Experimental study of gas permeability evolution in tight sandstone with damage and cracking along various stress loading paths

The evolution of permeability of tight sandstone was investigated under different stress states. A series of hydrostatic compression, triaxial compression, and lateral decompression tests with cooccurrence gas permeability measurement were performed on the tight sandstone samples drilled from an underground abandoned mine in Huainan city of China. The deformation and permeability evolution characteristics under different loading paths were analyzed. Furthermore, the key factors controlling changes in permeability were identified, and the mechanism of permeability evolution under different stress states was discussed. Finally, a mathematic model was proposed to describe the evolution of permeability with volumetric strain under triaxial compression. It shows that permeability decreases continuously under hydrostatic compression, while first decreases and then increases under triaxial compression and remains unchanged under lateral decompression. The stress-induced volumetric strain governs the permeability change, and the proposed model can accurately describe the relationship between permeability and volumetric strain under triaxial compression. The results provide a basis for both theoretical and experimental analyses of the sealing ability against permeation of tight rocks.