Numerical Simulation of Fluid Flow and Heat Transfer in Hot Rocks with Single Fracture Considering THM Coupling Processes

Abstract

The geothermal heat production from Enhanced Geothermal System (EGS) is influenced by complex thermal-hydraulic-mechanical (THM) coupling process, it is necessary to consider THM coupling effects on utilization efficiency and production performance of EGS. Based on local thermal non-equilibrium theory, a mathematical model incorporating THM coupling processes is established and rough fracture surface is generated based on fractal theory, to investigate the heat extraction performance in EGS with the consideration of fracture heterogeneity. An ideal three dimensional geothermal doublet numerical model is constructed to study the effects of thermal stress and nonhomogeneous aperture distribution on fluid flow pattern and heat transfer. The influence of match relationship between well pattern and fracture aperture distribution field on heat performance is evaluated through two index, average outlet temperature and thermal recovery. The results indicate that under the effects of aperture heterogeneity and thermal stress, the flow channeling phenomenon and early thermal breakthrough is occurred which makes the heat extraction response worse. As for aperture heterogeneity existed in fractured rocks, the injection and production wells should be arranged in vertical direction of high permeability zone to maintain longer heat mining time and improve thermal recovery.