Evaluating the impact of CO2 on the geomechanical and geochemical properties of different rock types

Abstract

The interaction between CO₂ and water in subsurface environments plays a critical role in altering the geomechanical properties of rocks, with significant implications for carbon sequestration, reservoir integrity, and underground storage applications. This study evaluates the impact of CO₂-water exposure on the strength, elasticity, porosity, and mineralogical composition of different rock types, including sandstone, limestone, dolomite, basalt and shale. Laboratory experiments were conducted to characterize the initial petrophysical and geomechanical properties of the rock samples before subjecting them to CO₂-saturated water under controlled pressure and temperature conditions. Post-exposure analyses were performed using nanoindentation SEM-EDS and X-ray diffraction (XRD) to assess mineralogical and structural changes. The results indicate that CO₂-water interaction leads to varying degrees of mechanical weakening, with carbonate rocks showing significant dissolution effects and reduced elastic modulus. In contrast, silicate-rich rocks like sandstone exhibited comparatively lower degradation due to their mineralogical stability. These findings highlight the importance of rock-specific evaluations in subsurface engineering applications, particularly in optimizing CO₂ storage strategies and ensuring long-term stability. Further studies incorporating extended exposure durations and field-scale validation are recommended to enhance predictive models for rock behavior in CO₂-rich environments.