So, I think I remember we desire ME oil because it is the sweet kind.
That being said ... how much of all of this oil is sweet, and where is it ... and how much is the 'sour' ?
Many grades of oil, besides sweet/sour (sulfur content) the heavy/intermediate/light (°API, gravity) make a big difference as well.
Landed Costs of Imported Crude by API Gravity
http://tonto.eia.doe.gov/dnav/pet/pet_pri_land3_k_m.htm
We import all grades.
Percentages of Total Imported Crude Oil by API Gravity
http://tonto.eia.doe.gov/dnav/pet/pet_move_ipct_k_m.htm
1% Sulfur is considered "Sour". Much, but not all, of the Middle East Crudes are sour.
World Oil Qualities
http://www.meglobaloil.com/MARPOL.pdf
Sour Oil is that which has high concentrations of Sulfides. Hydrogen Sulfides (H2S) are the most difficult to refine, because the gases that accompany it are very deadly. Only 10 parts per million will cause a person to become unconscious. Above that and instant death will occur. It acts much like a nerve agent.
H2S is also highly soluble in water, so it’s disposal is also costly and difficult. It usually has to be flared off.
The Canadian field is dominated by “sour crude”, which is why many Canadian distillates have such a Sulfurous odor to them. Particularly Gasoline from Canada. It has that “rotten egg” smell to it, which characterizes the smell of H2S. In fact, if you can smell H2S, it is in concentrations that are still safe. Concentrations of it that are deadly are undetectable by smell, because it has already disabled your nervous system and sense of smell. Your only defense then will be sight, because the gas is so heavy, it is visible in that it displaces the air around it.