Coupled dynamics of colloids and immiscible fluids in porous media

Abstract

A wide array of processes, from contaminant transport to carbon dioxide sequestration and groundwater remediation, involve interactions between colloidal particles and immiscible fluids. In these applications, colloidal particles and immiscible fluids must navigate complex, tortuous, three-dimensional (3D) pore spaces, such as in soils and rigid rocks. For simplicity, researchers typically study these interactions using individual particles in idealized geometries. While these studies help to elucidate the physics underlying these interactions—including colloidal interactions, hydrodynamics, and capillarity—in many cases, concentrated deposition of colloids and complex pore space geometries give rise to phenomena that cannot be described by simplified models. In this dissertation, I address this gap in knowledge by studying how colloidal deposition impacts immiscible fluid flow and mobilization in porous media by integrating experiments, simulations, and theory. First, by injecting colloids into a model porous medium containing trapped immiscible fluid droplets, I show that colloidal deposition can be controlled and harnessed to enhance removal of trapped droplets by reducing the medium’s overall permeability. Building upon the theoretical framework developed to describe immiscible fluid mobilization, I next explore how structural heterogeneity within a porous medium may impact the accuracy of those predictions. Then, using this foundational understanding of colloidal flows and immiscible fluid trapping, I develop pore scale experiments and simulations that describe how immiscible fluid flow is altered by the ability of fluid-fluid interfaces to erode and redeposit colloidal particles. I show that colloidal particles can be driven to fluid interfaces by capillary forces, which results in the emergence of a new immiscible fluid flow regime and expands upon traditional models to describe immiscible fluid flow. Having extensively explored the interactions between colloids and immiscible fluids in porous media, I fabricate hybrid colloidal particles containing catalytically active metal nanoparticles and an organic, polymeric support, demonstrating a tunable method to produce hybrid nanoparticles for groundwater remediation. Finally, my ongoing work discusses how to study the efficacy of reactive particles for immiscible contaminant degradation in 3D porous media. These results present a unified chemical and physical approach to understanding how colloids interact with and impact immiscible fluid flow in porous media.