Experimental investigation of the influence of differential stress, confining pressure and strain on aquifer sandstone permeability

The influence of confining pressure, differential stress and strain on the permeability of aquifer sandstone was investigated in this study. Experimentally acquired data relating differential stress–axial strain, permeability–axial strain and volumetric strain–axial strain from three stress paths were analysed. Test results showed that under stress path 1, where confining pressure remains constant and axial stress increases or decreases, the permeability increases regardless of the increase or decrease in axial stress. The permeability increment is relatively small only when axial stress increases. Under stress path 2, where axial stress remains constant after peak stress and confining pressure increases or decreases, the permeability and confining pressure are in an inverse relationship. Under stress path 3, where axial stress and confining pressure either increase or decrease, the permeability of sandstone sample decreases when both of these two components increased. The general correlations between permeability and volumetric strain in sandstone sample under three stress paths follow an exponential law. However, the correlation between permeability and volumetric strain under stress path 3 is much weaker than that under the other two paths. The Chilingar model can well fit the permeability–volume strain relationship under stress paths 1 and 2, especially in the post-peak region.