Unplanned maintenance at Suncor Energy’s oil sands operation has pushed production to the low end of its forecast range for the year despite the startup of a new production unit, Canada’s largest energy company said.

Suncor said average oil sands output in 2012 is now expected to be closer to 325,000 barrels per day than 340,000 bpd due to unplanned repairs at the company’s base plant in northern Alberta in early November. In October, it had trimmed the upper end of its forecast.

In 2011, its oil sands production averaged 326,500 bpd.

Production in November averaged 318,000 bpd, down 18,000 bpd from the previous month, the company said.

However, the repairs to the oil sands plant are complete and the operation pumped 380,000 bpd at the end of November, it said.

Suncor had said it expected oil sands production to increase 12 per cent and overall oil and gas output 8 per cent in 2013. Capital spending is pegged at C$7.3 billion. Chief executive Steve Williams has signaled that Suncor will not be rushing into major capital projects to boost production at any cost.

The company has pushed back plans to construct the Fort Hills oil sands project, and said it and partner Total will decide by the end of the first quarter whether to go ahead with a multibllion-dollar upgrading plant known as Voyageur.

Williams has already said the proposed facility’s economics are threatened by surging volumes of light shale oil in regions such as the North Dakota Bakken.