An evaluation index for the fracturing effect in shale based on laboratory testing

It is clear that evaluating the fracturing effect with laboratory tests can shed some light on designing fracturing programs for shale gas exploitation. To evaluate the fracturing effect quantitatively, a series of uniaxial cyclic loading tests on shale were conducted. Based on the experimental results, a damage variable derived from the total axial strains of the loading–unloading cycles was established and introduced into a damage evolution equation to analyze damage evolution in the shale. In the end, a new index for evaluating the fracturing effect, \(C_{AN} '\), was proposed. The results show that \(C_{AN} '\) has a positive correlation with fracture complexity and can be regarded as an effective index to evaluate fracture networks in shale using laboratory tests. In addition, this study demonstrates that the fracturing effect is also related to the angle between the direction in which the load is applied and the shale’s bedding plane. This can provide a useful reference for shale gas exploitation.