抄録
The Da’anzhai Member of the Jurassic in the Sichuan Basin is an important potential area for lacustrine shale gas resources in China, with significant exploration and development prospects. Based on systematic sampling and testing, this study comprehensively analyzed the lithofacies characteristics, organic matter properties, physical parameters, and formation conditions of the shale in this member. It investigated the main controlling factors of shale gas enrichment. The results show that the Da’anzhai Member shales exhibit significant heterogeneity, with TOC content ranging from 0.1% to 3.9%, primarily consisting of Type Ⅱ2 and Type Ⅲ organic matter. The Ro values range from 1.1% to 1.8%, indicating that the shale is mature to highly mature. Porosity ranges from 0.9% to 8.4%, dominated by micropores and mesopores, and the average gas content reaches 0.9 m³/t, demonstrating good reservoir performance. Shale gas enrichment is primarily controlled by a combination of a semi-deep lacustrine depositional environment, favorable lithofacies assemblages, well-developed natural fractures, and effective preservation conditions. Based on this research, evaluation criteria for favorable shale gas zones were established, and five high-quality exploration areas were identified, including the southwestern Yuanba, southeastern Langzhong, Yilong, northwestern Fuling, and northwestern Jiannan regions. This study elucidates the formation mechanism and enrichment patterns of shale gas in the Da’anzhai Member of the Jurassic in the Sichuan Basin, providing scientific evidence and technical support for the efficient exploration and development of lacustrine shale gas resources.
