Wettability-driven pore-filling instabilities
Microfluidic and numerical insights
Lifei Yan (TU Delft - Reservoir Engineering, Universiteit Utrecht)
Johannes C. Müller (University of Stuttgart)
Tycho L. van Noorden (COMSOL B.V.)
Bernhard Weigand (University of Stuttgart)
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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∘, 95∘, 120∘). 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.
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