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Hydrofractured shale reservoirs exhibit a complex hierarchy of heterogeneous structures. Although the importance of hierarchical structures has long been recognised, the full control of scale-dependent heterogeneities on gas production remains ill-defined. We characterize reservoir structural heterogeneity at four hierarchical levels: (1) heterogeneous nanopore structure of the OM (Organic Matrix/Kerogen); (2) heterogeneous micro-structure of the IOM (Inorganic Matrix); (3) discrete structure of the NFNs (Natural Fracture Networks); and (4) discrete structure of the HFs (Hydraulic Fractures). A fractal approach is applied to characterize these internal structural heterogeneities for both the OM and IOM. These characterisations are incorporated into the constitutive relations defining transport within the OM and IOM. NFNs are generated by the Monte Carlo method while HFs are represented by a fractal tree-like network …