| Summary: | A huge amount of CO2 emissions should be mitigated for environmental benefits and to reach net zero by 2050. One method to mitigate these emissions is permanent CO2 sequestration through mineralization. CO2 can be mineralized as carbonate minerals such as calcite and magnesite if injected into igneous formations rich in reactive minerals such as olivine, pyroxene and plagioclase. The dissolution of CO2 in brine is the first geochemical reaction in the pore space that leads to CO2 mineralization eventually. The objective of this study is to understand the dynamics and controlling parameters of CO2 dissolution in brine and mineralization in mafic basaltic formations. This study uses a 3D carbon sequestration numerical model to simulate the geochemical reactions of injecting CO2 into a saline aquifer in a basaltic formation. The model includes three main geochemical reactions: CO2 dissolution in water, dissolution of formation minerals, and precipitation of carbonate minerals. The first reaction results in forming carbonic acid that reacts with the formation minerals: anorthite, wollastonite, pyroxene, and olivine, which results in releasing calcium and magnesium ions. The reaction between divalent cations and dissolved CO2 in brine results in precipitating carbonate minerals: magnesite and calcite. CO2 is injected into the formation for four years and simulated for 200 years. The dynamics of reservoir pressure and CO2 plume migration are studied as CO2 mineralizes. In addition, the rate of mineral dissolution and precipitation is analyzed as the initial conditions of the reservoir change, including brine salinity, temperature, and pH. In addition, the change in porosity and permeability is investigated during CO2 mineralization process. The results show that 95% of the injected CO2 is mineralized within the first 7 years. After 200 years, 98% of injected CO2 is mineralized, 1.5% is dissolved in brine and 0.5% is residually trapped. Due to the mineralization of CO2 in the form of magnesite, and calcite, the ...
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