This study investigates the pore-scale dynamics and the influence of wettability and interfacial tension (IFT) on the two-phase immiscible displacement in radial flow through heterogeneous porous media using volume of fluid based numerical simulations. The numerical model was benchmarked with single-phase as well as two-phase flow experiments in a porous micromodel using micro-particle image velocimetry technique. The numerical velocity fields, interfacial shapes, and trapped-phase distributions closely matched the experimental observations, demonstrating the robustness and accuracy of the numerical model for pore-scale displacement predictions. Simulations were performed across a wide range of contact angles and IFT values. The results revealed a non-monotonic dependence of displacement efficiency on wettability, which has also been reported in some recent experiments. Our results show that weak imbibition gives the highest recovery due to cooperative filling, whereas strong imbibition led to early breakthrough caused by film-assisted flow. Neutral-wet and strong drainage conditions exhibited lower efficiencies dominated by fingering and large unswept zones. Reducing the IFT improved displacement efficiency and delayed breakthrough under both imbibition and drainage, but very low IFT induced a transition to viscous-dominated flow that weakened the capillary stabilization. The sensitivity to IFT followed the order: drainage neutral weak imbibition strong imbibition. These findings elucidate how wettability–IFT coupling governs the transition from capillary- to viscous-dominated regimes and controls invasion morphology at the pore scale.
Bhowmik et al. (Sun,) studied this question.