Flow, Distribution, and Storage of Carbon Underground

Abstract

As we attempt to transition to a future of low greenhouse gas emissions, carbon dioxide removal (CDR) is projected to play a key role in addressing historical emissions and emissions that will be difficult to avoid. In this thesis, I examine geochemical and geophysical phenomena underlying two CDR strategies. Relatively long molecular dynamics (MD) simulations are used to explore a range of capillary properties and characterize systems of water and carbon dioxide in quartz nanopores in detail. First, different scales of observations in these systems are linked, and then various organic solutes are incorporated. The findings from these studies show that MD can be used to accurately capture macroscopic capillary and multi-phase flow properties, while providing atomistic information. These methodologies allow the discrepancies between nano- and continuum scale descriptions of wetting to be linked to the disjoining pressures within adsorbed water films on mineral surfaces. The redistribution of organic solutes in these systems also reveal the strong preference of organic matter and contaminants for the curved water-CO2 interfaces. Organic solutes that coat the CO2 bubble evenly in our studies are able to be brought into increased contact with the unique environment of the adsorbed water film between the CO2 bubble and the quartz surface. The adsorption of organics to the water-CO2 interface is usually accompanied by a simultaneous desorption of CO2 from the interface, resulting in less change to the interfacial tension than would be expected at water-air interfaces. In addition, non-equilibrium MD simulations are employed to demonstrate how surface active organic solutes can modulate advancing and receding contact angles. Lastly, a surface-level terrestrial CDR method is considered by collecting and harmonizing field data on common agricultural soil carbon sequestration strategies, enabling the analysis of potential nitrogen limitations. This work links different scales of data and observations motivated by elucidating the fundamental basis of two CDR strategies with high estimated potential for mitigating emissions.