STEAMFLOODING COLD LAKE OIL-RESERVOIRS THROUGH A BOTTOMWATER ZONE - ASCALED PHYSICAL MODEL STUDY

A series of experiments was conducted in one-eighth of a five-spot-pat tern, high-pressure, scaled physical model to evaluate the potential o f steamflooding oil-sand reservoirs through a bottomwater zone in Cold Lake, Alta. During the experiments, steam was injected into the botto mwater zone at a constant rate until steam break-through occurred at t he production well. The steam injection rate then was reduced to limit steam production. Results demonstrate that the process is influenced by the steam injection flow rate because of the important role played by gravity override. Increasing the steam injection rate beyond an opt imum value results in decreased oil/steam ratios (OSR's) and reduced f inal oil recovery because steam channels to the production well. A del ay in oil production was noticed in all experiments. A moving-heat-sou rce, gravity-override, analytical model was used to investigate the me chanisms of reservoir heating in the presence of steam-gravity overrid e. In addition, the thermal efficiency of the process, determined from the experiments and extrapolated to field conditions, was compared wi th predictions from Prats' thermal efficiency model. Prats' model pred icted the measured thermal efficiency reasonably well at lower injecti on rates. As the injection rate increased, however, larger differences between Prats' model and the experiments were noticed.