[Paper Review] A Numerical Study of Thermal-Hydraulic-Mechanical (THM) Simulation with the Application of Thermal Recovery in Fractured Shale Gas Reservoirs

HanYi Wang|arXiv (Cornell University)|Nov 2, 2017

Hydrocarbon exploration and reservoir analysis1 references3 citations

TL;DR

This study presents a fully coupled thermal-hydraulic-mechanical (THM) numerical model for fractured shale gas reservoirs, integrating gas adsorption, real gas behavior, nanoscale flow, and geomechanics. Results show that elevated temperature significantly enhances gas desorption and flow capacity by altering adsorption characteristics, offering a viable thermal recovery pathway for low-permeability shale formations.

ABSTRACT

We presented a general multi-physics model for shale gas flow in fractured systems, first the first time, with fully coupled thermal-hydraulic-mechanical (THM) properties. The impact of gas adsorption, real gas properties, gas flow in nano-scale pore space and geomechanics effects on total gas flow capacity are investigated. We also showed that by elevating shale rock temperature, the characteristic of gas adsorption behavior can be substantially altered.

Motivation & Objective

• To develop a comprehensive multi-physics model integrating thermal, hydraulic, and mechanical effects in fractured shale gas reservoirs.
• To investigate the influence of gas adsorption, real gas properties, and nanoscale flow on total gas production capacity.
• To evaluate the impact of temperature elevation on shale gas desorption behavior and reservoir performance.
• To assess the feasibility of thermal recovery as an enhanced extraction method in low-permeability shale formations.

Proposed method

• A fully coupled THM model is formulated to simulate heat transfer, fluid flow, and rock deformation in fractured shale systems.
• The model incorporates real gas law for pressure-dependent gas viscosity and compressibility.
• Adsorption is modeled using the Langmuir isotherm, with temperature-dependent Langmuir parameters to reflect thermal effects.
• Nanoscale flow in shale matrix is simulated using Knudsen diffusion and slip flow corrections for transition regime.
• Geomechanical effects are included through stress-dependent permeability and matrix deformation.
• The model is solved numerically using finite element methods with iterative coupling of thermal, hydraulic, and mechanical sub-problems.

Experimental results

Research questions

• RQ1 How does temperature elevation affect gas desorption capacity in shale gas reservoirs?
• RQ2 To what extent do nanoscale flow mechanisms and real gas behavior influence total gas production in fractured shales?
• RQ3 How do coupled thermal, hydraulic, and mechanical processes alter reservoir permeability and flow capacity?
• RQ4 Can thermal stimulation significantly enhance gas recovery in low-permeability fractured shale formations?

Key findings

• Elevating shale rock temperature substantially alters gas adsorption behavior, increasing desorption and enhancing gas availability for flow.
• The inclusion of real gas effects and nanoscale flow mechanisms leads to higher predicted gas production rates compared to idealized models.
• Thermal expansion and stress changes due to heating modify fracture aperture and matrix permeability, influencing fluid transport.
• Coupled THM effects result in non-linear responses in gas flow capacity, with peak enhancement observed at intermediate temperature increases.
• The model demonstrates that thermal recovery can significantly improve gas production in tight, fractured shale systems by overcoming mass transfer limitations.
• Temperature-dependent adsorption isotherms show a marked shift in gas uptake capacity, validating thermal stimulation as a viable recovery strategy.