Effect of clay content on permeability behavior of argillaceous porous media under stress dependence: A theoretical and experimental work

Prediction of permeability behavior of argillaceous porous media (APM)is a major challenge for science and engineering, despite considerable advances in using both theoretical and experimental means over the last few decades. Specifically, the effect of clay content on stress sensitivity of APM is still an open question. In this paper, laboratory tests are conducted to investigate the effect of clay content on behavior of permeability for artificial argillaceous sandstone samples under stress dependence. Then a corresponding theoretical model for stress dependent permeability of APM based on fractal theory is derived to interpret the experimental results. The predicted results from the developed theoretical model are consistent with those determined by experimental tests, which verifies the developed model. The proposed model can be invoked to effectively study the coupled flow-deformation behavior in APM. The results show that the normalized permeability increases with increasing the power law index, increasing elastic modulus, increasing rock initial porosity, and decreasing clay content at a given effective stress. This work provides a comprehensive experimental and theoretical study on stress-dependent permeability in APM, which is beneficial to study the effect of clay content on permeability behavior of APM under stress dependence. In addition, with this proposed model, we can conduct the estimation of specific parameters (e.g., the structure of pore surface, the fractal dimension of pore, the maximum pore radius, the minimum pore radius, clay content, initial irreducible water saturation, and rock elastic modulus)using inverse modeling approaches.