Wouldn't refineries have bought up contracts for quite a number of months in the future at a much lower price than $100?

Just because something is bought cheap don't mean it's worth less.

If refined product is being sold at 85$bbl equivalent, they could make more money selling the crude at £100.
So although the company may be making a profit if they bought the crude futures, or arranged contracts for less than 85$, the actual refining would be losing 15$ of profit.

Maybe the oil companies want to keep profits low to avoid the usual calls for them to be taxed into the ground.

Also, doesn't Saudi Arabia sell at a discount to U.S. refineries?

I also read recently that Iraq was selling to the US at a pretty substantial discount of around $80 per barrel.