Abstract: After more than ten years of exploration and practice, a series of progress has been made in marine shale gas exploration in Sichuan Basin. During that period, focusing on Wufeng-Longmaxi formations as the most favorable pay zone, a few theories for the enrichment and high production of shale gas were proposed, the exploration and development technologies integrating geological evaluation, development optimization, optimal-fast drilling, volume fracturing, factory operation and clean exploitation was formed, and a large shale gas field with reserves of one trillion cubic meters was proved. At an important time for the development of shale gas exploration in China, it is of great significance to promote the exploration and development of marine shale gas by reviewing the exploration and development history of marine shale gas, summarizing the achievements and knowledge of shale gas in Wufeng-Longmaxi formations in terms of geological conditions and enrichment laws, and making an outlook on the key replacement fields for marine shale gas exploration in Sichuan Basin. (1) The exploration and development of marine shale gas in Sichuan Basin have gone through four stages:layer and zone evaluation stage to find the target; pilot test stage of shallow to medium-deep reservoir; demonstration zone construction stage of shallow to medium-deep reservoir; stage of shallow to medium-deep reservoir production, deep reservoir evaluation, non-pressurized shale gas evaluation, three-dimensional development evaluation, ultra-deep and new reservoir exploration. (2) The sedimentary conditions of the Wufeng-Longmaxi formations in Sichuan Basin are superior, in which the deepwater shelf shales with high organic content are continuously and stably distributed. Shale gas mainly occurs in organic matter pores, and its reservoirs are concentrated longitudinally with large continuous thickness. The structures are relatively simple in the southern Sichuan Basin and the Fuling block of southeastern Sichuan Basin. The conditions for shale gas enrichment and preservation include sustained gas supply and reservoirs far away from the ancient/present denudation areas and oil-gas escape areas in large faults. At present, the shale gas resources in Wufeng-Longmaxi formations are 33 19×10¹²m³ with a proved rate of 9.4%, showing great exploration potential. (3) There are rich marine shale gas resources in Sichuan Basin. In addition to Wufeng-Longmaxi formations, there are several sets of marine shale gas reservoirs as reserves in the horizons shallower than 4 500 m. The Cambrian Qiongzhusi Formation, Permian Wujiaming Formation and Dalong Formation as the strategic breakthrough strata, the favorable shale gas reservoirs mainly lie in Weiyuan-Ziyang area inside and around aulacogen for Qiongzhusi Formation, with the predicted resource potential of 1.40×10¹²m³, and in Jiange-Nanjiang area and Dazhu-Kaijiang area of northern Sichuan Basin, and Lichuan area of southeastern margin of Sichuan Basin for Wujiaping Formation and Dalong Formation, with the predicted resource potential of 0.91×10¹² m³. The Member 1 of Xujiahe Formation as the strategic preparation layer, its favorable shale gas reservoirs mainly lie in Ya'an-Qionglai area, with the predicted resource potential of 0.88×10¹² m³.

Key words: Sichuan Basin, Wufeng Formation-Longmaxi Formation, Qiongzhusi Formation, Wujiaping Formation, Dalong Formation, Member 1 of Xujiahe Formation, marine shale, favorable area for shale gas exploration and development

摘要： 历经十余年探索实践，四川盆地海相页岩气勘探取得了一系列进展，锁定五峰组—龙马溪组为最有利产层，提出了一批页岩气富集高产理论，形成了集地质评价、开发优化、优快钻井、体积压裂、工厂化作业、清洁开发等为一体的勘探开发技术，探明了万亿立方米级储量的页岩气大气田。时值中国页岩气勘探发展的重要节点，回顾四川盆地海相页岩气勘探开发历程、梳理五峰组—龙马溪组页岩气在地质条件与富集规律上的成果认识、展望四川盆地海相页岩气勘探的重点接替领域，对推进盆地海相页岩气的勘探开发有积极意义。①四川盆地海相页岩气勘探开发经历了4个阶段：评层选区找目标阶段；浅层至中—深层先导试验阶段；浅层至中—深层示范区建设阶段；浅层至中—深层上产、深层评价、常压页岩气评价、立体开发评价、超深层和新层系探索阶段。②四川盆地五峰组—龙马溪组的沉积条件优越，深水陆棚相高有机质含量页岩呈连续稳定分布；页岩气主要赋存在有机孔隙中，页岩储层在纵向上集中发育，连续厚度大；川南地区和川东南涪陵区块的构造相对简单，气源持续补给、远离古/今剥蚀区和大型断裂逸散区是页岩气富集保存的有利区；目前，五峰组—龙马溪组的页岩气资源量为33.19×10¹²m³，探明率为9.4%，勘探潜力巨大。③四川盆地海相页岩气资源丰富，除五峰组—龙马溪组外，4 500 m以浅还存在多套海相页岩气后备勘探层系；寒武系筇竹寺组、二叠系吴家坪组和大隆组为战略突破层系，其中，筇竹寺组页岩气有利区主要分布在裂陷槽内和槽缘的威远—资阳一带，预测资源潜力达1.40×10¹²m³，吴家坪组和大隆组页岩气有利区主要分布在川北剑阁—南江一带、大竹—开江一带和盆地东南缘的利川地区，预测资源潜力达0.91×10¹²m³；须家河组一段为战略准备层系，页岩气有利区主要分布在雅安—邛崃一带，预测资源潜力达0.88×10¹²m³。

关键词: 四川盆地, 五峰组—龙马溪组, 筇竹寺组, 吴家坪组, 大隆组, 须家河组一段, 海相页岩, 页岩气勘探开发有利区