Pore-Scale Dynamics of Water Imbibition and Residual-Gas Formation in Tight Gas Reservoir

Forced imbibition of a wetting liquid into a gas-filled tight rock is often expected to advance as a compact front because the liquid-to-gas viscosity ratio is favorable. This expectation can fail when narrow throats, pore-body/throat mismatch, capillary-valve pinning, and wall-associated wetting pathways reorganize the defending gas before it is displaced as a connected phase. We use a three-dimensional regularized color-gradient lattice Boltzmann model to examine these processes in a single, initially gas-saturated reconstructed tight-sandstone pore space. The simulations sample three capillary numbers, two or three Ohnesorge numbers depending on the capillary number, and two water-phase contact angles while keeping the water-to-gas viscosity ratio fixed at 26.11. The contact angle is measured through the aqueous phase, with θ = 20° representing strongly water-wet conditions and θ = 60° representing weakly water-wet conditions. For θ = 60°, terminal displacement efficiency changes little between the low and intermediate sampled capillary numbers and increases from approximately 0.660 to 0.736 at the highest sampled value. For θ = 20°, strong water-wetness is beneficial only after the bulk meniscus gains enough driving force to compete with precursor corner or wall flow; at a low capillary number, the same wetting affinity is associated with snap-off and premature gas isolation. The sampled Oh dependence is weaker than the Ca dependence and is consistent with conditional modulation of capillary-inertial damping and local interface relaxation; it is not interpreted as a new static entry criterion. Size-resolved and morphology-resolved statistics show contrasting terminal signatures: θ = 20° is associated with more large-pore gas and snap-off-consistent fragmentation, whereas θ = 60° is associated with more persistent small-pore gas and bypassing-consistent retention. Event-resolved phase-field sequences at one low-Ca condition directly show wall-first precursor advance, abrupt pore-body filling, gas-neck closure, persistent component splitting, and bypass-induced local entrapment. These events establish occurrence, not their frequency or dominance across parameter space. Because the study uses one pore-space realization and a sparse, non-factorial parameter matrix, the reported comparisons are restricted to the sampled conditions and do not define a continuous Ca–Oh–θ response surface or quantify structure-to-structure uncertainty.