Capillary-Driven Instability of Immiscible Fluid Interfaces Flowing in Parallel in Porous Media

TL;DR

This paper investigates the capillary-driven instability that occurs when immiscible fluids flow in parallel through porous media, leading to interface mobilization and bubble formation at high capillary numbers.

Contribution

It introduces a detailed analysis of the instability mechanism and characterizes the boundary zone dynamics between wetting and non-wetting fluids in porous media.

Findings

Boundary zone with bubbles has a well-defined thickness.

The zone moves at a constant average speed.

A diffusive current of non-wetting bubbles into the wetting fluid is observed.

Abstract

When immiscible wetting and non-wetting fluids move in parallel in a porous medium, an instability may occur at sufficiently high capillary numbers so that interfaces between the fluids initially held in place by the porous medium are mobilized. A boundary zone containing bubbles of both fluids evolve which has a well defined thickness. This zone moves at constant average speed towards the non-wetting fluid. A diffusive current of bubbles of non-wetting fluid into the wetting fluid is set up.