The first Russian oil tanker attempting to deliver crude while under U.S. sanctions made a secret cargo transfer onto another ship, a sign of the lengths to which Moscow is going to undermine the effectiveness of American restrictions on its fleet.

The SCF Primorye was sanctioned by the U.S. Treasury’s Office of Foreign Assets Control in October, after which it didn’t load oil again for about six months. But in late April, the tanker went to Russia’s Black Sea port of Novorossiysk and collected a cargo of Urals crude before embarking on a 7,500-mile voyage to a location about 70 miles east of Singapore.

Russia has shipped about 3.4 million barrels a day of crude so far this year, valued at about $37 billion at the point of export, and working around western sanctions has been part of that. Oil proceeds to the state budget increased almost 50% in May from a year ago, as its crude prices rose and the nation adapted to the measures. Nevertheless, the contorted logistics that the SCF Primorye is involved in show that there are impediments to the trade.

Not long after it arrived east of Singapore, the 900-foot tanker vanished from the automatic identification system, or AIS, where commercial vessels broadcast their locations and destinations for safety reasons. AIS can be turned off by a ship’s crew.

However, after it disappeared, satellite imagery shows that the ship switched its cargo onto another vessel, the Ocean Hermana, on June 3. The secretive transfer would in theory help whoever is buying the oil to distance themselves from dealing with a sanctioned ship and any risk of further actions from the Treasury. Identifying the receiving ship makes it hard to hide the origin of the cargo. 

SCF Primorye, which was holding about 1 million barrels of oil, is owned by Russian state oil tanker company Sovcomflot PJSC. The company declined to comment. 

The two vessels were identified by Bloomberg based on their dimensions, deck configuration and coloring. The identities of both were confirmed by TankerTrackers.com Inc., which specializes in interpreting satellite imagery to spot sanctions-busting tankers. 

The Ocean Hermana is about 20 years old and with an unknown insurer. It has spent most of its recent history shuttling between locations around Singapore and the Malacca Strait and ports in China. 

Equasis, a database set up to promote safe shipping, indicates that its operator is a company called Sygnius Ship Management Pvt in Kolkata. The company said by email that this was incorrect and that its only role was as the vessel’s crewing agent. 

Sygnius forwarded a message on behalf of an operator that it didn’t identify in response to questions from Bloomberg saying that the tanker complied with all relevant rules and regulations, and hadn’t engaged in any unlawful ship-to-ship operation.

Whether the cargo is eventually delivered to a refinery — most likely in China given the location of the transfer — will offer clues as to how easily Russia might be able to repeat the process with its other sanctioned vessels. Since October, almost all of 40 tankers sanctioned by OFAC have failed to load cargoes and only one has been removed from a list of designated vessels. Not all are owned by Sovcomflot.

Bloomberg tracked the SCF Primorye’s movements on AIS and then, when it disappeared from that system, examined modified Copernicus Sentinel data, processed with EO Browser from Sentinel Hub. 

SCF Primorye has now resumed its journey, heading northeast through the South China Sea and showing a draft that indicates it is now empty. The last signal from the Ocean Hermana was on June 10, nearby where the cargo transfer happened. It’s draft indicates that the ship’s cargo tanks are now full.

Another sanctioned vessel, the Bratsk, is already following the route of the SCF Primorye. It’s now in the Indian Ocean, carrying a cargo of Urals crude it loaded at Novorossiysk on May 23, and due to arrive off Singapore on June 17.

More sanctioned tankers owned by Russia’s Sovcomflot PJSC may follow. Another seven disappeared from tracking after entering the Black Sea. They are likely still there, as regulations require them to send automated position signals while transiting the Turkish Straits, making it difficult for them to have sailed into the Mediterranean undetected.