There has been a keen interest during the last decade in the application of the steam assisted gravity drainage (SAGD) process as a recovery strategy for oil sands and heavy oil reservoirs. The recent success of field pilot demonstrations in Alberta and Saskatchewan has further accentuated the need to understand process mechanisms and determine techniques to accelerate recovery rates for improving economics. This paper provides an in depth analysis of the SAGD process using numerical and experimental tools. Two-dimensional scaled gravity drainage experiments, designed to represent heavy/extra heavy oil reservoirs, were used to calibrate the thermal reservoir simulator STARS. Visual observations of the development of the steam chamber (gravity cell) were made during the experiments and compared to numerical model predictions. The results obtained provided insight into the effect of key parameters such as permeability, pressure difference between the wells, capillary pressures and heat losses on process performance. A detailed study on the effect of permeability on source/sink simulation of the SAGD process demonstrated the importance of the initialization or transient phase of the process. The duration of the initialization phase increased as the permeability decreased, indicating that this phase occupied an increasingly significant portion of the entire drainage process as permeability decreased. The sensitivity of the validated numerical model to a number of key parameters required for numerical simulation of the process are highlighted in the paper. The effort is intended as a precursor to modeling field scale gravity drainage processes. The ultimate application of the work is in thermal heavy oil recovery operations using steam assisted gravity drainage.

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