The resource potential of the Xujiahe Formation in the Sichuan Basin is widely recognized, yet the complexity of its gas-water distribution poses significant constraints on subsequent exploration and development. Through the application of experimental techniques including casting thin section analysis, high-pressure mercury injection, and formation water ion analysis, a systematic investigation was conducted into the fundamental geological characteristics, gas-water distribution patterns, and key controlling factors of tight sandstone gas reservoirs within the third member of the Xujiahe Formation in northwestern Sichuan. It is demonstrated that these reservoirs are characterized by low porosity and low permeability, dominated by fine pore throats. Three principal types of source-reservoir configurations are identified: self-sourcing and self-reservoiring, laterally-sourced and laterally-reservoired, and lower-sourced and upper-reservoired. Among these, the self-sourced and self-reservoired type exhibits the closest contact and the highest gas content. The gas-water distribution is marked by the cross-distribution of high- and low-production wells in the planar view and a distinct “gas above, water below” trend vertically, with overall complex gas-water relationships significantly influenced by faulting. The early paleo-structural slope in northwestern Sichuan is interpreted to have provided favorable conditions for natural gas accumulation, with subsequent reservoir densification contributing to effective preservation following structural inversion. Multiphasic tectonic activity has resulted in the development of a conjugate fault system, primarily oriented northwest and near east-west, wherein fault hierarchy controls productivity variations: fourth-order fault zones are associated with high gas production, whereas first- and second-order fault areas are prone to water production. Fracture development locally enhances reservoir seepage capacity, and high-quality reservoirs with porosity exceeding 6% are identified as favorable intervals for natural gas enrichment. The gas-water enrichment is governed jointly by early fault conduits and late-stage reservoir densification, with the quality of source-reservoir configuration determining variations in natural gas charging intensity and gas-water distribution. The gas-water distribution exhibits pronounced heterogeneity, described as “cross-distributed horizontally and gas-over-water vertically,” with particularly complex gas-water relationships observed in fault-developed areas.