Comparative effects of CO2 exposure on limestone and sandstone relevant to carbon sequestration in subsurface reservoirs

CO2-water-rock interactions can positively or negatively affect CO2 injection, storage capacity, and stability. This study examines the geochemical and microstructural responses of Indiana limestone and Berea sandstone when exposed to CO2-saturated water at 50 degrees C over 14 days. Elemental analysis revealed significant calcium dissolution in both rocks, with a slight stabilization at higher pressures in limestone and a marked reduction in Berea sandstone. While XRD analysis detected mild mineralogical changes, SEM analysis (at magnifications reaching up to 50,000x) revealed significant microstructural degradation, particularly pronounced in sandstone. These findings suggest that although CO2 exposure may initially enhance porosity, prolonged dissolution could compromise reservoir integrity, especially in siliciclastic sandstone formations. The observed differences in reactivity between the two rock types highlight the need for tailored CO2 sequestration strategies, including careful reservoir selection and assessments of long-term storage stability.