Evolution of mechanical and hydraulic properties in sandstone induced by simulated mineral trapping of CO2 geo-sequestration

CO2 geological storage has been studied as a countermeasure against global warming. When the injected CO2 reacts with rock minerals, some portion of it may ultimately precipitate to carbonate minerals, such as calcite, and become trapped within the injected reservoir. Although it is of significant importance to examine how the trapped minerals exert an influence on the mechanical, hydraulic, and transport properties of the targeted reservoir rocks, because the minerals may affect the integrity of these rocks, such works are quite sparse in the literature. In this study, the influence of mineral trapping on the evolution of the physical properties was evaluated by replicating the precipitation of calcite that may occur in the mineral-trapping process. The calcite precipitation was enhanced artificially to occur within the void spaces of Berea sandstone. Subsequently, the treated samples were examined through mechanical and permeability experiments. The experimental results revealed that an approximately 10% substitution of the void spaces by the precipitated calcite increased the elastic modulus twofold and the uniaxial compressive strength (UCS) by 20%, and decreased the permeability by one order of magnitude. A cementation theory revealed the process of the calcite precipitation occurring on the free-surface of grains. Predictions of the permeability, using the Kozeny-Carman equation, suggest that variations in permeability imply an increase in surface roughness of the composed grains due to calcite precipitation.