Pore-scale modeling of gas–water two-phase flow in porous gas reservoirs

Porous gas reservoirs are abundant in reserves and represent a significant proportion of discovered gas reservoirs worldwide. During the middle to late stages of development, these reservoirs often face the risk of water invasion, which reduces displacement efficiency and gas recovery rates. However, the gas-water two-phase flow behavior in porous media remains a persistent challenge. To address this issue, a pore-scale gas–water two-phase flow model was established by coupling fluid flow equations with two-phase interfacial transport equations. Using micro-computed tomography technology, a digital core model representative of a porous gas reservoir was reconstructed. The gas–water distribution and migration characteristics were simulated during both the gas-driven water accumulation stage and the water-invasion depletion extraction stage. The effects of injection rate, wettability (contact angle), and interfacial tension on flow behavior and displacement efficiency were analyzed. The results show that wettability governs the two-phase distribution: while water displaces gas along pore walls under hydrophilic conditions, it occupies pore centers under hydrophobic conditions, thereby increasing flow resistance. Increasing the injection rate significantly enhances the driving force and substantially improves gas recovery. In contrast, higher interfacial tension strengthens capillary forces, leading to greater gas retention and reduced ultimate recovery. These results provide an important theoretical foundation and key technical support for understanding gas-water seepage mechanisms in porous gas reservoirs, predicting development dynamics, and formulating rational development strategies.