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Advancements in evaluation and development technologies have established continental shale oil and gas as vital future alternative energy sources for China. Recently, exploratory wells drilled in the Lianggaoshan Formation shale segment of the Middle Jurassic in the Qijiang area, southeastern Sichuan, have shown promising oil and gas indications. To clarify the basic geological characteristics of shale oil and gas in this area, the organic-rich shale of the Lianggaoshan Formation in the southeastern Qijiang area was chosen as the subject of study. Based on core observations and laboratory analyses, an evaluation of the basic geological conditions for shale oil and gas in the second section of the Lianggaoshan Formation in the Qijiang area was conducted. This was combined with high-quality shale seismic prediction and structural preservation condition assessments to identify exploration potential and direct future exploration efforts. Using typical wells in the Qijiang area as case studies, resource potential analysis was performed by integrating organic geochemical characteristics, thermal maturity, reservoir physical properties, and oil and gas bearing characteristics. Results indicate that the high-quality shale in the lower subsection of the second member of the Lianggaoshan Formation spans an extensive area of 4 569 km2, with thickness ranging from 20 to 39 m. Controlled by semi-deep lacustrine facies, this shale exhibits an average organic carbon content of 1.3% to 1.6%, with organic matter types predominantly Ⅱ1 to Ⅱ2, and vitrinite reflectance values between 1.00% and 1.29%. These characteristics suggest significant hydrocarbon generation potential and promising measured oil and gas content. The high-quality shale is characterized by high gamma-ray (GR) readings, high acoustic time difference, and low density. Seismic waveform classification and acoustic impedance inversion techniques identified the Dingshan, Dongxi, and Guanshengchang areas as regions of concentrated shale thickness. These areas feature large, broad, and gentle synclines with favorable drilling results, indicating good overall preservation conditions. The main burial depths ranges from 1 000 to 3 500 m, with uniform structural stress and good compressibility. In summary, the analysis indicates that the continental shale in the Lianggaoshan Formation of the Qijiang area possesses favorable preservation conditions and substantial shale oil resources exceeding 500×106 t, offering significant exploration potential. This evaluation provides a strategic framework for expanding exploration efforts in continental shale oil and gas within the Sichuan Basin.

The Fuxing area of the Sichuan Basin is known for its multiple sets of organic-rich shale in the Jurassic period, with several wells yielding significant amounts of industrial oil and gas. Understanding the characteristics and factors influencing the enrichment of different shale facies sedimentary reservoirs is crucial for effective exploration. Through detailed rock core descriptions, experimental analysis, and drilling exploration, the author has classified and compared fine-grained sedimentary rock facies in terrestrial strata, characterized reservoirs, identified types of oil and gas reservoirs, and analyzed the main factors influencing enrichment and productivity. The study reveals that the Jurassic strata in the Fuxing area contain two sets of high-quality shale with semi-deep lacustrine facies: the first sub-section of the Dongyuemiao section of the Ziliujing Formation and the lower sub-section of the second section of the Lianggaoshan Formation. These shale layers exhibit multi-layer stacking, moderate TOC content, well-developed bedding, integrated source storage, and high gas/oil ratio characteristics. The lithology of these target shale layers is complex, leading to the establishment of a four-element lithofacies classification scheme based on "color-TOC-sedimentary structure-mineral composition". This scheme identifies the gray-black high carbon sand-laminated clay shale as the favorable lithofacies for the lower sub-section of the second section of the Lianggaoshan Formation, and the gray-black high carbon medium debris-laminated and fine sand medium debris-laminated clay shale as the favorable lithofacies for the eastern sub-section. The three lithofacies in the study area are horizontally distributed in a stable manner. The gray-black high carbon fine sand layer, medium debris layer, and fine sand-medium debris layer type clay shale exhibit reservoir characteristics of "porous coexistence, large pores and throats, and integrated pores and fractures". These reservoir properties, including good permeability, facilitate the efficient storage and flow of shale oil and gas in the pore-fracture storage system. The first sub-section of the Dongyuemiao section is a condensate gas reservoir, while the lower sub-section of the Lianggaoshan Formation's second section is a volatile oil reservoir. Key factors contributing to the enrichment of continental shale oil and gas have been identified, including medium to high hydrocarbon generation potential and strong retention rates supporting the accumulation of laminated shale oil and gas. A favorable hydrocarbon-diagenesis-reservoir formation configuration promotes oil and gas accumulation. Additionally, the development of micro cracks and suitable thermal evolution aids in hydrocarbon enrichment and flow, while large, wide, gentle synclines and high-pressure overpressure conditions support the sustained preservation of hydrocarbons.