Global oil traders have started to charter supertankers to store crude at sea, to await better markets as they did in the 2009 the last period of steeply falling prices.

Big traders - Vitol, Trafigura and Shell - have booked enormous tankers for up to 12 months, shipping sources told Reuters.

The recent 50 per cent fall in oil prices allows traders to profit by storing crude for delivery months later when prices recover.

Vitol, the world's biggest independent oil trader, has chartered the 441,58-dwt TI Oceania, with its three million barrel capacity.

"In 2009 freight rates were extremely low and owners were willing to put their ships out on charter in order to mitigate weak spot rates," said Christian Waldegrave at leading tanker owner Teekay.

"In a rising freight market, such as we are in now, I would think that owners would be more hesitant to fix out their ships on time charter unless they felt strongly that rates were about to decline."