CarbFix2: CO2 and H2S mineralization during 3.5 years of continuous injection into basaltic rocks at more than 250 degrees C

摘要

The CarbFix method was upscaled at the Hellisheioi geothermal power plant to inject and mineralize the plant's CO2 and H2S emissions in June 2014. This approach first captures the gases by their dissolution in water, and the resulting gas-charged water is injected into subsurface basalts. The dissolved CO2 and H2S then react with the basaltic rocks liberating divalent cations, Ca2+, Mg2+, and Fe2+, increasing the fluid pH, and precipitating stable carbonate and sulfide minerals. By the end of 2017, 23,200 metric tons of CO2 and 11,800 metric tons of H2S had been injected to a depth of 750 m into fractured, hydrothermally altered basalts at >250 degrees C. The in situ fluid composition, as well as saturation indices and predominance diagrams of relevant secondary minerals at the injection and monitoring wells, indicate that sulfide precipitation is not limited by the availability of Fe or by the consumption of Fe by other secondary minerals; Ca release from the reservoir rocks to the fluid phase, however, is potentially the limiting factor for calcite precipitation, although dolomite and thus aqueous Mg may also play a role in the mineralization of the injected carbon.