Mechanism and method for efficient geothermal energy development in deeply-mining activated reservoir
MA Dan
YAN Jinghong
LI Qiang
GAO Xuefeng
Abstract：Deep coal mines are associated with abundant karst geothermal resources.However,their naturally low permeability significantly constrains the efficient exploitation of these re-sources.This study proposes utilizing the pressure-relief zone formed in the floor strata after longwall mining to activate fracture apertures and achieve self-enhanced permeability in the reservoir,offering a promising new pathway for efficient geothermal development.For this purpose,a thermal-hydraulic-mechanical(THM)fully coupled model was established specific-ally for mining-induced reservoir activation for geothermal extraction.The model characterized the distribution of fracture aperture and permeability under mining influence,revealed the dy-namic evolution of geothermal production efficiency during the activation process,clarified the mechanism behind enhanced heat extraction in the activated reservoir,and proposed a method for synergistic and efficient co-development of deep coal and geothermal energy.The results indicate that mining-induced effects reduce the normal stress on fractures in the goaf floor,triggering shear dilation or tensile opening effects that significantly increase fracture apertures,leading to the formation of a funnel-shaped high-permeability zone in the floor reservoir.Min-ing activities enhance the average flow velocity within the channels,expand the effective flow range,and improve the heat transfer efficiency during cold fluid reinjection.As the mining dis-tance increases,both reservoir permeability and heat extraction efficiency improve rapidly ini-tially,followed by a gradual slowdown in the rate of enhancement.A"mining-first,heat pro-duction-follows"approach for coordinated coal-geothermal development is proposed,wherein high-permeability zones in the floor strata are delineated following mining face advancement,followed by the deployment of wells along its major axis to achieve efficient geothermal re-source extraction.This study provides theoretical support for the integrated development of coal and geothermal energy and offers a novel approach for the enhancement of low-permeabili-ty geothermal reservoirs.
Keywords：mining-induced activationgeothermal developmentefficient developmentgeo-thermal development methods
Publication Date：2025-11-30
Online Publishing Date：2026-01-09(First online date of this platform, not the publication date of the document)
Pages：12( 1447-1458 )