In-situ carbon mineralization through injection of CO₂-saturated water into basalts: Effects on pore network

Carbon capture and storage (CCS) offers the potential to remove and safely store significant quantities of carbon dioxide from the atmosphere, thereby limiting global warming. Conventional geological storage involves injecting CO₂, in gaseous or supercritical state, into porous rock reservoirs, relying on geological top seals, capillary forces and/or dissolution in groundwater as the primary "locking-in" processes. An alternative method injects CO₂-saturated water into mafic rocks (basalts), chemically inducing in-situ mineralization of CO₂ to form solid carbonate minerals. This mechanism offers the lowest risk of carbon returning to the atmosphere. This review synthesizes field and laboratory studies on CO₂ mineralization in basaltic rocks and the resulting impact on the rock's pore network, permeability and porosity. Evidence indicates that dissolution-precipitation reactions substantially alter basalt microstructure, with outcomes strongly influenced by (i) sufficient fluid residence time within the pore space, (ii) adequate reactive surface area, including both total rock surface and reactive mineral phases, and (iii) in-situ permeability and porosity that enable efficient CO₂-saturated water injection with minimal energy input. While dissolution enhances pore connectivity and injectivity, secondary carbonate precipitation can clog flow pathways, though fracture opening under pressure-temperature gradients may counteract these effects. Field-scale projects such as CarbFix demonstrate that continuous dissolved-CO₂ injection promotes near-well dissolution while shifting carbonate precipitation farther from the injection site, reducing clogging risks. Current findings highlight basaltic formations as promising, safe, and scalable reservoirs for permanent CO₂ storage, though further research is needed to quantify pore-scale processes and optimize injection strategies.