Evolution of gas seepage properties in shale fractures under different confining pressure and temperature conditions

Abstract

This study investigated the impact of temperature and confining pressure on the seepage behavior of rock fractures. Through a combination of theoretical analysis and numerical simulations, a novel coupling model that integrates the interdependent effects of confining pressure, temperature, and gas seepage in fractures has been proposed and validated. The coupling nature of these factors is characterized by their synergistic interactions: confining pressure directly influences the fracture aperture, which in turn affects fluid flow dynamics, while temperature alters the gas viscosity and further modifying the seepage behavior. The results indicate: An increase in confining pressure diminishes the fracture mechanical aperture, leading to enhanced biased fluidity and inertia forces. When the confining pressure rises from 0.565 to 0.916 MPa, biased fluidity escalates by 19 %, seepage resistance surges by 44 %, and the permeability coefficient diminishes by 23 %–27 %. When the temperature rises from 293.15 to 373.15 K, seepage resistance to augment by 20 %, and the permeability coefficient to decline by 14 %–19 %. The proposed theoretical model, which uniquely accounts for the coupled thermo-hydro-mechanical interactions and not only offers insights into the interactions between geological conditions and fluid mechanics in fractured shale environments but also provides a new ideas for the improvement of existing models.