Dynamics of compression-driven gas-liquid displacement in a capillary tube

TL;DR

This study investigates how compression rate and reservoir volume influence gas-liquid displacement in a capillary tube, revealing two regimes separated by a critical compressibility number, with distinct displacement behaviors.

Contribution

It introduces a dimensionless compressibility number to characterize displacement regimes and identifies the transition between steady and burst-like expulsion.

Findings

Displacement dynamics depend on compression rate and reservoir volume.

Two regimes are identified: quasi-steady and burst-like expulsion.

A critical compressibility number separates the regimes.

Abstract

We study two-phase displacement via the steady compression of an air reservoir connected to an oil-filled capillary tube. Our experiments and modelling reveal complex displacement dynamics depending on compression rate and reservoir volume that, for large reservoirs, depend on a single dimensionless compressibility number. We identify two distinct displacement regimes, separated by a critical value of the compressibility number. While the subcritical regime exhibits quasi-steady displacement after an initial transient, the supercritical regime exhibits burst-like expulsion.