SITE SPECIFIC GEOCHEMICAL MODELING OF GROUNDWATER, ROCK AND CARBON DIOXIDE INTERACTIONS: IMPLICATIONS FOR GEOLOGIC CARBON SEQUESTRATION

Geologic carbon sequestration is a process of mitigation that has the potential to reduce the impact of carbon dioxide emissions into the atmosphere through the injection of carbon dioxide into a saline aquifer.

This research utilized geochemical modeling of groundwater, rock and carbon dioxide interactions for geologic carbon sequestration purposes. Long term storage of carbon dioxide is an important requirement of geologic carbon sequestration. Because geochemical processes are responsible for the long term storage of carbon dioxide, it is necessary to understand the extent to which carbon dioxide can be trapped by geochemical trapping mechanisms. This study investigated the extent to which carbon dioxide can be sequestered in the Lamotte Sandstone, a Cambrian aged saline aquifer, due to solubility and mineral trapping. A comparison of the geochemical suitability of three well sites in North-Central Missouri was also conducted. The program Geochemist’s Workbench was used for the geochemical modeling simulations performed for this study. Site specific data such as temperature, carbon dioxide fugacity, pH, mineral content and groundwater composition were the input parameters needed to simulate the sequestration of carbon dioxide in a saline aquifer due to geochemical trapping mechanisms. Preliminary simulations have been performed for the first site and for both hypothetical injection and post injection phases of carbon sequestration.

For an example site, preliminary results show approximately 67 g/kg aqueous and 4 g/kg solid phase sequestered CO2, during the injection phase. Post injection phase results for this site indicate approximately 42 g/kg aqueous and 37 g/kg solid phase sequestered CO2. Aqueous species most involved in solubility trapping included CO2_(aq), HCO3-, NaHCO3, CaHCO3+, MgHCO3+ and FeHCO3+. Mineral species involved in mineral trapping included dawsonite, dolomite and siderite. For this example site a possible preliminary effective sequestration capacity was calculated as .36 gigatons per 100 km².

This material is based on work sponsored by the Department of Energy National Energy Technology Laboratory under Award Number DE-NT0006642 to City Utilities of Springfield MO.