An analytical approach is introduced, for the first time, to evaluate the effect of confinement and well interference on SAGD process and achieve a better understanding of the situation. In this stage of SAGD, adjacent chambers interfere, the effective height for oil drainage decreases and heat loss rate decreases or in a conservative design remains constant. The objectives are to predict; oil production rate, steam injection rate, thermal efficiency, steam chamber velocity, unsteady temperature profile, heat distribution, and Cumulative Steam-Oil Ratio (CSOR). In this approach, heat transfer is coupled with fluid flow. The governing equations are; Darcy's law, volumetric balance, heat conduction, constitutive equations indicating the temperature dependence of some physical properties. The model is developed based on a moving boundary problem.