Abstract: This paper presents an improved model for predicting performance in steam injection wells,which incorporates a downward two-phase flow correlationspresented by Mukherjee and Brill(1985) and account for flow direction and wall inclination angle.It can be used for predicting performance in horizontal steam injection wells that ara developing.The fundamental differential equation in the model is solved numerically by using a fourth-order Runge-Kutta method in which the choice of the start position is arbitrary,it is convenient to take into account the coordination between wellbore and injection layer.

Key words: thick oil production, well performance, well temperature, heat transfer, performance model, numerical model