Graduation Year

2010

Document Type

Thesis

Degree

M.S.E.V.

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Jeffrey Cunningham, Ph.D.

Co-Major Professor

Mark Stewart, Ph.D.

Committee Member

Maya Trotz, Ph.D.

Keywords

carbon capture and storage, activity coefficient, CO2 solubility model, mineral precipitation and dissolution, geochemistry, non-linear

Abstract

Geologic sequestration of carbon dioxide (CO 2) in a deep, saline aquifer is being proposed for a power-generating facility in Florida as a method to mitigate contribution to global climate change from greenhouse gas (GHG) emissions. The proposed repository is a brine-saturated, dolomitic-limestone aquifer with anhydrite inclusions contained within the Cedar Keys/Lawson formations of Central Florida. Thermodynamic modeling is used to investigate the geochemical equilibrium reactions for the minerals calcite, dolomite, and gypsum with 28 aqueous species for the purpose of determining the sensitivity of mineral precipitation and dissolution to the temperature and pressure of the aquifer and the salinity and initial pH of the brine. The use of different theories for estimating CO2 fugacity, solubility in brine, and chemical activity is demonstrated to have insignificant effects on the predicted results. Nine different combinations of thermodynamic models predict that the geochemical response to CO2 injection is calcite and dolomite dissolution and gypsum precipitation, with good agreement among the quantities estimated. In all cases, CO2 storage through solubility trapping is demonstrated to be a likely process, while storage through mineral trapping is predicted to not occur. Over the range of values examined, it is found that net mineral dissolution and precipitation is relatively sensitive to temperature and salinity, insensitive to CO2 injection pressure and initial pH, and significant changes to porosity will not occur.

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