The Burnt Lake Oil Sand Lease is located about 300 km northeast of Edmonton. The lease is estimated to contain 330 million m3 of bitumen in place in the Clearwater oil sands formation. Cold production was tested in the lease to recovery 11–12 °API crude bitumen between 1990 and 1993.
Three pairs of SAGD operation began in April of 1997 after three months of circulation. Many interesting characteristics were identified in the injection and production history. During the first year of operation, pressure and oil production rates decreased when steam injection rates were reduced. After the second year of operation, oil production rates responded inversely to steam injection rates. Oil rates were reduced when steam rates were increased and oil rates increased when steam rates were reduced. Declines in oil rates were relatively slow over the entire operation period. When the steam injection was stopped for about five months after five years of operation, the operation pressure and oil production rates were gradually reduced during this period.
Many other unexpected trends were also observed. All these features were consistently seen in all three pairs. This paper presents these behaviours in detail. A simulation study of nine years of performance of Pair 1 was conducted to understand these characteristics. The history match demonstrated that oil production was achieved by two different mechanisms: one was expansion of the steam chamber and the other was drainage of oil from the layer above the steam chamber. Many unexpected performances were the result of the combination of these two recovery mechanisms.
Three pairs of SAGD wells began production in April of 1997 after three month of circulation. Cumulative performances to December 31, 2005 were: (Table available in full paper)
Steam injection rates, oil production rates, and operation pressure of these SAGD pairs are shown in Figures 1 to 3. Well performances of Pair 1 were selected for the numerical history match study. Three months averaged steam injection and oil production rates are shown in Figure 4. Many interesting characteristics were identified in the injection and production history.
1. During the first year (April 1997 to April 1998), the operation pressure and oil production rates decreased when steam injection rates were reduced. Operation pressure and oil production rates were positively sensitive to the steam injection rates. This is typically expected for the SAGD process. However, this characteristic was detected mainly during the first year of operation.
2. After the second year of operation, oil production rates responded inversely to steam injection rates. When steam injection rates were increased, oil production rates were reduced and when steam injection rates were decreased, oil production rates were increased.
3. Steam injection was stopped in October of 2002 for about five months while operation pressure and oil production rates were gradually reduced during this period. Similar characteristics were also noticed in 2003 and 2004.
