Geochemical Characteristics and Oil Generation Potential Evaluation of Lower Cretaceous Xiahuapidianzi Formation Shale in the Southeastern Sankeyushu Depression, Tonghua Basin: Evidence from Shale Pyrolysis Experiments and Biomarkers

Oil and gas exploration in the Tonghua Basin, a potential petroleum-bearing basin in Northeast China, is still in the early stages. In this article, the organic geochemistry and kerogen petrology of a Xiahuapidianzi formation shale core from a geological survey well in the southeastern Sankeyushu depression of the tonghua basin are studied. The mean vitrinite reflectance (Ro) values (0.85-2.36%), pyrolysis T-max values (438-485 degrees C), and biomarker parameters of the studied samples indicate that the Xiahuapidianzi formation shale have entered the oil generation window and that its maturity may be at its peak. The depositional environment of the Xiahuapidianzi formation featured high-salinity reducing conditions, and the source material was mainly plankton and higher plants but may have also included some marine biological components. Volcanic activities and sea water were conducive to the accumulation of organic matter because they brought nutrients to the organic organisms in the lake basin, increased the productivity of organic matter, and led to the formation of a reduction environment conducive to the preservation of organic matter at the bottom of the lake. According to the analysis of the geochemical data, the Xiahuapidianzi formation shale can be divided into six units. The first, third, and fifth units have good to very good source rocks and good shale oil production potential, and these units may be important contributors to the southeastern oilfield of the Sankeyushu depression in the Tonghua Basin.