Luckily refineries that can use canadian heavy oil (like CVE/COP refineries) are making tons of money right now. That helps balance off soem of the bad impact from low heavy oil pricing. That was the idea in the first plac.
COP spun their refineries (and other pieces) off to shareholders as the new Phillips66 company. That happeend last summer so I should not have said COP. CVE owns 50% of two refineries (Wood River in Illinois and Borger in Texas). Both have high end capacity to refine heavy oil - Wood River got a huge new coker that is paid for, in place, and running. I think that the refineries may contribute 500 million in cash flow for Q4.
So their is some balance in that big heavy oil differentials create cheaper feedstock for their own refineries.