bongo has oil / gas, page-16

Basically you have to either borrow stock or sell stock you don't own at current price on the premise that you'll buy the stock on market at some time in the future at a lower cost to you (cover), thus make difference of the sell to buyback gap.

You'd need a broker willing to do it but I'd find it hard to beleive any of the main retail brokers out there would do it. And apart from that, given the recent news it would be rather foolish I think.