Effects of Pore-Scale Disorder on Fluid Displacement in Partially-Wettable Porous Media

TL;DR

This study investigates how pore-scale disorder affects fluid displacement efficiency in porous media, revealing that reducing disorder improves sweep and compactness, with wettability and flow rate influencing trapping and fingering phenomena.

Contribution

It introduces a quantitative assessment of pore disorder effects and proposes a modified capillary number incorporating disorder impact on viscous forces.

Findings

Reducing pore disorder enhances displacement efficiency.

Increasing wettability angle suppresses trapping and fingering.

Disorder influences the modified capillary number $ ext{Ca}^*$.

Abstract

We present a systematic, quantitative assessment of the impact of pore size disorder and its interplay with flow rates and wettability on immiscible displacement of a viscous fluid. Pore-scale simulations and micromodel experiments show that reducing disorder increases the displacement efficiency and compactness, minimizing the fluid-fluid interfacial area, through (i) trapping at low rates and (ii) viscous fingering at high rates. Increasing the wetting angle suppresses both trapping and fingering, hence reducing the sensitivity of the displacement to the underlying disorder. A modified capillary number $\mathrm{Ca^*}$ that includes the impact of disorder $\lambda$ on viscous forces (through pore connectivity) is direct related to $\lambda$, in par with previous works. Our findings bear important consequences on sweep efficiency and fluid mixing and reactions, which are key in applications such as microfluidics to carbon geosequestration, energy recovery, and soil aeration and remediation.