Assessing the impact of fracture properties and wellbore configuration on the energy extraction from hot dry rock

Future energy development relies on the use of alternative energy sources such as exploitation of deep geothermal energy from Hot Dry Rock (HDR). HDR reservoirs are considered strategical because of the great amounts of heat stored in deep basement. Here, a numerical model considering a discrete fracture network and data from the Soultz-Sous-Forets HDR reservoir (France) was developed. The model setup consists of injection and extraction wells with two-phase circulation fluid (water). Flow rate, permeability, distance from the injection well, and fracture aperture were considered in the analysis. Results indicate that thermal decline is mostly influenced by the permeability of the fractured medium and wellbore configuration. Marginal increments in permeability caused noticeable decrements in temperature in a short lifespan of about 10 years. A simulation of the current scenario shows that sustainable heat extraction for the purpose of electricity generation is achieved for a lifespan of 30 years. The results of this study emphasize that permeability is a critical parameter to be addressed during field investigation and conceptualization of a HRD reservoir; it also provides a better understanding of the viability of deep geothermal projects.