Several crude grades in North American are already trading inside the single digit territory as the market tries to force some output to shut-in. Canadian Western Select, the benchmark price for the giant oil-sands industry in Canada, fell to $5.06 a barrel on Friday. Southern Green Canyon in the Gulf of Mexico is worth $11.51 a barrel, Oklahoma Sour is changing hands at $5.75, Nebraska Intermediate at $8, while Wyoming Sweet prices at $3 a barrel