* Gas line rupture cuts supply to oil sands projects
* Suncor, Syncrude, Canadian Natural, Imperial cutproduction
* Late in day, TransCanada says gas supplies resuming
* Canadian oil prices strengthen
* Other oil sands operators say no impact from rupture
By Scott Haggett and Nia Williams
CALGARY, Alberta, Oct 17 (Reuters) - TransCanada Corp resumed gas deliveries to most industrial customerslate on Thursday after an earlier pipeline rupture in northernAlberta left some Canadian oil producers scrambling to scaleback production.
The rupture reduced natural gas supplies for most of the dayafter a 1.6 billion cubic foot per day North Central Corridorpipeline ruptured in a remote area about 140 kilometers (90miles) west of Fort McMurray, Alberta.
The outage, which affected producers of more than half ofthe oil sands region's output, cut supplies of fuel used toproduce bitumen and for the upgraders that convert it intorefinery-ready synthetic crude. That forced at least four majoroil sands companies to slow or halt output at facilities thatcan produce more than 800,000 barrels per day of oil. Canadacash crude prices spiked on the news.
"The cause of the line break is not yet known and will bedetermined during a subsequent investigation," TransCanada saidin an email.
It was not immediately clear how quickly output could beresumed. TransCanada said deliveries to most industrialcustomers in the area had restarted and it was working withremaining customers to restore full service.
Most companies did not say how much output had been shut in.
"Operating staff have brought our process units into what wecall 'safe park mode,'" said Pius Rolheiser, spokesman atImperial Oil, which moved to suspend operations at itsrecently opened Kearl oil sands mine. Last month, the companysaid the project was producing 80,000 barrels per day.
"It is too early to say how long operations might beaffected."
Suncor Energy Inc said it was slowing operations atits oil sands projects north of Fort McMurray, where productionaveraged 365,000 barrels per day last month.
The 350,000 bpd Syncrude Canada Ltd oil sands project alsosuspended shipments while Canadian Natural Resources Ltd slowed production at its 115,000 bpd Horizon oil sandsproject and at its Woodenhouse heavy oil operations.
For a FACTBOX on the operations see:
Canadian cash crude prices strengthened after TransCanadaissued its warning early on Thursday, with Western Canada Selectheavy blend differentials for November delivery rising as muchas $2.50 per barrel. The benchmark last traded at $29.50 perbarrel below West Texas Intermediate, slightly higher than onWednesday, according to Shorcan Energy brokers.
Light synthetic crude from the oil sands for Novemberdelivery strengthened by about $1 to $9.50 per barrel below WTI,compared with Wednesday's settlement price of $10.60 per barrelbelow the benchmark.
The line break did not affect all operators in the region.Royal Dutch Shell Plc said its Albian oil sands minewas operating normally. Cenovus Energy Inc said itsFoster Creek and Christina Lake oil sands projects wereoperating as usual.
The North Central Corridor line, built in 2010, is part ofTransCanada's Nova regional natural gas pipeline system.
