Effect of mineralogy on frictional strength and stability of shale fractures during slip

We report experimental research on frictional strength and stability properties of shale fractures during slip. Longmaxi shale, Green River shale and Marcellus shale are selected for constant-velocity and velocity-stepping fracture shear experiments. Combing with theoretical analysis, micro controlling mechanism of mineralogy on frictional strength and stability properties of shale fractures is discussed. Results indicate that the fracture friction-stability relationship is largely affected by shale mineralogy. Frictional strength of shale fractures increases when tectosilicate content increases and phyllosilicate content decreases; during velocity-stepping experiments, three kinds of shale show velocity-strengthening behavior, which means an aseismic creep tends to occur; with the increase content of tectosilicate, shale fractures tend to have seismic slip while with the increase of phyllosilicate content, stable aseismic creep happens.