* August WCS last at $14.00 per barrel below WTI
* August synthetic last trading at $3 per barrel above WTI
* Traders say volumes very thin after Alberta floods
By Nia Williams
CALGARY, Alberta, June 27 (Reuters) - Canadian oil traders braced for a wild ride next week as the aftermath of two major pipeline closures as well as the cleanup from record floods in southern Alberta are likely to feed volatility when a new trading window opens at the start of July.
News that the 307,000 barrel per day Trans Mountain pipeline had been shut down for the second time in two weeks weighed on demand for heavy crude. Meanwhile the extended closure of a smaller line in northern Alberta was forcing producers to shut in output, supporting synthetic prices.
Trading activity was thin, however, with dealers awaiting the reopening of the monthly trading "window", a roughly three-week period at the start of each month during which traders buy and sell crude and can nominate shipments on pipelines.
Also, some traders were still displaced by the record flooding that hit Calgary this week.
"The market is dead," one Calgary-based crude trader said. "Most people are out of the office."
Another trader said price activity next week could be volatile as a result of the pipeline closures and floods.
Nexen Inc, owned by CNOOC Ltd, and Suncor Energy Inc both said they have reduced production at their oil sands operations as parts of the Enbridge Inc pipeline system that serves the region remained closed after it spilled crude near Fort McMurray on Saturday.
Kinder Morgan Energy Partners LP said its Trans Mountain line - which carries oil sands crude and refined products across the Canadian Rockies to the Port of Vancouver and Puget Sound - was shut on Wednesday after workers found a small amount of contaminated soil near Hope, British Columbia.
Both leaks could intensify environmental opposition to controversial proposals to expand Canada's pipeline network so landlocked oil sands crude can reach global markets.
The alternative method of crude-by-rail also looks set to come in for criticism after five rail cars carrying diluent, which is blended with raw bitumen so it can flow through pipelines, derailed on Thursday on a sinking bridge over the swollen Bow River in Calgary.
Western Canada Select heavy blend for August delivery last traded at $14.00 per barrel below the West Texas Intermediate benchmark, according to Shorcan Energy Brokers.
That compares with a settlement price of $16.00 per barrel below WTI on Wednesday. It was well below nine-month highs around $10 per barrel below the benchmark hit earlier in June.
The impact of the Trans Mountain closure was modest compared with June 12, when prices slumped after an earlier small leak forced the line to shut for two days.
Kinder Morgan said on Thursday it was working to restart the line later in the day subject to consultation with regulators.
Light synthetic crude from the oil sands for August delivery last traded at a premium of $3 per barrel over WTI, unchanged from Wednesday's settlement price.
"We're working with Enbridge to get the pipeline operating as quickly as it is safe to do so," Nexen spokeswoman Patti Lewis said in an email. She declined to provide specific numbers on how much production rates were reduced.
Enbridge, Canada's largest pipeline company, also shut its 345,000 bpd Athabasca pipeline and Waupisoo line, which can carry up to 600,000 bpd, as a precaution. The Waupisoo and part of the Athabasca lines have now reopened, but Enbridge had no estimate for when the system will be completely restarted.
The company said it believed ground movement was responsible for the spill. Northern Alberta was also hit by heavy rains and severe flooding earlier this month.
Thin liquidity in the market was exacerbated by the fact that most Calgary traders continued to work from home after unprecedented flooding forced companies to evacuate their offices in the city's core last Friday.
Power has been restored to most of Calgary's downtown, but city authorities urged employees to work from home as clean-up efforts continue.