Transcripción del resumen del autor: Approximately 80% of the 173 billion barrels of recoverable crude bitumen in the Athabasca oil sands require in-situ recovery due to the depth of burial. Steam-Assisted Gravity Drainage (SAGD) has become the preferred in situ recovery process for producing Athabasca oil sands reservoirs. It is well known that oil sands reservoirs are heterogeneous with respect to porosity, permeability, phase saturations, and fluid composition. A large-scale heterogeneity that has been encountered in SAGD operations is top and bottom water thief zones. However, evidence of intraformationalwaterzones has also been found: seismic, log, and core analysis suggest that these waterzones can exist as both isolated pockets and extensive connected regions within the oil column. The effect of these high water saturation zones on the SAGD process is largely unexplored. In this research, detailed thermal reservoir simulation is used to study the movement of water during SAGD operations in reservoirs with several intraformationalwaterzone configurations. The effect of waterzone extent, connectivity, saturation and operating conditions on water movement and SAGDperformance is examined. Fluid migration out of the reservoir is found to be relatively small, with ‘oil plugs’ effectively sealing waterzones in front of the growing steam chamber. However, waterzones are found to have a significant effect on production. The inclusion of water channels led to an average drop in production of 73% while waterzones in the form of interconnected nodes led to a 12% reduction. This indicates that the spatial distribution of waterzones largely determines the effect on SAGDperformance. The variation in production is the result of heterogeneous steam chamber growth that leaves large areas of the reservoir unswept. This appears to be largely due to the influence of waterzones on near wellbore pressure distributions, particularly at early times. By acting as either ‘pressure sinks’ or ‘pressure transmitters’ waterzones are able to both ‘seed’ and suppress steam chamber growth.