Multiple transverse hydraulic fractures are created simultaneously in each stage for economically viable production of hydrocarbons in shales. The spacing between fractures is an important component to consider when developing an optimum stimulation design. Another important aspect to consider,that is often overlooked,is the anisotropy of mechanical properties inherent in shales. This study aims to provide an insight into the controlling effects of fracture spacing and different levels of rock property anisotropy on the fracture aperture during simultaneous fracture initiation and propagation. Multiple fracture propagation is simulated using 3-Dimensional [3D] finite element models [FEM]. All simulations in this study include simultaneous propagation of four fractures in pre-defined planes using cohesive elements in a linear elastic medium. Numerous FEMs with varying spacing between fractures and varying levels of anisotropy are generated to analyze the effect of spacing and rock anisotropy on the fracture apertures of the edge fractures and center fractures. The multi-fracture propagation model used in this study is capable of showing the isolated influence of each parameter tested. The results show that there is a significant effect on the fracture widths of center and edge fractures across the entire range of fracture spacing considered in the study. The center fractures are more sensitive to changes in fracture spacing and changes in elastic moduli.