Perpustakaan Digital ITB

Carbon Capture and Storage (CCS) is one of the main strategies for reducing anthropogenic CO2 emissions, and mineral trapping in volcanic reservoirs offers the most permanent form of storage. This study develops a geochemical reactive transport model of CO2-brine-basaltic rock interaction in the Ungaran geothermal field, Central Java, Indonesia, using TOUGHREACT with the ECO2N fluid property module. The reservoir is represented as a one-dimensional radial domain with a single injection well, using the published mineralogy and conditions of the field, and CO2 is injected continuously at 90 kg/s for 30 years. The simulation shows that CO2 dissolution lowers the brine pH and raises the dissolved bicarbonate concentration, indicating solubility trapping, while the acidic conditions drive the dissolution of anorthite and the precipitation of calcite (with kaolinite as a by-product), indicating mineral trapping. These reactions are concentrated in a reaction zone that migrates outward from the injection well, where the porosity decreases from about 0.10 to 0.090 (about 10%) and the permeability is reduced by about 27%. Within the reacted zone, the mineralized fraction rises from about 31% at 10 years to about 69% at 30 years, so mineral trapping becomes the dominant form of storage over the simulated period. The distribution of the two trapping mechanisms along the radius is resolved in space and time, a result that static batch modeling cannot provide.