Manipulation of Viscous Fingering in a Radially-Tapered Cell Geometry

TL;DR

This study demonstrates how a radially-tapered cell geometry can suppress viscous fingering during fluid displacement, enabling full sweep and controllable instability through flow rate and gap gradient adjustments, with results aligning with theoretical predictions.

Contribution

It introduces a novel experimental approach using a radially converging cell to control viscous fingering, providing insights into stability thresholds and flow manipulation.

Findings

Radially converging geometry suppresses viscous fingering.

Flow rate $Q$ influences the stability and extent of displacement.

Critical threshold between stable and unstable displacement varies with gap gradient $oldsymbol{eta}$.

Abstract

When a more mobile fluid displaces another immiscible one in a porous medium, viscous fingering propagates with a partial sweep, which hinders oil recovery and soil remedy. We experimentally investigate the feasibility of tuning such fingering propagation in a non-uniform narrow passage with a radial injection, which is widely used in various applications. We show that a radially converging cell can suppress the common viscous fingering observed in a uniform passage, and a full sweep of the displaced fluid is then achieved. The injection flow rate, $Q$, can be further exploited to manipulate the viscous fingering instability. For a fixed gap gradient $\alpha$, our experimental results show a full sweep at a small $Q$ but partial displacement with fingering at a sufficient $Q$. Finally, by varying $\alpha$, we identify and characterize the variation of the critical threshold between stable and unstable displacements. Our experimental results reveal good agreement with theoretical predictions by a linear stability analysis.