鄂尔多斯盆地甘泉—富县地区延长组长9—长7段烃源岩地球化学特征及长8致密油源对比OA北大核心CSTPCD

In order to evaluate the quality of the source rocks in the Chang 9-Chang 7 members in the Ganquan-Fuxian area of the Ordos Basin and explore the hydrocarbon sources of the Chang 8 tight oil.The technical methods of TOC,chloroform asphalt"A",rock pyrolysis parameters,specular mass reflectance,organic matter microfraction,biomarker compounds,and monomeric carbon isotopes were used to study the hydrocarbon generation potential,parent material source,and sedimentary environment of the Chang 9-Chang 7 source rocks in this area.Geochemical analysis and oil-source correlation were performed on the Chang 8 crude oil samples.The results show that:(1)Three sets of dark mudstone mainly developed in the study area,specifically the Chang 9,Chang 8,and Chang 7.The organic matter types of the dark mudstone in the Chang 9-Chang 7 are Type Ⅱ1-Ⅱ2;the TOC content ranges from 3.25%to 7.92%,the hydrocarbon generation potential from 3.06 to 38.13 mg/g,and the chloroform asphalt"A"content from 0.18%to 0.69%,identifying them as the best source rocks,all in a high mature evolution stage.(2)The Chang 9-Chang 7 dark mudstone samples formed in a typical freshwater lake environment:the Chang 9 deposits under oxidation-suboxic conditions,the Chang 8 deposits under weak reduction conditions,and the Chang 7 deposits under strong reduction conditions,indicating that the organic matter of the Chang 9-Chang 7 source rocks is derived from a mixed source of lower aquatic organisms and terrestrial higher plants.(3)The Chang 81 and Chang 82 crude oils in the study area belong to the same type.The source rocks of the Chang 9-Chang 7 contribute significantly to the production of the Chang 8 tight oil,with the Chang 7 source rocks being the primary contributors.