Reactive transport modelling of CO2 sequestration in Deccan Basalt: Mineral trapping vis-à-vis reservoir conditions and injection strategies

• Simulates mineral volume fraction evolution over 250 years for storage assessment. • Provides insights for CCS implementation in India’s Deccan basalt formations. • Cyclic CO 2 injection enhances mineral reactivity and carbonate precipitation over continuous mode. • Low porosity/permeability boosts carbonate formation but raises reservoir pressure risks. The Deccan basalt formations in India offer significant potential for permanent geological CO 2 sequestration (GCS) through mineral trapping, in which injected CO 2 reacts with silicate minerals to form stable carbonates. However, fundamental gaps remain in understanding how reservoir conditions and injection strategies influence mineral carbonation efficiency over extended timescales. This study aims to bridge this gap by quantifying the impact of reservoir conditions and injection strategies on mineralisation rates. To conduct this study, the multiphase, multicomponent reactive transport simulations are used to analyse CO 2 -basalt-brine interactions over 250 years. The numerical model incorporated mineralogical data consisting of plagioclase, pyroxene, and magnetite to assess the sensitivity of mineral trapping to variations in temperature, pressure, pH, and petrophysical properties. Results indicated that reservoir temperature is a primary control on reaction kinetics; at moderate temperatures (57°C), it favours the precipitation of stable secondary carbonates (calcite, aragonite) due to enhanced CO 2 solubility, whereas higher temperatures (75°C) predominantly accelerate primary silicate dissolution. Further in the results, a crucial comparative analysis of injection strategies is carried out, demonstrating that a cyclic CO 2 injection scheme yields higher efficiency than continuous injection. The periodic idle phases in the cyclic strategy allow the system to re-equilibrate, enhancing overall mineral reactivity and trapping capacity. Additionally, in studies of the influence of petrophysical properties, it has been observed that lower permeability conditions increase localised mineral precipitation due to greater resident time contact between the water-CO 2 -rock, though this may entail trade-offs in injectivity. These findings underscore the importance of site-specific optimisation and suggest that cyclic injection is a viable strategy for maximising the sequestration potential of the Deccan basalts.