Es₃⁴ is calculated to be 5.03×10⁸ t with small face volume method,which is rich in resources,and further combined with the shale oil mobility index OSI,maturity and pressure coefficient for graded resource evaluation,the study area is divided into"sweet spot","favorable area"and"distant area".Among them,the central area of Gaoshangpu is the"sweet spot"with a resource of 2.05×10⁸ t,the southwestern part of Shichang Sub-sag is the"favorable area"with a resource of 1.23×10⁸ t,and the resource of the"distant area"is 0.94×10⁸ t.Based on geochemical parameters,the saturation adsorption coefficient of the study area was determined to be 0.19,and then calculated movable resource of the Es₃⁴ of Shichang Sub-sag was 1.33×10⁸ t.