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

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