Abstract: The Da’anzhai member of the Lower Jurassic Ziliujing formation is the most favorable layer for the development of continental shale oil in the Sichuan basin, with immense potential for shale oil exploration. However, systematic research on the thermal evolution history of this formation remains scarce. Using a petroliferous basin simulation system, this study comparatively analyzes the differences in thermal evolution and hydrocarbon generation of the shale in Da’anzhai member between the northern and central parts of the Sichuan basin and discusses their impacts on shale oil enrichment. The thermal evolution degree of the Da’anzhai shales in the study area increases gradually from southwest to northeast, with the shales categorized into a highly matured zone and a matured zone. The highly matured zone, located in the northern part of the study area, exhibits vitrinite reflectance values ranging from 1.3% to 1.7%, primarily developing Type III organic matter. Hydrocarbon generation began in the early Late Jurassic, peaked at the end of the Late Jurassic, and experienced two phases of hydrocarbon generation. The matured zone, located in the central to southern parts of the study area, shows vitrinite reflectance values ranging from 0.9% to 1.3%, primarily developing Type II1 to II2 organic matter. With relatively smaller Jurassic sedimentary thickness, organic matter in this region matured later, entering early oil generation by the Late Jurassic and peaking in hydrocarbon generation during the Early Cretaceous, with only one phase of hydrocarbon generation. Compared to the northern region, the central region contains large deposits of organic-rich shales, forming a robust foundation for Da’anzhai shale oil. However, tectonic uplift and stratum erosion since the Paleogene have somewhat impaired oil and gas preservation in this region.

Key words: Sichuan basin, Lower Jurassic, Ziliujing formation, Da’anzhai member, thermal evolution history, hydrocarbon generation capacity, preservation, shale oil and gas