Main Controlling Factors of Shale Oil Enrichment in Yanchang Formation of Yan’an Exploration Area

In order to reveal the enrichment characteristics of shale oil in the southeastern Ordos Basin, the shale samples in Yan’an exploration area were taken as the research object, combined with drilling and logging data, geochemical tests such as organic carbon, rock pyrolysis and vitrinite reflectance were carried out, and the shale gas enrichment and main controlling factors of Yanchang Formation in the study area were discussed in detail. The results show that: 1) The organic carbon (TOC) content of the Chang 7 member of the Yanchang Formation is high, the average TOC content is 4.77%, mainly type I and type II kerogen, the maturity of organic matter is low, and the vitrinite reflectance Ro of shale is mainly 0.8% - 1.05%, generating crude oil associated gas and pyrolysis gas. 2) The organic carbon content, pyrolysis parameters free hydrocarbon (S1) and pyrolysis hydrocarbon (S2) are positively correlated with shale oil content, and vitrinite reflectance Ro is positively correlated with shale oil content, indicating that organic matter abundance and thermal evolution maturity directly control shale oil content. 3) There is a positive correlation between lithology, reservoir and oil content. The development degree of shale physical properties has a controlling effect on the oil content of shale. It is concluded that organic matter abundance and maturity are the basic control factors of shale gas occurrence in Yanchang Formation, followed by physical properties.