Abstract: With the continuous advancement of hydrocarbon exploration in petroliferous basins across China, expanding strategic replacement areas has become a critical issue for oil and gas development. Recent exploration breakthroughs reveal that in-situ tight gas within source rocks of the Sichuan Basin possesses resource potential exceeding 1×10¹² m³, emerging as a prospective new strategic replacement area. Detailed core descriptions, well log interpretations, and geochemical data analyses are integrated in this study to investigate the genetic types and stratigraphic distribution characteristics of in-situ tight gas in the Sichuan Basin, elucidate its hydrocarbon accumulation patterns, and clarifie resource potential with future exploration directions. Key findings include:① Influenced by multicyclic tectonic evolution and frequent sea-lake level fluctuations, the Sichuan Basin has developed multiple sets of high-quality thick source rocks, forming both marine and terrestrial in-situ tight gas systems.② Two distinct source-reservoir configurations are identified: a) Near-source accumulation enveloped by source rocks with superior sealing conditions (e.g., Qiongzhusi Formation tight gas and Xu5 member tight gas); b) Integrated source-reservoir systems with overpressure preservation (e.g., tight gas in the Lei-32 submember and Mao-1 Member marine marl). ③ Three in-situ tight gas systems demonstrate combined resource potential exceeding 1×10¹² m³: (1) Qiongzhusi Formation tight sandstones (most favorable area: Ziyang-Penglai region); (2)Leikoupo Formation marine marls (primary prospective area: southern-central Sichuan); (3)Xu5 member tight sandstones (key exploration target: Penglai-Jinhua area). These systems represent crucial future exploration frontiers, with particular emphasis on the Ziyang-Penglai region for Qiongzhusi tight gas development.

Key words: Sichuan basin, In-situ tight gas, Qiongzhusi formation, Mao1 member formation, Xu5 member, Resource potential