In Canada, both Nexen’s Long Lake and Suncor’s Firebag steam-assisted gravity drainage (SAGD) Projects reported existence of intersecting lean zones that behave as thief zones. Thoroughly understanding the effect of lean zones and improving SAGD operations with such heterogeneity are critically important in reducing the disadvantages of lean zones during SAGD production.
The mechanisms of how mobile water affects the SAGD production are thoroughly studied by developing analytical transient solutions. Meanwhile, the effects of the location, thickness, size, and interval distance of lean zones on SAGD are numerically discussed. The relationship between the steam chamber volume and steam-oil ratios is also highlighted. The ten-year history match is performed based on the geological model in the Lone Lake Field. A hybrid cyclic steam stimulation (CSS)/SAGD method is furthermore proposed and studied to overcome the practical problem of low injection pressure due to lean zones.