CO2 Injection and Production in Geothermal Reservoirs for Power Generation: Case Study From North Sumatra Basin of Possible Impacts of Scaling on Surface Facilities

The increasing energy demand in Indonesia comes with a large amount of anthropogenic CO2 emission which Indonesia has committed to reduce by 29% in order to meet the carbon emission target according to the BaU scenario of Indonesia's NDC (Nationally Determined Contribution) by the year 2030. Indonesia has abundant geothermal energy potential and sources of anthropogenic carbon dioxide from various industries. Based on recent trends and the latest references, supercritical carbon dioxide (scCO2) is feasible to inject into geothermal reservoirs to scavenge heat, and then produced as a working fluid to generate electricity in a process called Enhanced Geothermal System (EGS). The complex CO2–induced geochemical reactions can cause a change in reservoir porosity and affect fluid flow and heat mining rate. In this study, a comprehensive investigation on geochemical interactions between CO2–water as well as conceptual facilities of CO2 turbine was conducted. A water scaling simulation model was built to simulate the geochemical reactions in surface facilities during the CO2–EGS process. Mineral composition from several wells were modeled to calculate Saturation Index (SI) as a parameter that would indicate whether the mineral would tend to dissolve or precipitate. The geochemical simulation showed that in a North Sumatra geothermal field tested using scCO2 as a working fluid, the presence of CO2 could change water properties ( pH and alkalinity )– which could then induce the precipitation of calcium carbonate, dolomite, and silicon dioxide. The concept of using carbon captured CO2 as a working fluid for geothermal powerplant is quite new and mineral scaling due injected CO2 is an aspect that needs to be further investigated.