Wettability-driven pore-filling instabilities: Microfluidic and numerical insights

Abstract

Hypothesis

Interface dynamics, such as Haines jumps, are crucial in multi-phase flow through porous media. However, the role of intrinsic surface wettability in pore-filling events remains unclear, and the pressure response requires further study. This work evaluates the impact of wettability on interface stability and pressure dynamics.

Experiments and simulations

We performed microfluidic experiments and level-set simulations of two-phase flow. Water displaced air or Fluorinert in a PDMS micro-model with controlled wettability (contact angles: ${60}^{\circ }$, ${95}^{\circ }$, ${120}^{\circ }$). Three injection velocities covered capillary- to viscous-dominated flow regimes. High-resolution imaging and synchronized pressure recordings linked interface curvature with capillary pressure changes.

Findings

At low capillary numbers, wettability strongly affects burst pressure and pinning. Its influence decreases at higher capillary numbers. We observed an apparent wettability shift due to hysteresis and a capillary pressure barrier linked to pore-wall slope variations. Simulations replicated experimental trends, confirming the role of wettability in pore-scale displacement. These findings provide critical insights for improving pore-network models and understanding wettability effects in porous media.