Modeling of Geothermal Energy Recovery from a Depleted Gas Reservoir: A Case Study

This paper addresses the problem of the geothermal energy generation process in a depleted gas reservoir with a specific enhanced geothermal system, applying CO 2 as an energy transporting medium. Constructed models of the system components are used to perform coupled and dynamic simulation forecasts, taking into account the interdependence of the individual system elements operating in a cyclical fluid flow and the continuous changes in temperature, pressure, and the composition of circulating fluids. The simulation procedure of the geothermal energy generation process is applied to the realistic example of a depleted gas reservoir located in Foresudetic Monocline, Poland. The simulation results are presented in detail and discussed with several conclusions of both case-specific and general characters. Three phases of the energy recovery process can be distinguished, varying in the produced fluid composition and the evolution of the fluid temperature. These phases result in the corresponding behavior of the produced stream power: increasing, stable, and decreasing for the three phases, respectively. Other significant results of the simulation forecasts are also discussed and concluded. In general, the complexity of the obtained results proves the necessity to apply the system’s detailed modeling and simulations to reliably plan and realize a geothermal energy generation project.