Intricacies of CO2-Basalt Interactions, Reactive Flow and Carbon Mineralization: Bridging Numerical Forecasts to Empirical Realities

Subsurface fluid flow and solute transport are pivotal in addressing pressing energy, environmental, and societal challenges, such as geological CO2 storage. Basaltic rocks have gained prominence as suitable geological substrates for injecting substantial CO2 volumes and carbon mineralization, driven by their widespread occurrence, high concentrations of cation-rich silicate minerals, reported fast mineralization rate, and favorable characteristics such as porosity, permeability, and injectivity. The mineralization process within basaltic rocks is intricately linked, involving the dissolution of silicate minerals and the subsequent precipitation of carbonate minerals. Columnar flow and batch surface growth experiments revealed the spontaneous formation of a limited number of large crystals at various locations, rationalized by the overarching influence of probabilistic mineral nucleation. Experiments with CO2-acidified brine versus freshwater prove to be more challenging regarding the sweet spots for heavy carbon mineralization due to clay formation on the surface, particularly smectites. Despite numerical predictions suggesting the formation of MgFeCa-carbonates in CO2-basalt interactions at higher temperatures, our laboratory findings primarily indicated the growth of calcium carbonates. The experimental and numerical outcomes highlight the necessity of a probabilistic approach for accurately modeling reaction kinetics, crystal growth distribution, and the dynamic interplay between reactive flow, geochemical reactions, mineral carbonation, and geometry alteration.