Study of the quantitative effect of the depositional layering tendency of inclusions on the elastic anisotropy of shale based on two-step homogenization

Shale anisotropy is related to numerous small-scale factors, including the transverse isotropy of clay particles, clay shape aspect ratio, shape preference orientation, pore/crack alignment, infilling materials and the depositional distribution and shape aspect ratio of inclusion minerals. Although a depositional layering tendency of inclusions due to sedimentation has been observed, few studies of its effect on shale anisotropy have been carried out. In this work, the effect of the depositional layering tendency of inclusions on the elastic anisotropy of shale is quantitatively analysed along with three other factors (i.e. the inclusion fraction, the orientation dependence of clay elastic properties, where `oriented' refers to transverse isotropic clay and `non-oriented' refers to isotropic clay, and the clay elastic moduli) based on analysis of variance and the two-step homogenization of shale by assuming that shale is a composite of clay and inclusions. The results show that the depositional layering tendency of inclusions of this type of shale has a relatively limited effect on the elastic anisotropy of intact shale, while the orientation dependence of the elastic properties of the clay has a predominant influence.