Thermo-hydro-mechanical modeling of an Enhanced geothermal system in a fractured reservoir using CO2 as heat transmission fluid- A sensitivity investigation

Abstract: Geothermal energy has the potential to support direct heat usage and electricity generation at low carbon footprint. Using CO2 as heat transfer fluid can allow us to achieve negative carbon energy solution. In this study, geothermal energy extraction potential from a discretely fractured reservoir using CO2 is assessed. Geothermal energy extraction process is a coupled thermo-hydro-mechanical (THM) mechanism and the geomechanical stresses involves thermoelasticity and poroelasticity. This study demonstrates a fully coupled THM mechanism for enhanced geothermal system (EGS) operations. A large number of parameters are involved in the THM mechanism and therefore, it becomes difficult to assess the key operating parameter to have better operating efficiency. We identified 22 input parameters that controls the THM mechanism. Therefore, under the Horizon 2020 project: Multidisciplinary and multi-contact demonstration of EGS exploration and Exploitation Techniques and potentials (H2020 MEET) we have performed sensitivity analysis to investigate the relative importance of these parameters that concentrates on three key objective parameters: thermal breakthrough time, mass flux and overall energy recovery. The important parameters controlling these three objective parameters are matrix permeability and fracture aperture whereas wellbore radius has an impact on mass flux and total energy recovery.