Simulation study of supercritical carbon dioxide jet fracturing for carbonate geothermal reservoir based on fluid-thermo-mechanical coupling model

Geothermal energy is a kind of renewable, sustainable and clean energy resource. Geothermal energy is abundant in carbonate reservoirs. However, low matrix permeability limits its exploitation. The supercritical carbon dioxide (SC–CO2) jet fracturing is expected to efficiently stimulate the carbonate geothermal reservoirs and achieve the storage of CO2 simultaneously. In this paper, we established a transient seepage and fluid-thermo-mechanical coupled model to analyze the impact performance of SC-CO2 jet fracturing. The mesh-based parallel code coupling interface was employed to couple the fluid and solid domains by exchanging the data through the mesh interface. The physical properties change of SC-CO2 with temperature were considered in the numerical model. Results showed that SC-CO2 jet fracturing is superior to water-jet fracturing with respect to jetting velocity, particle trajectory and penetrability. Besides, stress distribution on the carbonate rock showed that the tensile and shear failure would more easily occur by SC-CO2 jet than that by water jet. Moreover, pressure and temperature control the jet field and seepage field of SC-CO2 simultaneously. Increasing the jet temperature can effectively enhance the impingement effect and seepage process by decreasing the viscosity and density of SC-CO2. The key findings are expected to provide a theoretical basis and design reference for applying SC-CO2 jet fracturing in carbonate geothermal reservoirs.