Visualizing multiphase flow and trapped fluid configurations in a model three-dimensional porous medium

TL;DR

This study uses confocal microscopy to visualize and analyze the pore-scale dynamics of two immiscible fluids flowing through a 3D porous medium, revealing how flow conditions affect trapped fluid structures.

Contribution

It introduces a method for direct 3D visualization of multiphase flow in porous media at pore-scale resolution, linking flow dynamics to trapped fluid configurations.

Findings

Trapped oil ganglia size decreases with increasing capillary number.

Residual oil amount is reduced at higher flow rates.

Flow dynamics influence trapped fluid morphology in porous media.

Abstract

We report an approach to fully visualize the flow of two immiscible fluids through a model three-dimensional (3D) porous medium at pore-scale resolution. Using confocal microscopy, we directly image the drainage of the medium by the non-wetting oil and subsequent imbibition by the wetting fluid. During imbibition, the wetting fluid pinches off threads of oil in the narrow crevices of the medium, forming disconnected oil ganglia. Some of these ganglia remain trapped within the medium. By resolving the full 3D structure of the trapped ganglia, we show that the typical ganglion size, and the total amount of residual oil, decreases as the capillary number Ca increases; this behavior reflects the competition between the viscous pressure in the wetting fluid and the capillary pressure required to force oil through the pores of the medium. This work thus shows how pore-scale fluid dynamics influence the trapped fluid configurations in multiphase flow through 3D porous media.