The facility planned to reduce December production by a total of 1.6 million barrels due to the operational problems, three market sources told Reuters last week.
Syncrude has restored about half of that 1.6 million-barrel cut, one of the sources said.
A Suncor spokeswoman declined to comment.
Representatives for Syncrude and Imperial could not be immediately reached for comment.
The increase in production pushed the discount for light synthetic crude from the oil sands compared to West Texas Intermediate (WTI) wider, to about $3.50 a barrel on Thursday, traders said.
Light synthetic crude settled at $2.85 below WTI on Wednesday, according to NE2 Canada Inc.
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