- © 2013 Mineralogical Society of America
The goal of geologic CO2 sequestration is not just to pump large volumes of supercritical carbon dioxide into underground repositories but to keep it there for hundreds to thousands of years, preferably in chemically bound form. The permanence of CO2 storage in geological repositories is important since large leakage rates would diminish the CO2 abatement achieved with carbon capture and sequestration (CCS). Effective permanent geologic CO2 storage depends ultimately on the interactions of the supercritical CO2 with the minerals and fluids present in the host underground repositories and their caprock sealing (Xu et al. 2005; Kharaka et al. 2006, 2010; Benson and Cole 2008). Migration of supercritical CO2 within these geological repositories is controlled by confinement/trapping of CO2 in the porous structure as well as solubility of CO2 in the fluids (brine and hydrocarbons) already present in the storage formation (Cole et al. 2010; Doughty 2010). In deep saline aquifers, the dissolution of CO2 in water generates carbonic acid, which in turn reacts with minerals such as clay, mica and feldspar and carbonates present in the reservoir rocks to generate cations and carbonate/bicarbonate ions (Kaszuba et al. 2003, 2005; Kharaka et al. 2006; Ketzer et al. 2009; Cole et al. 2010; Doughty 2010). Finally, precipitation of metal carbonate occurs either by direct or indirect reaction of the CO2 with other minerals and organic matter present in the reservoirs (Garcia et al. 2012; Kharaka et al. 2010; Shao et al. 2010, Xu et al. 2004, 2005).
It is essential to understand and predict the chemical reactions and stability of mineral phases formed under sequestration conditions as these could affect the migration of CO2 and the seal …