Abstract: To investigate the transport dynamics of water-driven gas displacement within the intrinsic fracture network of coal, this study extracted the two-dimensional fracture structure of in-situ coal samples using a stereomicroscope. Following binarization, the fracture images were imported into COMSOL software for numerical simulation of water-driven gas displacement. We employed the phase field method to track the water-gas two-phase interface, allowing for a detailed examination of the mechanisms behind trapped gas formation. Additionally, we analyzed the impact of varying fracture densities and apertures on displacement effectiveness. The findings indicate that when the fracture extension direction aligns with the displacement direction, displacement velocity is enhanced, facilitating the formation of preferential flow channels; in narrow throat sections, both velocity and pressure increase. At displacement equilibrium, four types of trapped gas structures—blind-end, "H"-type, variable-diameter, and bypass trapped gas—tend to form, influenced primarily by fracture morphology, capillary forces, and wettability. With fewer fractures, the average water-gas flow rate increases, reducing both average pressure and residual gas content; in contrast, narrower apertures elevate both flow rate and pressure, resulting in higher residual gas levels. This micro-scale study of water-driven gas displacement within real coal fracture networks offers insights for improving gas displacement efficiency at the macro scale.