An Iranian crude oil supertanker anchored off Singapore. Picture: REUTERS
An Iranian crude oil supertanker anchored off Singapore. Picture: REUTERS

London — Iran’s oil tankers are starting to disappear from global satellite tracking systems with just less than six weeks to go until US sanctions are due to hit the country’s exports, making it harder to keep track of the nation’s sales.

No signals have been received by shore stations or satellites from 10 of the Persian Gulf nation’s crude-oil supertankers for at least a week, according to tanker tracking data compiled by Bloomberg. The most likely explanation is that the vessels’ transponders have been switched off, making it more difficult to track the their movements.

When they were last seen, the 10 vessels were holding about
13-million barrels of crude and condensate, a light form of crude extracted from gas fields. If they’re now full, that would rise to about 20-million barrels.

An 11th supertanker, the Deep Sea, last signaled on September 17 as the ship was heading toward the Persian Gulf from Khor Fakkan in the United Arab Emirates, showing its destination as Iran’s Kharg Island oil export terminal. It re-appeared early on September 25, exiting the Persian Gulf, with its signal indicating it had taken on a full cargo destined for Vadinar in India.

The National Iranian Tanker Company didn’t immediately respond to a request for comment.

The disappearance of Iran’s tankers will make it increasingly difficult to monitor ship movements as the November 4 deadline looms for buyers to halt purchases of Iranian crude and condensate or face being blocked from the US financial system. The three full vessels last seen heading out of the Persian Gulf were all showing destinations in China.

The loss of the signals could be the result of seasonal atmospheric conditions, which can cause problems in winter in parts of the world where their capture relies on satellites, rather than shore stations. But such disruptions are usually short lived and signals should have been received from ships once they left the Persian Gulf, unless their transponders have been switched off.