Multiphase relative permeability is a key parameter in reservoir simulation. Typically, end-point based correlations are employed in order to obtain such curves for reservoir simulation purposes. However, those correlations are not capable of capturing micro-scale physical phenomenon which can significantly affect flow pattern at larger scales. Consequently, it is necessary to obtain a scale-up methodology in order to transfer the micro-scale physics to reservoir-scale. The objective of this research is developing a scale up procedure which can be applied to multi-phase flow properties obtained by micro-scale flow simulation to compute the equivalent macro-scale and core-scale flow properties having the micro-scale flow properties. Two different sets of media are employed: media representing unconsolidated oil sands and media based on experimental data obtained from the Mesaverde formation located in the Poweder River Basin. The former is used for validating the scale up methodology since not all the required information is available in the experimental data set. Pore scale network modelling is used for calculating micro-scale multi-phase flow properties such as porosity, and absolute and relative permeability. Then the generated subsegments are populated in space to reconstruct the macro scale medium. Flow properties of such medium are then obtained by network modelling and the proposed scale-up methodology and the results are compared. Furthermore, macro-scale media are distributed in space in layers and stacks of increasing and decreasing permeability to form a core-level medium. Single and multi-phase flow properties are then calculated by applying a pressure drop across the core. Permeability and relative permeability curves are calculated using the combination of mass balance, equation of state, and Darcy equation assuming steady-state flow while capillary pressure curve is obtained using the modified Leverett-J function procedure used in micro-to-macro scale up section. Results show good agreement between the expected and calculated properties for both unconsolidated and consolidated media. Finally, physical behavior observed at micro and macro scale is transferred to the core scale.