Investors who placed summer bets that oil prices would fall below $100 a barrel are set to make huge profits on Monday, with some speculators reaping a return of more than 2,000 per cent in less than six months.

The expiry of the December put options – derivatives that give holders the right to sell at a predetermined price and date – means some investors will be selling oil at prices as high as $100-$120 a barrel, well above Friday’s close of $57.04 a barrel.