The Evaluation Study Of Source Rocks In The 4^th Submember Of The Third Member Of Shahejie Formation In Shichang Sub-sag Nanpu Depression

Based on a large number of sample data,this paper aims at the geochemical problems in the oil and gas exploration in the Es₃⁴ of Shichang Sub-sag of Nanpu Depression.Based on the multi-discipline theoretical knowledge of oil and gas geochemistry,elemental geochemistry and other experimental analysis techniques,such as rock-eval pyrolysis analysis,saturated hydrocarbon chromatography-mass spectrometry,aromatic hydrocarbon chromatography-mass spectrometry and elemental geochemical analysis,it comprehensively evaluates the organic matter abundance,type and maturity of the source rocks in the study area,and analyzes the factors of the paleoclimate,paleosalinity and REDOX environment of the ancient water body in the formation stage of source rocks,so as to provide a better basis for the oil and gas exploration in the study area.Organic carbon content,the hydrocarbon generation potential,chloroform bitumen"A",pyrolysis parameters and organic carbon isotope and isoprenoid alkanes with parameters such as Pr/n C₁₇and Ph/n C₁₈ value indicates that the source rocks are characterized by high abundance of organic matter with mainly type?and?₁.Biomarker compound parameters indicate that the source rocks of the study area are mainly composed of lower aquatic organisms such as algae and higher terrestrial plants;The sedimentary environment of organic matter is warm and humid paleoclimate,which provides material basis for the formation of high-quality source rocks.The maturity of organic matter in source rocks in the study area is relatively high,and the maturity parameters of Ro and biomarkers indicate that the source rocks in the study area are basically in the maturity stage;The comprehensive analysis of biomarker parameters and trace element parameters shows that the source rocks in the study area are formed in a brackish and weak oxidation-reduction environment.