Laboratory Investigation of Granite Permeability after High-Temperature Exposure

This study experimentally analysed the influence of temperature levels (200, 300, 400, 500, 600, and 800 degrees C) on the permeability of granite samples. At each temperature level, the applied confining pressure was in the range of 10-30 MPa, and the inlet hydraulic pressure varied below the corresponding confining pressure. The results are as follows: (i) With an increase in the temperature level, induced micro-fractures in the granites develop, and the decrement ratios of both the P-wave velocity and the density of the granite increase; (ii) The relationship between the volume flow rate and the pressure gradient is demonstrably linear and fits very well with Darcy's law. The equivalent permeability coefficient shows an increasing trend with the temperature, and it can be best described using the mathematical expression K-0 = A x 1.01(T); (iii) For a given temperature level, as the confining pressure increases, the transmissivity shows a decrease, and the rate of its decrease diminishes gradually.