Security of Geological CO2 Storage is Enhanced via Self-Sealing Caprock Mineral Reactive Transport Mechanisms

Abstract

Abstract

Abstract The long-term security of geological CO2 storage hinges on the integrity of caprock formations, traditionally considered vulnerable to acid-induced dissolution from injected CO2 and associated impurities. Contrary to this view, we demonstrate that impurity-bearing CO2 can enhance caprock integrity through mineralization-driven self-sealing. Reactive transport modeling across three CO2 storage sites shows that silicate minerals, particularly smectite and chlorite, facilitate the precipitation of sealing carbonates such as ankerite and magnesite. These pore-filling reactions are sustained by divalent cations released from calcium-, iron-, and magnesium-rich aluminosilicates, progressively reducing pore connectivity and CO2 diffusivity. We show that, over a 100-year period, CO2 diffusion in reactive caprocks decreases by approximately 0.8-1 order of magnitude. We propose an empirical relationship describing the time-dependent decline in diffusion. As these mineral assemblages are common in seal rocks globally, the identified self-sealing mechanisms significantly lower leakage risk and provide a broadly applicable pathway for improving long-term CO2 containment. This work reframes impurity-bearing CO2 not as a threat, but as a catalyst for subsurface resilience, opening new avenues for designing safer and more adaptive carbon storage systems.