When a financial institution goes out and buys an oil storage facility or rents a fleet of oil tankers for the express purpose of holding oil out of the market while 'betting' that the price will increase, they are speculating pure and simple.
It's been estimated that close to 10% of the available oil was being held off the market this way in 2007-2008, certainly enough to drive prices higher and ensure these players won their 'bets'.
It's been estimated that close to 10% of the available oil was being held off the market this way in 2007-2008 10% would be about 8 million barrels a day. Nearly 3 billion barrels a year.
Where did you find that estimate?