Canada crude-Spreads tighten as refinery restarts near

* WCS quoted at $23/bbl under WTI

* Synthetic sells for $2.75/bbl under WTI

* Citgo says no production impact from unit shutdown

CALGARY, Alberta, July 9 (Reuters) - Canadian crude discounts shrank on Monday as Canadian and U.S. refineries that run heavy and light supplies neared restart after a busy maintenance round.

Western Canada Select heavy blend for August last sold for $23 a barrel under benchmark West Texas Intermediate, compared with $26.75 a barrel under WTI late last week. The differential has tightened by nearly $7 a barrel since the start of the month.

Light synthetic, upgraded from bitumen wrung from the Alberta oil sands, was quoted at $2.75 a barrel under WTI, compared with $3.90 a barrel under late last week.

Market sources said there was no major operational issue driving up the Canadian barrels, only a steady drawdown in storage volumes and steady demand. The widening of WCS spreads early this month had surprised many.

Beginning late this week, some refineries are slated to restart operations after weeks of planned maintenance. Imperial Oil Ltd has said its 186,000 bpd Strathcona refinery near Edmonton, Alberta, is due to restart around the middle of July.

Units at Marathon Petroleum Corp's 206,000 bpd refinery in Robinson, Illinois, are also scheduled to return to service during the period.

Another Imperial plant, the 121,000 Sarnia, Ontario, facility, is expected to restart units by mid- to late July.

On Monday, Citgo said there was no production impact from a compressor shutdown at its 167,000 barrel a day Lemont, Illinois, refinery on Sunday.