Numerical reservoir simulations have successfully been used for performance analysis of several commercial steam assisted gravity drainage (SAGD) heavy oil recovery projects. The inherently complex calculations involving mass and energy balances, along with consideration for advanced geomechanics, culminate in a strong time limitation for field scale simulations of SAGD processes. As a result, significantly homogeneous gridding has traditionally been used for downwell directions, with grids sizes sometimes exceeding 100 m for three dimensional simulations of SAGD. This represents a compromise which requires further quantitative analysis to clearly understand the implications on uniform steam chamber development and the accuracy of performance predictions. At this point, most simulations are not capable of predicting realistic field performance, especially in the downwell direction, of a given reservoir since grid resolution is poor. In this study, a full field reservoir model representative of a McMurray reservoir is used to analyze the implications of longitudinal grid homogeneity on the propagation of a SAGD steam chamber. In addition, a novel use of flowing steam quality plots to visualize steam migrations and characterize heat transfer during SAGD is presented. The results illustrate the requirements on grid block dimensions necessary to resolve heterogeneities and accurately represent physical phenomena such as flow and heat transfer. The findings of this work provide useful guidelines and have implications for future design and performance analysis of SAGD projects using numerical reservoir simulations.

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