A tanker carrying U.S. light sweet crude oil to the United Kingdom paused for 10 days in the Atlantic Ocean, changed destinations and was near Spain on Tuesday, ship tracking data showed.

Seaways Yosemite, which was chartered by Swiss trader Trafigura Group and loaded about 600,000 barrels of WTI Midland crude oil in early-June in Corpus Christi, Texas, was indicating Cartagena as its new destination.

The vessel earlier had been bound for Birkenhead-Tranmere terminal near Liverpool in the UK, according to Refinitiv ship tracking data.

The reason for the delay and detour was not immediately clear.

Data provider IIR Energy tracked an outage last month at Essar Oil UK’s 220,000-barrel-per-day Stanlow refinery near Birkenhead-Tranmere. Stanlow’s crude processing unit has resumed operation following an unplanned mechanical issue, IIR added.

Trafigura declined to comment. Repsol, which owns a refinery in Cartagena, and Essar did not respond to requests for comments.

Another vessel Unity Venture, chartered by BP BP.L and loaded in Houston in early June with 700,000 barrels of WTI Midland oil, also idled in the mid-Atlantic for about 14 days.

It will head to Fredericia, Denmark, according to a person familiar with the matter and ship tracking data.

BP did not immediately respond to a request for comment. Crossbridge Energy Partners, which owns and operates the Crossbridge Energy Refinery in Fredericia, did not reply to requests for comments.

While some ships are chartered with the option to sell the barrels on the water, the vessel racks up demurrage charges for being in use beyond the typical time period, increasing shipping costs.

Source : Hellenic Shipping News