Abstract

As efforts are made to exploit and recover bitumen resources in Canada, challenges presented by increasingly more complex reservoirs in the Athabasca area continue to pose a challenge to the application of the Steam-Assisted Gravity Drainage (SAGD) technology. Several studies have been done to investigate the impact of heterogeneities/complexities such as shale barriers, lean zones, top and bottom water on the performance of the SAGD process. However, the literature is deficient especially in point bar deposits with top water zones. This study examines by using thermal reservoir simulation the impact on the SAGD performance in a point bar deposit reservoir where an overlying top water and an inclined heterolitic strata (IHS) is present. The results show that where the top water is unconfined and the steam injection pressure is higher (4,000 kPa) than that of the top water zone, there is a huge loss in thermal energy but the top water does not inhibit the steam chamber development. But when compared to a relatively lower steam injection pressure (1,800 kPa), the top water continuously drains into the reservoir and reduces the size of the steam chamber. The confined top water case behaves very similar to a point bar reservoir without top water at high steam injection pressures and when compared to a relatively lower steam injection pressure, the top water does not significantly impact the SAGD performance. The IHS zone may constitute some nuisance to the steam chamber development but also helps to delay the drainage of the top water into the basal sand when steam is injected underbalance. Finally, under proper steam injection pressure condition, the top water production can be considerably delayed.

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