Oil-bearing characteristics and exploration significance of inter-salt shale in Qianjiang formation, Qianjiang depression, Jianghan basin

In order to study the oil content and exploration potential of inter-salt shale in different structural positions in Qianjiang depression, Jianghan basin, the cores from the 10th rhythmic of the Eq3 member of Qianjiang formation of well W99 and adjacent wells were taken as the main research objects. The oil-bearing characteristics of inter-salt shale from the uplift area and depression area were analyzed by the Rock-Eval 6 with both conventional pyrolysis heating program and the multi-stage temperature pyrolysis analysis heating program. The results show that the inter-salt shale from the uplift area has excellent oil content due to the contribution of migrated shale oil from the depression area. The total organic carbon (TOC) values of 35 samples from the uplift area are between 0.60% and 6.38%, with an average of 3.39%. The S1 values of rock pyrolysis are between 2.73 and 28.47 mg/g, with an average of 14.14 mg/g. The oil saturation index (OSI) values are between 225 and 564 mg/g and generally greater than 100 mg/g, with an average of 405 mg/g. And the realistic movable oil S1-1 values are between 0.75 and 5.89 mg/g, with an average of 3.26 mg/g. Although these indexes meet the high-quality source rock standard, the maturity of shale in the uplift area is low. The main reason for good oil content is the lateral migration of mature to high mature shale oil from the depression area. Therefore, it is considered that there should be in-situ shale oil enrichment in the depression area, and more attention should be paid to the future exploration and deployment. © 2019, Editorial Board of Journal of CUMT. All right reserved.