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Canada crude - Prices strengthen after gas line rupture

CALGARY, Alberta, Oct 17 (Reuters) - Canadian cash crude prices strengthened on Thursday after a rupture on TransCanada Corp's natural gas pipeline in northern Alberta forced oil sands producers to pare output.

TransCanada has not yet said when its damaged North Central Corridor pipeline, which as the capacity to carry as much as 1.6 billion cubic feet of gas per day, will return to service.

But the closure forced some of Canada's largest producers, including Imperial Oil Ltd, Suncor Energy Inc and Syncrude Canada Ltd, to cut back operations as they wait for critical gas supplies to return.

Western Canada Select heavy blend for November delivery was last trading at $29.50 per barrel below the West Texas Intermediate benchmark, according to Shorcan Energy brokers.

The differential had earlier tightened sharply to $26.50 per barrel under WTI, the narrowest level since mid-September, as new of the pipeline outage reached the market.

That compares with a settlement price of $30.00 per barrel below the benchmark on Wednesday.

Traders in Calgary said assumptions that the gas outage would not affect November production helped pare gains.

"When will it be fixed is the question," one crude trader said. "This is quite bad, but it is an October issue."

Light synthetic crude from the oil sands for November delivery strengthened to $9.50 per barrel below WTI, compared with Wednesday's settlement price $10.60 under the benchmark.