Abstract: The Xujiahe Formation in Sichuan Basin possesses abundant tight sandstone gas resources, which has long been a key target for increasing reserve and production. However, the hydrocarbon exploration and development efficiency has been low due to the factors including tight reservoir, complex gas-water interactions, unclear accumulation mode, great difficulties in reservoir and fracture prediction, and poor applicability of reservoir fracturing stimulation technologies. In recent years, efforts have been made to achieve a breakthrough in integration project of geology, geophysical prospecting and engineering, by which Hexingchang gas field, a deep tight sandstone gas field in the Member 2 of Xujiahe Formation, has been successfully established. This achievement has contributed to the newly-proven geological natural gas reserves of 1 330.12×10⁸m³, and the annual natural gas production of more than 10×10⁸m³. The results show as follows. (1) There are several sets of high-quality source rocks such as Xiaotangzi Formation and Member 2 of Xujiahe Formation in Hexingchang gas field, featuring vertically superimposed development and extensive lateral distribution, which in combination with thick-bedded high-energy channel tight sandstone reservoirs form a good source-reservoir assemblage. (2) Multi-type large-scale transportation systems provide large storage space and highly efficient migration pathway for natural gas. (3) The Hexingchang gas field demonstrates the hydrocarbon accumulation and enrichment mode featuring multi-stage oil-gas charging, massive gas-bearing reservoirs, and efficient enrichment through large-scale migration system. The coupling between hydrocarbon generation and reservoir formation are decisive factors for the dynamic accumulation process characterized with early-stage large-scale charging of medium-low maturity hydrocarbons, mid-stage low efficient diffusive charging of high-maturity natural gas, and late-stage efficient migration and accumulation through migration systems. The spatiotemporal coupling relationships among source rocks, reservoirs, and migration systems play a key role in controlling the large-scale hydrocarbon accumulation and enrichment. Meanwhile, on the basis of the pre-stack stochastic inversion reservoir prediction technology via frequency-division reconstruction and the fine fracture characterization technology via multi-attribute fusion, a suit of differentiated development technologies tailored to diverse-scale migration systems and volume fracturing technologies of complex fracture networks have been established, which help achieve the efficient exploration and development of deep ultra-low permeability tight sandstone gas reservoirs in Xujiahe Formation of the western depression of Sichuan Basin. Moreover, these integrated technologies have promoted technological innovation in related fields, providing experience and reference for the exploration and development of similar gas reservoirs at home and abroad.

Key words: Member 2 of Xujiahe Formation, geological conditions for accumulation, key technologies for exploration and development, Hexingchang gas field, Sichuan Basin

摘要： 四川盆地须家河组致密砂岩气资源丰富,一直是增储上产的重点目标,但受制于储层致密、气水关系复杂、成藏模式不清、储层及裂缝预测难度大以及压裂改造技术适应性差等因素,长期以来的勘探开发效果较差。近年来,通过“地质—物探—工程一体化”持续攻关,川西坳陷建成了须家河组二段(须二段)深层致密砂岩气田——合兴场气田,新增天然气探明地质储量1 330.12×10¹²m³,天然气产量超过10×10⁸m³/a。研究结果表明:合兴场气田的小塘子组与须二段多套优质烃源岩在纵向上呈叠置发育,平面上广泛分布,与厚层高能河道致密砂岩储层形成了良好的源-储配置;多类型规模输导体的发育为天然气提供了大规模的储集空间和高效运移通道;合兴场气田具有“多期油气充注、规模储层整体含气、规模输导体高效富集”的成藏富集特征。成烃-成储的耦合特征决定了合兴场气田具有早期中—低成熟油气规模充注、中期高成熟天然气低效扩散充注、晚期天然气输导体高效运聚的动态成藏过程。烃源岩-储层-输导体的时空耦合关系是油气规模富集成藏的关键控制因素。同时,基于分频重构叠前随机反演的储层预测技术和多属性融合的裂缝精细刻画技术,形成了针对不同规模输导体类型的差异化开发技术和复杂缝网体积压裂技术,实现了川西坳陷须家河组深层特低渗致密砂岩气藏的高效开发,并推动了相关领域方法的技术创新,为国内外同类型气藏的勘探开发提供了经验借鉴。

关键词: 须家河组二段, 成藏地质条件, 勘探开发关键技术, 合兴场气田, 四川盆地