Mark Shore....."oil is a globally traded, fungible commodity"
If oil is a "fungible commodity" then why is there such a price difference between Brent and WTI? I believe it's currently a spread of about $5 US?  Brent tends to trade at a higher price even though WTI is better quality. If they were fungible then there should be no price differential (WTI producers would sell at the Brent price increasing supply thereby lowering the Brent price) 
Isn't that basic economics?