An experimental study on permeability of sandstone with different shale contents under 3-D stress conditions

In order to examine the difference in permeability and mechanical properties of sandstones in the three direction stress state, the permeability tests are carried out on shale contents of 4%, 15%, 24% and 31%. The research results show that the strength and elastic modulus of sandstones decrease with the increasing clay cement, and decrease with the increasing confining pressure, and the internal friction angle and cohesive force decrease with the increasing clay content. Permeability with increasing stress decreases first and then increases again slightly in the overall trend under the same confining pressure and clay contents, and the permeability coefficient in the peak stresses near the maximum. The permeability coefficient decreases linearly with the increasing contents of the cement under the same confining pressure and the partial stress. The permeability of sandstones decreases with the increasing confining pressure. Based on the experimental results, a comprehensive model of sandstone permeability considering confining pressure, porosity and shale content is obtained. The rationality of the model is verified by the comparison of the theoretical and experimental data.