Experimental study on the mechanism of water affecting the permeability characteristics of sandstone

Abstract

The permeability characteristics of sandstone are of great importance for un-conventional natural gas extraction, CO2 geological storage, coal mine gas safety, etc. Under the influence of tectonic stress and mining-induced stress, the evolution of permeability becomes exceptionally complex. A number of studies have focused on the evolution of permeability under different stress paths, ignoring the effect of water on sandstone permeability. The permeability evolution of sandstone in dry and saturated states under high and low surrounding pressures was investigated by triaxial tests. The results show that the triaxial compressive strength of the specimen significantly decreases under saturated conditions. Specifically, the triaxial compressive strength decreases by 27.12% and 10.52% under low and high confining pressure, respectively. Compared to the dry specimen, the permeability of the saturated specimen significantly decreases at all stages of loading, the initial permeability of the saturated specimen is decreased by 92.09% and 56.25% at low and high confining pressure, respectively. The S&D model was matched with the test data, an excellent goodness of fit was obtained in the elastic and plastic phase, and the mechanism of water affecting sandstone permeability was analyzed.