Temperature Dependence of the Permeability of Sandstone Under Loading and Unloading Conditions of Confining Pressure

Rock permeability is a key parameter in evaluating the CO2 storage capacity and injectivity in geologic CO2 sequestration projects. To investigate the influences of confining pressure and testing temperature on rock permeability, seepage tests were carried out on four cylindrical sandstone specimens using a newly developed triaxial permeability measurement system. In this study, the confining pressure was loaded and unloaded stepwise between 10 and 30 MPa at different temperatures (25-90 degrees C). The experimental results showed that as the effective confining pressure increased in the loading process, sandstone permeability decreased nonlinearly. As the effective confining pressure decreased in the unloading process, permeability increased nonlinearly. Elevated temperature decreased the sandstone permeability, and the percentage reduction in permeability decreased with increasing temperature. Micropore space closure and thermal expansion were evidence of the permeability changes as the confining pressure and testing temperature were varied. The experimental results obtained in the seepage tests under the different confining pressures and elevated testing temperatures provide a reference for evaluating rock permeability in underground engineering.

Automated summary

The study found that as the effective confining pressure increased, sandstone permeability decreased nonlinearly, while as the effective confining pressure decreased, permeability increased nonlinearly. Elevated temperature decreased sandstone permeability, however, the reduction in permeability decreased with increasing temperature.