Events Calendar

PhD Defense

Speaker: Zhuofan Shi , PhD Candidate, Chemical Engineering

Talk Title: The Study of CO2 Mass Transfer in Brine and in Brine-Saturated Mt. Simon Sandstone and the CO2/Brine Induced Evolution of its Transport and Mechanical Properties

Abstract: Emissions of greenhouse gases are thought to contribute to global warming. Geological carbon sequestration (GCS) is currently considered a promising method to mitigate atmospheric CO2 and, thus, to potentially minimize climate change. In this approach, CO2 is injected into the subsurface and is trapped there by three main mechanisms, namely physical trapping, dissolution, and mineral precipitation.
The present work focuses on two important aspects of GCS. First, we study mass transfer and sorption phenomena in brine, which are the key two processes occurring during CO2 dissolution trapping in GCS. We employ pressure-decay experiments to measure CO2 solubility, and mass transfer in water/brine systems at elevated pressures of relevance to CO2 storage operations in saline aquifers together with modeling to delineate and interpret the experimental data. Accurate measurements and modeling of mass transfer in this context are crucial to an improved understanding of the long-term fate of CO2 that is injected into the subsurface for storage purposes. We demonstrate that simple 1-D interpretations based on diffusional transport alone can result in an overestimation of the uptake (diffusivity) by two orders of magnitude. The high-resolution 2-D numerical calculations, on the other hand, agree well with the experimental observations for conditions where natural convection contributes substantially to the overall mass transfer process.
We also study, in addition, rock-fluid interactions and their impact on the transport and mechanical properties of the host rock, which are phenomena relevant to CO2 mineral trapping during GCS. Specifically, the present study investigates the change in the flow-through characteristics, porosity, and the mechanical behavior of Mt. Simon Sandstone samples caused by exposure to brine/CO2. Our experiments show that the porosity of the Mt. Simon samples slightly increases after exposure to CO2/brine, while the permeability increases more substantially (depending on the confining pressure environment). Measurements of the flow-through pore size distribution (PSD) are indicative of significant changes occurring, consistent with the observed increases in permeability. Nitrogen adsorption tests (BET), before and after aging, show a significant loss of pore volume in the mesopore range that is indicative of clay dissolution. Weakening of the materials was observed based on the mechanical properties studied, a result that is consistent with the observed dissolution of clays that play a central role in the cementation of the quartz grains. Finally, the analysis of the brine compositions employed in the aging experiments reveals an increase in the concentration of most cations after incubation with the Mt. Simon cores. This is also consistent with mineral/clay dissolution, confirmed by the porosity, transport, and mechanical property measurements as well as electron microscopy analysis of the same samples.

Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 303

Audiences: Everyone Is Invited

Contact: Karen Woo/Mork Family