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Coupled thermo-hydro-mechanical modeling of hydraulic fracture propagation in hot dry rock.

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Title: Coupled thermo-hydro-mechanical modeling of hydraulic fracture propagation in hot dry rock.
Authors: Meng, Keyu1,2 (AUTHOR), Li, Mengli3 (AUTHOR), Li, Mengyi4 (AUTHOR), Dontsov, Egor5 (AUTHOR), Zhang, Fengshou1,2 (AUTHOR) fengshou.zhang@tongji.edu.cn
Source: Engineering Fracture Mechanics. Jun2026, Vol. 340, pN.PAG-N.PAG. 1p.
Subjects: Hydraulic fracturing, Temperature effect, Crack propagation, Geothermal wells, Effective stress (Soil mechanics), Geothermal engineering, Viscosity
Abstract: • A DEM-based THM model for hydraulic fracturing in hot dry rock to 300 °C was developed. • Temperature, confinement, and viscosity influence fracture and breakdown pressure. • Breakdown pressure drops linearly with temperature, refining predictions. • Greater stress anisotropy shifts control from thermal to confinement effects. Hot dry rock (HDR) is an important geothermal resource whose development relies on hydraulic fracturing to create high-conductivity fracture networks for efficient geothermal energy extraction in Enhanced Geothermal Systems (EGS). In this study, a coupled Thermo-Hydro-Mechanical (THM) discrete element model was developed to investigate the hydraulic fracturing process in HDR. The model incorporates fluid flow, heat transfer, and mechanical deformation to achieve coupled THM processes. After verification under hydro-mechanical (HM), thermo-mechanical (TM), and thermo-hydro (TH) conditions against analytical benchmarks, the model was adopted to examine the effects of temperature (20–300 °C), confining pressure (20–40 MPa), and fluid viscosity (1–100 mPa·s) on fracture propagation. Higher breakdown pressure is more easily achieved under coupled conditions of low temperature, high confining pressure, and high fluid viscosity, whereas complex fracture networks are more readily generated under high-temperature and low-confinement conditions. Temperature plays a key role by weakening the rock matrix and inducing thermal damage zones near the borehole, which enhances fracture complexity but reduces breakdown pressure. Stronger confining pressure increases breakdown pressure and limits fracture complexity, while increasing stress anisotropy shifts fracture control from thermal-stress-dominated to confinement-dominated behavior. Higher-viscosity fluids increase breakdown pressure by delaying fracture propagation and enabling greater energy accumulation. The associated fluid lag reduces tip pressure and inhibits the uniform activation of multiple fractures, thereby limiting fracture complexity and promoting dominant fracture growth. These findings provide numerical support for understanding fracture behavior in high-temperature reservoirs and offer practical guidance for optimizing hydraulic fracturing strategies in EGS development. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:• A DEM-based THM model for hydraulic fracturing in hot dry rock to 300 °C was developed. • Temperature, confinement, and viscosity influence fracture and breakdown pressure. • Breakdown pressure drops linearly with temperature, refining predictions. • Greater stress anisotropy shifts control from thermal to confinement effects. Hot dry rock (HDR) is an important geothermal resource whose development relies on hydraulic fracturing to create high-conductivity fracture networks for efficient geothermal energy extraction in Enhanced Geothermal Systems (EGS). In this study, a coupled Thermo-Hydro-Mechanical (THM) discrete element model was developed to investigate the hydraulic fracturing process in HDR. The model incorporates fluid flow, heat transfer, and mechanical deformation to achieve coupled THM processes. After verification under hydro-mechanical (HM), thermo-mechanical (TM), and thermo-hydro (TH) conditions against analytical benchmarks, the model was adopted to examine the effects of temperature (20–300 °C), confining pressure (20–40 MPa), and fluid viscosity (1–100 mPa·s) on fracture propagation. Higher breakdown pressure is more easily achieved under coupled conditions of low temperature, high confining pressure, and high fluid viscosity, whereas complex fracture networks are more readily generated under high-temperature and low-confinement conditions. Temperature plays a key role by weakening the rock matrix and inducing thermal damage zones near the borehole, which enhances fracture complexity but reduces breakdown pressure. Stronger confining pressure increases breakdown pressure and limits fracture complexity, while increasing stress anisotropy shifts fracture control from thermal-stress-dominated to confinement-dominated behavior. Higher-viscosity fluids increase breakdown pressure by delaying fracture propagation and enabling greater energy accumulation. The associated fluid lag reduces tip pressure and inhibits the uniform activation of multiple fractures, thereby limiting fracture complexity and promoting dominant fracture growth. These findings provide numerical support for understanding fracture behavior in high-temperature reservoirs and offer practical guidance for optimizing hydraulic fracturing strategies in EGS development. [ABSTRACT FROM AUTHOR]
ISSN:00137944
DOI:10.1016/j.engfracmech.2026.112150