Oil traders are resorting to storing more and more oil at sea amid swelling output in the Atlantic region, a sign the market is far from the kind of rebalancing that OPEC would have hoped for when the group set out last year to bring down global stockpiles. The amount of oil stored in tankers reached a 2017 high of 111.9 million barrels earlier this month, according to Paris-based tracking company Kpler SAS. Higher volumes of storage in the North Sea, Singapore and Iran account for most of the increase, Bloomberg reported. The build-up occurs even as the Organization of Petroleum Exporting Countries and 11 other nations led by Russia cut supplies. Trading companies including Trafigura Group and Vitol Group have recently chartered older supertankers for as long as eight months, and some of the vessels are likely to be used for floating storage, according to a research note Monday from Pareto Securities AS.