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

Abstract

Geothermal energy has the potential to support direct heat usage and electricity generation at a low carbon footprint. Using carbon dioxide (CO2) as a heat transfer fluid can allow us to achieve a negative carbon energy solution. This study assess the geothermal energy extraction potential from a discretely fractured reservoir using CO2. The geothermal energy extraction process is a coupled thermo-hydro-mechanical (THM) mechanism, and the geomechanical stresses involve 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 parameters to have better-operating efficiency. We identified 22 input parameters that control the THM mechanism. Therefore, a sensitivity analysis is performed 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. All the parameters are ranked in order of their importance during an EGS operation.