鄂尔多斯盆地甘泉西部延长组下组合烃源岩生物标记化合物特征研究OACHSSCD

To clarify the geological genesis and evolution characteristics of the Lower Member of the Yanchang Formation source rocks in the western part of Ganquan,Ordos Basin,this paper,based on the tectonic background of the southern part of the northern slope of Shaanxi Province,combined with the Triassic late lake basin expansion and regression sedimentary sequence,systematically analyzed the distribution characteristics of biomarker compounds such as n-alkanes,terpenoids,and steranes through techniques such as gas chromatography-mass spectrometry kerogen microscopy and elemental analysis.The study also correlated the sedimentary facies evolution,source supply,and regional hydrocarbon accumulation patterns,revealing the geological significance of the source rocks interms of organic matter sources,sedimentary environments,and thermal evolution,and established the"source-reservoir-cap"hydrocarbon accumulation configuration relationship.The results show that the organic matter type of the source rocks in the study area is Type Ⅰ and Type Ⅱ1,with high organic carbon content(TOC),reaching the standard of high-quality source rocks;the Pr/Ph ratio(0.59～1.43),V/(V+Ni)ratio(average 0.78),and horizontal bedding sedimentary structures jointly indicate a weakly reducing-weakly oxidizing,deep lake-semi-deep lake sedimentary environment,and the reduction degree is the highest in the Chang 73 sub-member(the maximum lake transgression period);the organic matter sources have mixed characteristics:mainly low-grade planktonic organisms,and partly from higher organisms;the source rocks have generally entered the mature stage(Ro=0.87％～1.26％),at the peak of hydrocarbon accumulation,and form a"self-generation-self-storage-upper generation-lower storage"hydrocarbon accumulation model with the Chang 8～Chang 9 tight sandstone reservoirs,and lithologic traps and fracture development areas are favorable exploration directions.