InterPore2025

Miscible pore-scale flow and transport under variable fluid viscosity

22 May 2025, 10:35

1h 30m

Poster Presentation (MS11) Microfluidics and nanofluidics in porous systems Poster

Speaker

yaniv edery (Technion)

Description

Miscible multiphase flow in porous media involves displacing a resident fluid by another fluid of different viscosity and density. This process arises in various applications, such as groundwater remediation, hydrogen storage, moisture and solute transport, and geological carbon sequestration, where mixing leads to an intermediate fluid phase distinct from the original phases, thus changing the pH in a non-trivial way (1). When a less viscous fluid displaces a more viscous one, instability at the fluid–fluid interface can create pronounced “viscous fingering” patterns.
Experiments on miscible phase flow in porous media highlight the role of flow rate and heterogeneity, which also shape the emergence of fingering patterns associated with miscible phase flow. These investigations showed how a transition from homogeneous to heterogeneous pore structure leads to a uniform or finger-like invasion and how inlet pressures affect both mixing and invasion patterns, with equivalent flow rates observed at the Darcy scale. Extending this approach, the present work analyzes the impact of changing viscosity caused by mixing on the formation and suppression of fingers in a 2D porous medium. We derive solutions for the expected flow rates in a regular and irregular porous medium during the miscible displacement, as a low-viscosity fluid displaces a more viscous fluid. The derivation is based on solving the time-dependent Darcy equation over two conductivity blocks in series or parallel to capture the uniform and finger formation, respectively. This simplified solution captures well how the evolving viscosity influences hydraulic conductivity, thereby either suppressing or initiating finger formation. This solution not only captures well the experimental flux, but also the mean viscosity in the flow cell. These findings align with the effective diffusion coefficient and effective Sherwood number framework introduced previously (2).
1. A. Biran, T. Sapar, L. Abezgauz, and Y. Edery, Experimental investigation of the interplay between transverse mixing and pH reaction in porous media, EGUsphere , 1 (2024), publisher: Copernicus GmbH.
2. Y. Eliyahu-Yakir, L. Abezgauz, and Y. Edery, From mixing to displacement of miscible phases in porous media: The role of heterogeneity and inlet pressures, Physical Review Fluids 9, 084501 (2024), publisher: American Physical Society