Last checked at 
* July WCS last at $14.80/bbl under WTI
* July synthetic last at $4.25/bbl above WTI
CALGARY, Alberta, June 6 (Reuters) - Canadian cash crudeprices strengthened on Thursday as reports that refinerymaintenance neared completion spurred expectations for anincrease in demand.
Western Canada Select heavy blend for July delivery lasttraded at $14.80 per barrel below the West Texas Intermediatebenchmark, according to Shorcan Energy Brokers.
That compares with a settlement price of $16.00 below thebenchmark on Wednesday.
Light synthetic crude from the oil sands for July lasttraded at a premium of $4.25 per barrel to WTI, up from asettlement price on Wednesday of $2.00 per barrel above thebenchmark. Trading sources said the sharp rise was difficult toexplain.
Heavy oil prices have been rising in recent days on reportsthat two major refineries that process Canadian crude couldreturn to service this month after prolonged shutdowns.
Oil market intelligence service Genscape said Exxon MobilCorp's 238,600 barrel per day refinery in Joliet,Illinois, was conducting preliminary restartactivities.
The facility, which processes Canadian crude, shut down formaintenance on April 14 and is likely to return to servicebefore the end of this month, according to Genscape.
Meanwhile, BP Plc said an upgraded crude distillationunit at its 405,000 bpd Whiting, Indiana, refinery is onschedule to start up by the end of June.
Prices showed little reaction to news that Phillips 66 is conducting planned maintenance at its 362,000 bpdjoint-venture refinery in Wood River, Illinois.
The company did not give details regarding specific unitsinvolved or the duration of the work, but market sources saidthe maintenance work had already been factored into prices.
