Experimental characterization and dependence of rock fracture permeability on 3D stresses

The effectiveness of transmitting underground fluid in fractured rock mass is significantly influenced by stresses. This paper intends to study the hydraulic behavior of rock fractures under 3D stresses. First, a fracture permeability model has been developed for predicting permeability of rough fractures subjected to 3D stresses on the basis of minimum potential energy principle. Then, a series of transient flow tests are conducted on three fractured shale samples. The test results show that pressure response deviates the exponential behavior at early time, thus the late time data is recommended for permeability calculation. The permeability of fractured rocks are related to 3D stresses, specifically, permeability decreases with the increasing of confining pressure. Variation of curve for fracture deformation versus flow time follows the same trend as the curve for differential pressure versus time (Δp-t), indicating that the pressure decay has a principal dependence on fracture deformation. At last, a comparison between with experimental permeability and the proposed model is tackled, which demonstrates that the proposed model is capable of matching the experimental data for 3D stresses.