Reactive transport modelling of CO2-enriched condensate reinjection in andesitic geothermal reservoirs towards the enhancement of carbon mineralisation

This study applies reactive transport modelling to investigate the geochemical and hydrodynamic impacts of CO2-enriched condensate reinjection into andesitic geothermal reservoirs, building on a high-temperature flow-through experiment using steam condensate and Southern Negros andesite at 230 °C and 200 bar. The calibrated model of the experiment resulted in significant quartz dissolution and secondary minerals deposition, with the magnitude of the dissolution being higher than the deposition, resulting in an increase in permeability. This calibrated model served as the basis for our fluid-rock interactions simulations under evolving CO2 conditions and additional chemicals. The model explores how increasing CO2 concentrations in the injected fluid influence fluid pH, mineral dissolution and precipitation trend, and permeability. We found that (i) a certain amount of CO2 could enhance calcite dissolution but promote anhydrite precipitation, (ii) increasing the CO2 mineralisation by adding Ca(OH)2 initiated mineralisation in the form of calcite, and (iii) the highest mineralisation was achieved by injecting the same moles of Ca(OH)2 with the injected CO2 and SO4 2-. This experimental-modelling approach enhances our understanding of reactive surface area evolution, CO2 storage mechanisms, and their effect on the reservoir performance in geothermal systems.