Effects of seepage flow patterns with different wellbore layout on the heat transfer and power generation performance of enhanced geothermal system

Abstract

Hydraulic fractures provide the conductive channel for geothermal fluid flow and heat transfer for enhanced geothermal reservoir (EGS). The wellbore layout has a significant impact on the performance of EGS. The thermohydraulic-mechanical coupling effect in fractured reservoirs has been described. However, when CO2 is considered as the geothermal fluid, the effect of different seepage flow patterns is neglected. A coupled THM semi-numerical model of fractured reservoir is established by porous medium theory, with three seepage flow patterns, the non-local thermal equilibrium, and the non-Darcy's law. Results show that a thermal short-circuit is easier to generate by spherical seepage flow. The inertial force for CO2 is increased with the permeability. As a result, there is an increase in the intensity of heat transfer and in the rate of heat extraction. The enhanced heat transfer improves the buoyancy effect due to a large density difference, and further accelerates the thermal short-circuit. Re has the most significant effect on geothermal power generation enhancement, followed by geothermal gradient, injection temperature and flow pattern. Meanwhile, the space between the injection and production wells with high conductivity meets the conditions for the formation of planar linear or radial seepage flow for decreasing electrical consumption.