CO2 is one of the main greenhouse gases causing climate change and its efficient removal from the atmosphere will determine whether the goals set in the Paris Agreement can be reached or not. By capturing and permanently storing CO2 right after its generation, either from power plants or industry-related processes which require large amounts of fossil energy or produce CO2 in the chemical reactions that take place during the manufacturing of products, a neutral carbon footprint can be achieved. Geological carbon storage can be achieved by injecting CO2 in underground reservoirs such as aquifers or depleted gas reservoirs. However, due to the low density of CO2, it is naturally buoyant and creates a plume as the topmost component of the reservoir. Due to this buoyancy, the presence of a tight seal rock is essential in the traditional storage concept, thus preventing an escape of the CO2. Alternatively, storing CO2 in supercritical geothermal systems does not require a caprock because at the pressure and temperature of these systems, CO2 is denser than supercritical water and, thus, sinks. In light of recent achievements in the drilling of high temperature volcanic areas, such as the Icelandic Deep Drill Project, it deems possible to exploit supercritical reservoirs for CO2 storage combined with simultaneous geothermal energy production where the critical point of water (T = 374°C and p = 21.8 MPa) is exceeded. Our simulations show that CO2 injection is gravity dominated with the reservoir permeability as high as 10 mD and the CO2 plume sinks. Also, if we choose adequate well spacing, CO2 breakthrough can be avoided. Compared with water injection, CO2 injection leads to a smaller area of the cooled region due to the lower heat capacity of CO2, which subsequently lowers the risk of thermally induced seismicity. The cumulative geothermal energy production between water and CO2 is comparable and when considering the benefits of safe long-term CO2 storage, CO2 injection may be a more viable option for supercritical geothermal pressure maintenance.