Abstract: Natural gas production from ultra-low permeability unconventional gas formations relies on natural fracture networks and the hydraulic fractures to provide the flow pathways from the formation to the well. The double-porosity model, a flow domain is composed of matrix blocks with low permeability, embedded in a network of interconnected fractures, is commonly used to simulate naturally fractured fracture. Global flow and transport in the formation occur only through the fracture system, conceptualized as an effective continuum. An important constant factor called shape factor is applied to simulate the matrix-fracture exchange term. However, most shape factors are borrowed directly from those used in conventional reservoir simulation, which may not be applicable in unconventional gas reservoir simulation. In this paper, geometric shape factors are derived considering the physics of gas slippage and the sorption term with the assumption of Lim and Aziz, and a fine grid discretization of two-/three-dimensional system are run to examine the accuracy of the new-derived shape factors. The results indicate the shape factors derived in this paper highly increase the accuracy.