Abstract
Effective predictive modeling of CO₂ storage sites requires a comprehensive understanding of the physico-chemical processes and the challenges of scaling up operations. In high-salinity aquifers, CO₂ injection can significantly reduce injectivity due to pore clogging from salt precipitation. This study investigates the effects of CO₂-induced salt crystallization on the geomechanical properties of sandstone reservoirs. We examine the geochemical and mechanical coupling effects through CO₂-brine-rock interactions, utilizing two experimental paths: treatment with (a) CO₂-acidified brine and (b) supercritical injection leading to salt crystallization. High-pressure, high-temperature (HPHT) triaxial tests were conducted on Boise Buff (BB) and Torrey Red (TR) sandstones, representative of North Sea CO₂ storage candidates. The results showed up to a 50% reduction in Young’s and shear moduli, with TR sandstones being more susceptible due to their lower porosity and higher stiffness. An increase in ductility suggests mechanical weakening and potential storage integrity risks. These findings highlight the containment and integrity challenges posed by salt crystallization in (hyper)saline aquifers beyond injectivity issues, emphasizing potential mechanical failure risks due to pressure buildup. The study underscores the importance of incorporating geochemical interactions into CO₂ storage assessments and reservoir management strategies to mitigate these risks.