The contracts, which allow holders to sell 1000 barrels of oil for $50 each by December, are trading at about $280 on the Nymex, up from $10 at the beginning of the month.
Goldman Sachs and Merrill Lynch analysts say crude may drop another 44% if the world economy slips into recession.
"Opec is going to try to prevent some of the price decline," Francisco Blanch, head of global commodities research at Merrill in London, told Bloomberg television. "It's going to be very difficult to stem a price fall."