Towards numerical modelling of THMC coupled processes in fractured geothermal reservoirs

Abstract

Sustainable and successful energy recovery from deep geothermal reservoirs requires a comprehensive understanding of how different local scale physical and chemical processes affect the short and long term heat transport. Geothermal aquifers may be utilized for storing CO2 through dissolution of CO2 in the return (cold) water stream of geothermal doublets. The safety and performance of operations highly depends on reservoir physical, thermal, and compositional properties, which may change following cooled water injection and potential reactions. Yet, the emergent behaviour of the system due to the interaction of thermal, flow, mechanical and chemical processes is not fully understood. We present a new framework permitting coupled simulation of Thermal-Hydro-Mechanical (THM) processes in geothermal reservoirs. The approach simultaneously couples non-isothermal laminar flow through fractures and Darcy flow through the rock matrix with thermoporoelastic deformation. This framework easily lend itself for modelling reactive transport in fractured geothermal reservoirs. The coupled THM model is validated against several benchmark examples and employed to study the effect of THM processes on energy production in a geothermal doublet.