Abstract: Shape factor is required in modeling naturally fractured reservoirs represented by double porosity theory. The function of shape factor is to define the leakage term between the matrix block and fracture conduits. Different geometric assumption of the double porosity medium resulted in different shape factors and consequently the leakage term. The influence of various shape factors based on different geometric assumptions on their matrix-fracture transfer rate has been studied in this study. Comparison of different shape factor performance is accomplished via the dimensionless pressure and time. This study proposed a new relation that measures the impact of different shape factor in the consequence flow rate in fractured reservoir. It was discovered that higher value of shape factor contributes to higher rate of change of flow rate. This correlation can aid in deciding the appropriate shape factor for modeling double porosity medium.