Effect of Flow Dynamics on Two‐Phase Flow Patterns in Porous Media

Abstract

This study investigates the impact of flow dynamics on liquid‐gas two‐phase flow patterns within a two‐dimensional millifluidic porous medium. Based on high‐fidelity analysis of experimental images and simplified single‐phase flow pore network models (PNM), we examine co‐injection two‐phase flow configurations across varying injection rates and initial conditions to elucidate the relationship between spatial phase configuration and dynamic intermittent multiphase flow features. The experiments reveal that, within a capillary number (Ca) range of to , changes in the global amplitude of the imposed flow rates by one order of magnitude does not significantly affect the size distribution of the pores filled by one phase or the other. While the non‐wetting phase (gas) typically occupies larger pores than the wetting phase due to capillary forces, the resulting spatial distributions of the phases and the phase‐filled pore size distributions remain similar across different flow dynamics (for similar saturation degrees). Analysis of the entrapped non‐wetting clusters indicates that their lengths can be evaluated based on the interplay between the typical capillary pressure across fluid‐fluid interfaces and the pressure gradient within the liquid (wetting). Furthermore, while the specific paths followed by moving fluid‐fluid interfaces vary with flow dynamics, the pore and throat size distributions along these paths differ only slightly from those of the fully saturated medium. These findings may suggest that the spatial configuration of fluid phases and displacement of their interfaces are predominantly controlled by local energy considerations at the moving front, rather than by a simple global energetic pathway‐selection signal. Finally, the study demonstrates that relative permeability is strongly correlated with the area fraction of dead‐ends and the ratio of saturation to hydraulic tortuosity, but is largely independent of the specific flow regime.