Abstract: Initial hydrocarbon exploration in Feixianguan Formation of Sichuan Basin primarily focused on high-energy oolitic shoals along the platform margin with structural stability. Exploration in complex structural belt, such as the Longmen Mountain frontal belt, faces high risks and limited attention, largely owing to poorly defined reservoir properties and accumulation patterns. On July 25, 2025, Well Jitan1, deployed in the intra-platform shoal development zone of Shuangyushi area, achieved a high-yield industrial gas flow of 166.68×10⁴m³/d from the Member 2 of Feixianguan Formation, marking a significant breakthrough in this field. Based on the integrated analyses of rock thin sections, well logs, seismic interpretations, and organic geochemical data, the following understandings have been obtained. (1) In Shuangyushi area, intra-platform oolitic shoals were developed in the Member 2 of Feixianguan Formation. The thinning zone in the Member 3 of Feixianguan Formation can effectively indicate the paleogeographic high positions of depositional period and shoal bodies in the Member 2 of Feixianguan Formation. (2) The reservoir rocks in the Member 2 of Feixianguan Formation are mainly composed of weakly- and non-dolomitized oolitic limestones with well-developed inter- and intra-granular dissolution pores and micro-fractures, forming high-quality fracture-pore type reservoirs connected across fault zones. (3) The Member 2 of Feixianguan Formatoin at Well Jitan1 is characterized by joint supplies of hydrocarbons from Lower Cambrian and Upper Permian source rocks, efficient hydrocarbon migration and accumulation channels from multiple sets of parallel reverse faults together with thick and continuous reservoir rocks, and high-quality cap rocks from the overlying thick gypsum rocks within the Member 4 of Feixianguan Formation and the Leikoupo Formation. This configuration establishes a favorable source-reservoir-cap assemblage and develops structural-lithologic traps. (4) A hydrocarbon accumulation model featuring multi-source hydrocarbon supply, fault and intra-platform shoal connectivity, and hydrocarbon entrapment in structural-lithologic trap was established for the Member 2 of Feixianguan Formation in Shuangyushi area. The exploration breakthrough of Well Jitan1 confirms that the superimposed area between the structural highlands or strongly modified areas and high-energy reef-shoals is conducive to the formation of high-quality reservoirs, highlighting the critical role of fracture communication, and indicating the enormous exploration potential. This study aims to provide a reference for hydrocarbon exploration in the superimposed areas between the structural highlands or strongly modified areas and high-energy reef-shoals in Sichuan Basin and other basins.

Key words: gas exploration breakthrough, complex structural zone, hydrocarbon accumulation condition, intra-platform shoals, Feixianguan Formation, northwestern Sichuan Basin

摘要： 四川盆地飞仙关组前期勘探主要聚焦构造相对稳定的高能台缘带，而龙门山前带等复杂构造区因储层与成藏规律认识不清，勘探风险大，关注有限。2025年7月25日，部署于双鱼石地区台内滩发育区的集探1井在飞仙关组二段（飞二段）获产气量为166.68×10⁴m³/d的高产工业气流，实现了该领域的重大突破。基于岩屑薄片、测井、地震和有机地球化学资料综合分析，取得以下认识：①双鱼石地区飞二段发育台内鲕粒滩，飞仙关组三段厚度减薄区可有效指示飞二段沉积期古地貌高部位及滩体分布；②飞二段储集岩以弱白云石化—未白云石化鲕粒灰岩为主，发育粒间/粒内溶孔及微裂缝，形成跨断裂连片分布的优质裂缝-孔隙型储层；③集探1井飞二段表现为下寒武统与上二叠统烃源岩联合供烃，多排平行逆断层与厚且连片的储层构成高效运聚通道，上覆飞仙关组四段—雷口坡组巨厚膏岩提供优质封盖，由此形成了良好的生-储-盖配置与构造-岩性圈闭；④双鱼石地区飞二段具有“多源供烃、断裂-台内滩连通、构造-岩性圈闭聚烃”的成藏模式。集探1井的勘探突破证实构造高部位/强烈改造区与高能礁滩叠合区有利于优质储层形成，凸显了裂缝沟通的关键作用，预示着叠合区具有巨大的勘探前景。该研究以期为四川盆地乃至其他盆地构造高部位/强烈改造区与高能礁滩叠合区的油气勘探提供借鉴。

关键词: 天然气勘探突破, 复杂构造带, 成藏条件, 台内滩, 飞仙关组, 川西北地区