MODELING SOLUBILITY AND MINERAL TRAPPING OF CO2 AT A PROPOSED CARBON SEQUESTRATION SITE IN SW MISSOURI

A hypothetical reservoir intended to closely resemble the Lamotte Sandstone in SW Missouri was used to investigate the capability of a shallow reservoir to sequester carbon. The site is located in Springfield, Missouri, and the target formation is found at about 600 m depth, significantly less deep than the approximately 800 m depth needed to sequester CO₂ as a supercritical fluid. In absence of specific water chemistry and lithology data for this formation at the proposed injection site, we considered two best estimates of each as input parameter. We used the geochemical model The Geochemist’s Workbench^® and we assumed a 10-year injection period and a 50-year post-injection period. After the 10 year injection period, the CO₂ sequestered in the dissolved phase was found to vary between 76.7 and 76.8 g/kg free water, and the pH dropped from 7.7 to 4.8. During the 50-year post-injection interval with no additional CO_2(g) added, the model predicted the pH to rise from 4.8 to 5.3 and various minerals to precipitate, among them magnesite, nontronite-Mg and gibbsite, as well as smaller amounts of siderite and dolomite. Magnesite, siderite, and dolomite contribute to removal of carbon. The Missouri Carbon Sequestration Project is ongoing and contemplates drilling of several wells to fully characterize the site. To determine total sequestration potential, transport modeling is needed in addition to the geochemical modeling presented here. This material is based upon work sponsored by the Department of Energy National Energy Technology Laboratory under Award No. DE-NT0006642 to City Utilities of Springfield, MO.