Evolution of permeability and heterogeneity in flow paths under different high temperatures and high confining pressures

With the continuous advancement of deep oil and gas resource development, the evolution of permeability characteristics for sandstone under high temperature and high-pressure conditions has become critical scientific issues urgently to be addressed. This study conducted permeability tests on sandstone specimens with different inlet pressures, confining pressures, and temperatures, combined with COMSOL Multiphysics multi-field coupling numerical simulations. Applying thermal-hydraulic-mechanical coupling analysis methods, the variation characteristics and evolution mechanisms of sandstone permeability were investigated. The experimental results show that the permeability of sandstones exhibits significant nonlinear decreasing characteristics under temperature-confining pressure coupling effects. When temperature increases from 20 to 95 °C, the reduction of flow rate reaches 78.1% and 86.8% under the confining pressures of 10 and 60 MPa, respectively. The influence of confining pressure on permeability is mainly concentrated in the stage of low confining pressure due to the pore compression effects. The heterogeneous numerical model based on the Weibull distribution effectively reproduced the experimental results. The numerical simulation results reveal that the multi-field coupling mechanisms of sandstone permeability evolution: confining pressure directly alters pore structures through mechanical compression and serves as the dominant factor controlling permeability performance; temperature regulates pore channels through thermal expansion effects while simultaneously affecting fluid property parameters. When confining pressure increases from 10 to 60 MPa, the maximum flow rate attenuation reaches one order of magnitude, far exceeding the influence of temperature effects. These research findings provide important theoretical foundation and technical support for deep oil and gas reservoir development.