The discount on benchmark heavy Canadian crude versus West Texas Intermediate inched wider on Thursday:
Western Canada Select heavy blend crude for October delivery settled at $21.25 a barrel under WTI, according to NE2 Canada Inc, widening 25 cents from the previous day.
WCS has been under pressure for much of the summer as a result of the release of predominantly sour crude from the U.S. Strategic Petroleum Reserve (SPR).
Oil sands supply is expected to pick up in coming months as companies ramp up production into year-end, market players said.
Global oil futures fell over 3% to a one-week low on a tentative agreement that would avert a U.S. rail strike, expectations for weaker global demand and continued U.S. dollar strength ahead of a potentially large interest rate increase.