Numerical simulation of the injection of a CO 2 saturated solution in a limestone sample

Abstract : The CO2-DISSOLVED project [1] proposes to assess the feasibility of a novel CO2 injection strategy in deep saline aquifers, combining injection of dissolved CO2 and recovery of the geothermal heat from the extracted brine. This approach relies on the geothermal doublet technology (commonly used in the Paris Basin, France), where the warm water is extracted at the production well and the cooled brine re-injected in the same aquifer via a second well (injection well). The amount of CO2 that can be injected in the geothermal aquifer is physically limited by CO2 solubility in brine. Injecting CO2-rich acidified water is expected to induce an enhanced reactivity at the immediate vicinity of the injection well, particularly in presence of carbonated minerals. Similarly, acidified water will be much more aggressive for the well casing and cement than standard cold brine in classical geothermal doublets. In order to improve our knowledge on these aspects a dedicated experimental facility, the MIRAGES-2 experimental device designed by GeoRessources [2] was used. MIRAGES-2 is designed for injection of a CO2-rich aqueous solution in an injection well at the 1/20th scale. The well is made of a steel tube that is fixed to the core plug with a class G Portland cement. Well materials (cement and steel) and reservoir rocks (limestone) are used to reproduce elements and interfaces present in real conditions.