Abstract: Large tight sandstone gas reservoirs in Tianfu gas field of Sichuan Basin were discovered in the Member 2 of Shaximiao Formation in 2019 and the Member 1 of Shaximiao Formation in 2021, respectively. The proven reserves are 1 349×10⁸m³ and the production is 15.7×10⁸m³ in 2022. Based on the core and geochemical analysis data, the paper investigates the sedimentary reservoir characteristics, natural gas geochemical characteristics, gas reservoir types and gas reservoir formation conditions of Shaximiao Formation in Tianfu gas field. In the study area, shallow-water deltaic and lacustrine deposits are found in the Member 1 of Shaximiao Formation, while fluvial deposits are found in the Member 2 of Shaximiao Formation. The lithologies of the reservoir are mainly composed of feldspathic litharenite and lithic arkose, and the reservoir spaces are mainly occupied by residual intergranular pores, followed by feldspar dissolution pores. The natural gas source of reservoir is mainly from the Triassic Xujiahe Formation. The natural gas in the Member 1 of Shaximiao Formation and the 6th, 8th and 9th sand groups of 1st submember of Member 2 of Shaximiao Formation is dominated by coal-type gas with a small amount of mixed gas, while the gas in the 7th sand group of 1st submember of Member 2 of Shaximiao Formation is characterized by the occurrence of both mixed gas and oil-type gas. The gas reservoir in Shaximiao Formation of Tianfu gas field is a large lithologic gas reservoir with accumulation regularity of dual-source and multi-phase charging, fault and sandbody transport, accumulation around the source, and differential enrichment at the channel. A series of key exploration and development technologies have been developed by tackling the key exploitation problems of large tight sandstone gas reservoirs in Shaximiao Formation of Tianfu gas field, i.e., (1) technology of precisely choosing layers under the constraint of high-precision isochronous stratigraphic framework, (2) technology of finely characterizing sand bodies and precisely predicting target based on 3D seismic survey, (3) supporting technology to accelerate exploration and production based on horizontal well and volume fracturing, (4) processing technology of exploitation and transportation on the ground for the purpose of fast construction, investment, optimization and simplification, (5) integrated technical and economic template for scale and cost-effective development. The discovery of Tianfu gas field has improved the exploration and development of tight sandstone gas in China, and enriched the exploration methods of tight sandstone gas, and effectively promoted the exploration and development process of tight sandstone gas in Sichuan Basin.

Key words: Sichuan Basin, Shaximiao Formation, tight sandstone, accumulation condition, exploration and development technology

摘要： 四川盆地天府气田于2019年和2021年分别在沙溪庙组二段（沙二段）和沙溪庙组一段（沙一段）发现大型致密砂岩气藏；2022年，气藏探明储量为1 349×10⁸m³，产量为15.7×10⁸m³。基于岩心和地球化学分析等资料，对天府气田沙溪庙组的沉积储层特征、天然气地球化学特征、气藏类型及气藏形成条件开展了研究。研究结果认为：天府气田沙一段为浅水三角洲—湖泊相沉积，沙二段为河流相沉积；储层的岩性以长石岩屑砂岩和岩屑长石砂岩为主，储集空间主要为残余粒间孔，其次为长石溶孔；天然气的气源主要来自三叠系须家河组；沙一段和沙二段1亚段6砂组、8砂组、9砂组的天然气以煤型气为主，少量为混合气，而沙二段1亚段7砂组具有混合气和油型气的特征；天府气田沙溪庙组气藏整体为大型岩性气藏，具有"双源多期充注、断砂复合输导、环源规模聚集、河道差异富集"的成藏规律。通过研究天府气田沙溪庙组大型致密砂岩气藏，配套形成了一系列勘探开发关键技术：①高精度等时地层格架约束下的精准选层技术；②以三维地震为核心的砂体精细刻画及靶体精准预测技术；③以水平井＋体积压裂为核心的提速提产配套技术；④以快建快投、优化简化为目的的地面配套集输处理；⑤以规模效益开发为核心的一体化技术经济模板。天府气田的发现提升了中国致密砂岩气的勘探开发水平，丰富了致密砂岩气的勘探方法，有效推动了四川盆地致密砂岩气的勘探开发进程。

关键词: 四川盆地, 沙溪庙组, 致密砂岩, 成藏条件, 勘探开发技术