Effects of nanoscale reactions on geophysical characteristics at geologic sequestration sites

Devising effective mitigation strategies for the anthropogenic CO₂ are imperative. Although geologic CO₂ sequestration (GS) is promising, we still do not have a holistic understanding of potential reactions in GS. In this study, we investigated the mechanisms, kinetics, and environmental impact of interfacial reactions among CO₂-water-mineral surfaces at the molecular scale. By incorporating aqueous chemistry with in situ x-ray scattering and atomic force microscopy, we monitored real-time nanoscale morphological changes resulting from dissolution of pre-existing minerals and precipitation of new mineral phases. The physico-chemical property changes of reference minerals and field site samples from the Illinois Basin were studied. After caprock samples were in contact with CO₂ saturated saline water at 80°C for 14 days, the concentrations of dissolved metals increased up to 47,000 ppm. The experimental results suggest that monitoring the early stage of interfacial reactions is crucial to understanding the CO₂-water-rock interactions in GS.