Gas production from tight gas sands is vital for developing secure unconventional sources of energy. The porous media considered in this paper belong to tight gas reservoirs characterized by extremely low permeability (range of microdarcies) and low porosity (less than 7%) matrix. The transient, three dimensional, two-phase numerical model is presented for simulating the simultaneous gas and water flow through tight gas sand. The solved continuity and momentum equations treat both fluids as incompressible and immiscible. Darcy's and nondarcy's laws were incorporated into the equations to couple them by a fluid transfer term which depends on the potential difference between different specified physical domains. Also, the model accounted for the effect of capillary pressure and relative permeability. The numerical solution was obtained using the modified CFX-Flow3D code. Finite volume approach was used to discretize the equations. The set of discretized and linearized equations were solved using the inter-phase slip algorithm (IPSA) method. The simulation was applied to some obtained results in the laboratory experiments and predicted two-phase flow behavior. Calculated two-phase flow rates reflect the sensitivity of fluid flow to gas and liquid permeability in tight gas sand. The calculated flow behavior agrees reasonably well with experimental drainage, imbibition and two-phase flow behaviors.

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