Hydrogeochemical control on mean stress dependent permeability and mechanical response in eolian sandstone during reaction with CO2-enriched fluid

Carbon Capture, Utilization, and Storage (CCUS) is one of the main technologies being deployed to reduce greenhouse gas emissions. Although the number of operational facilities is quickly growing, guidance from the International Energy Agency suggests that global efforts must be drastically increased to be a critical component in reducing total emissions. A primary component of successfully increasing CCUS is site characterization, including an assessment of hydro-chemomechanical weakening to verify that a reservoir-caprock system is sufficient for long-term storage and to understand site-specific risks. In this study, we use multiphysics High Pressure High Temperature (HPHT) flow-through experiments to characterize the Entrada Sandstone to better understand its geochemical, mechanical, and hydraulic sensitivity to CO 2 storage. We conducted flow-through experiments on two lithofacies using both a CO 2 -enriched and unenriched synthetic reservoir fluid, combined with permeability and deformation monitoring, forensic petrographic characterization, X-ray computed tomography, and petrophysical analysis. The hydrogeochemical evolution during our experiments resulted in changes in permeability at in-situ conditions as well as significant changes in the mean stress dependence of permeability before and after the experiments. Most significantly, all samples appeared to lose a strong mean stress dependence after the flow-through experiments. Additionally, there were measurable strain accumulation and changes in elastic properties. We relate strain evolution, changes in rock mechanical properties, and permeability evolution to the samples’ diagenetic history, the mechanical deformation and swelling behavior of the clay cement in H 2 O and CO 2 -H 2 O conditions, and fluid flow rate during the experiments.