(Add details on plant outages)
CALGARY, Alberta, Nov 20 (Reuters) - Two oil sands upgraders in Alberta have warned customers about cuts to synthetic crude output in November because of upsets at the plants, market sources said on Monday.
Shell Canada, a unit of Royal Dutch Shell, has told customers synthetic crude volumes from its 255,000-barrel-per-day Scotford, Alberta, upgrader may be reduced in November and potentially December, trading sources said on Monday.
Shell told customers it took units at Scotford offline on Wednesday because of a valve leak and the duration of the repair was unknown, according to sources.
A company spokeswoman declined to comment.
In a separate incident, the Syncrude oil sands project, which has capacity to produce nearly 350,000 bpd, in northern Alberta has also told customers it will cut synthetic crude volumes by around 5 percent in November, two trading sources said.
A Syncrude spokesman declined to comment.
Trading volumes in the Canadian crude market are currently extremely thin because market players have already nominated how much crude they want to ship on export pipelines next month.
There were no trades in synthetic crude for November or December delivery, according to Shorcan Energy brokers.
On Friday, light synthetic crude from the oil sands for November delivery settled at $5.25 per barrel over the West Texas Intermediate benchmark, while December barrels settled at $2.70 per barrel over WTI. (Reporting by Nia Williams and Catherine Ngai in New York Editing by Jonathan Oatis)