(Bloomberg) -- Some of the world’s biggest oil-hauling supertankers are instead loading up vast volumes of diesel in the latest sign of how attacks by Yemen’s Houthis are upending global shipping. 

At least one so-called very large crude carrier, or VLCC, capable of hauling two million barrels of oil is already sailing from the Middle East to Europe, while another is in the process of loading, according to Kpler and ship-tracking data compiled by Bloomberg. 

At least five more are expected to switch to carrying so-called clean petroleum product, a category that includes diesel, shipbroker Braemar Plc said. That would mean about 14 million barrels of the fuel could end up on the huge ships.

The switchover has been at least partly a knock-on effect of Houthi attacks on shipping in the Red Sea and Gulf of Aden that have upended some longstanding trade routes.

The incidents boosted earnings for smaller vessels that haul fuels like gasoline and diesel — known in industry jargon as clean tankers — as the ships sail thousands of miles extra around Africa. At the same time, benchmark crude tanker rates have been easing, giving shipowners an incentive to switch their vessels out of that trade.

While it’s unclear precisely how much diesel-type fuel will end up on VLCCs and what its final destination will be, at least some appears to be heading to Europe from the Middle East.

“Larger clean tankers have faced increased volatility and notably higher rates this year,” in part as ships sail further around Africa, according to Svetlana Lobaciova, principal analyst at EA Gibson Shipbrokers. “In contrast, Suezmaxes and more recently VLCCs have relatively underperformed, with relatively lower spot earnings on benchmark trades at times being substantial enough to encourage larger crude tankers to clean up and compete in the clean tanker market.”

Houthis Impact

The shift in sailing distances as a result of Houthi attacks can be seen in a measure of shipping demand called ton-miles, which multiplies cargo by how far it is transported. This gives a sense of how heavily used the global shipping fleet is. 

A year ago, for refined fuels being shipped from the Middle East, that measure was forecast to increase by 13% in 2024, according to Clarkson Research Services Ltd., a unit of the world’s biggest shipbroker. It is now estimated that it will rise by 17% this year.

Likewise, imports of fuels to northwest Europe were previously expected to rise 16% this year, and those to the Mediterranean by 7%. Those estimates now stand at 22% and 23% respectively, underscoring the increased strain on the global fleet and explaining why traders are turning to bigger ships.

Large volumes of fuel arriving in one go create a sudden influx of supply, a potentially volatile influence on benchmark diesel prices. The norm is for a broadly smoother flow of smaller ships discharging.

Part of the forward curve for ICE Gasoil futures — Europe’s diesel benchmark — traded in a structure signaling oversupply for the first time in almost three weeks on Wednesday.

In addition to the supertankers, crude carriers that haul one million barrels known as Suezmaxes have also been switching over. About 12 of them are likely to transition to carrying clean petroleum products in the near future, Braemar said. Gibson previously said that at least 10 of the vessels had already switched to transporting clean fuels this year.

“As CPP volumes are shipped further around the Cape of Good Hope, transport costs per barrel can be cut by leveraging economies of scale, employing fewer, larger vessels,” Braemar analysts wrote in a report, referring to clean petroleum products.

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