Mineralization potential of water-dissolved CO2 and H2S injected into basalts as function of temperature: Freshwater versus Seawater

Mineralization of freshwater-dissolved gases, such as CO2 and H2S, in subsurface mafic rocks is a successful permanent gas storage strategy. To apply this approach globally, the composition locally available water must be considered. In study, reaction path models were run to estimate rate extent mineralization reactions during gas-charged freshwater seawater injection into basalts at temperatures 260, 170, 100, 25°C. The calculations validated by comparison field observations injections CarbFix2 site (Iceland). results show that more than 80% injected dissolved or mineralizes Ca Fe carbonates ≤170°C after 0.2 mol/kgw basalt, whereas 260°C much lower carbon rates are observed response same amount basalt dissolution. This difference due competition between carbonate versus non-carbonate secondary minerals epidote, prehnite, anhydrite for Ca. contrast, from 80 100% H2S predicted mineralized pyrite all fluid systems considered temperatures. Further with fluids having higher contents (equilibrated 9 bar pCO2) reveal i) pH buffered ≤6 precipitation Mg-rich aluminosilicates, which delays carbonation; ii) most efficient carbonation occurs <150°C formation likely significant