Modeling the Onset of Thermal Short-Circuiting in EGSs with a Coupled THM-Wellbore Approach

Abstract

Thermal short-circuiting significantly undermines the long-term productivity and economic sustainability of Enhanced Geothermal Systems (EGS). This research examines the synergistic physical mechanisms—thermal edge effects, non-isothermal wellbore flow, and thermal destressing—that drive this phenomenon using a coupled Thermo-Hydro-Mechanical-Wellbore (THM-W) framework. The model reveals that an initially uniform reservoir eventually develops preferential flow channels through a self-reinforcing feedback loop. This evolution begins with wellbore friction and thermal edge effects, which induce rock contraction and cooling near central fractures. By the 28-year mark, thermo-mechanical opening becomes the primary flow regulator; central fracture apertures expand from 5 mm to over 7 mm, while permeability escalates from 5×10-11 m2 to 4.06×10-8 m2. This high-conductance path captures a disproportionate 30% of injected fluid, triggering premature thermal breakthrough. Furthermore, while proppants enhance hydraulic conductivity, they also expedite thermal decline. These findings offer a quantitative evaluation of the mechanisms precipitating thermal short-circuiting, providing essential insights for the development of future engineering interventions and mitigation strategies.