(Bloomberg) — As crude prices continue to get dragged down by a global glut that shows no signs of abating, oil traders may find some profit by going to sea.

The market structure for Brent crude, the benchmark for more than half the world’s oil, now makes it viable to store supplies in a vessel to potentially lock in profits on a sale six months later, according to a Bloomberg survey of four traders as well as a shipbroker and a charterer. About five to 10 tankers have been chartered to most likely hold oil near Singapore, according to Jonathan Lee, chief executive of Tankers International LLC.

Crude is extending declines as OPEC’s members squabble over output limits, threatening the group’s effort to trim an oversupply. But traders can make a profit by storing cargoes at sea even amid tumbling prices, provided there’s a viable contango — a market structure where oil for delivery today is lower than those in future months. The difference has to be big enough to cover the costs of hiring a storage ship to hold the supply until profits can be locked in with a sale later.

Brent crude for delivery in the future has averaged $3.52 a barrel higher than the latest shipments since the beginning of last week, potentially making up for the cost to hire a tanker for half a year.

A six-month time charter on a very large crude carrier, or VLCC, that can carry about 2 million barrels of oil would cost $32,000 to $35,000 a day, according to the shipbroker and charterer in the Bloomberg survey. That’s equivalent to $2.85 to $3.15 a barrel. January Brent futures traded at $47.47 a barrel on Wednesday, lower than the July contact at $50.90 on the London-based ICE Futures Europe exchange.

‘Window of Opportunity’

“The widening of Brent’s market contango has led to the opening of a window of opportunity for floating storage to be viable,” said Den Syahril, a Singapore-based analyst at industry consultant FGE. “The current contango in crude futures is just wide enough to make floating storage workable.”

Most varieties of crude from Africa, North Sea and the Asia Pacific region are priced off the Dated Brent benchmark, meaning traders can potentially benefit from holding on to such grades at sea. Apart from freight, storing crude on tankers would also involve costs including that for ship fuel, insurance and finance.

The State Oil Co. of the Azerbaijan Republic, known as Socar, has booked the VLCC Grace 1 via a six-month time charter to store oil off Singapore, according to three traders and shipbrokers who asked not to be identified because the information is confidential. The vessel is expected to reach Singapore on Nov. 8, ship-tracking data show.

While demand for storage ships is lower compared with early 2015, a series of older vessels have been booked by a handful of traders for four to six months near Singapore from mid-December, said Lee of Tankers International, which transports oil worldwide in a fleet of very large oil tankers owned by independent shipowners.

Industry consultant JBC Energy GmbH had said in July that the drop in freight rates and shrinking availability of traditional storage options prompted “creative approaches to holding on to oil.”

Trading houses including Vitol Group, Koch Supply & Trading LP and Glencore Plc, plus the in-house trading arms of BP and Royal Dutch Shell Plc, collectively made billions of dollars from 2008 to 2009 stockpiling crude at sea. At the peak of the floating storage spree, sheltered anchorages in the North Sea, the Persian Gulf, the Singapore Strait and off South Africa each hosted dozens of supertankers.

Bloomberg News by Serene Cheong, Sharon Cho and Alex Longley