Here's How Iran’s ‘Shadow Fleet’ Is Outsmarting the U.S. Blockade
Despite a U.S. naval blockade in the Gulf of Oman, Iranian oil worth over $2 billion has been quietly transferred ship-to-ship near Indonesia's Riau Islands, bound for China.
The United States Navy has deployed a blockade across the Gulf of Oman, determined to choke off Iranian oil revenues. But thousands of kilometers from the Persian Gulf, in the warm waters near Indonesia's Riau Archipelago, another story is unfolding, one conducted mostly in silence, with transponders switched off and satellite imagery as the only witness.
A Washington Post investigation, drawing on satellite imagery, ship-tracking data, and analysis from firms including TankerTrackers, Windward, and Kpler, documented at least 13 tankers offloading Iranian crude in covert ship-to-ship operations near the Riau islands since April 16. The cargo, approximately 22 million barrels estimated at over $2 billion, is transferred from laden vessels to empty ones, obscuring its origin before the oil continues to China.
"The Riau area has long been used for ship-to-ship transfers of Iranian crude, enabling onward movement to China, Iran's largest buyer." - Windward Maritime Intelligence
The maneuver is not new. Maritime intelligence firm Windward has tracked the Riau Archipelago as a fixture of Iran's sanctions-evasion architecture for years. Tankers arriving laden switch off their AIS transponders mid-transfer, then reappear outbound through the Strait of Malacca, their Iranian cargo now disguised behind a paper trail pointing elsewhere.
How the "shadow transfer" route works
Some tankers have begun taking an even more evasive path: bypassing the Strait of Malacca entirely in favor of the Lombok Strait near Bali, a longer route, but one with less surveillance exposure. TankerTrackers documented an Iranian VLCC supertanker carrying nearly two million barrels that evaded U.S. naval forces and reached the Far East via exactly this path.
There are signs that the blockade is biting at the source. Windward reported that as of early this week, no large laden Iranian tanker had passed through the Strait of Malacca for ten consecutive days, the longest such gap since the conflict began. Kpler's data shows floating storage of Iranian crude near the Riau area has fallen from around 90 million barrels in February to roughly 42 million today, suggesting the pipeline is draining faster than it is being replenished.
U.S. officials have maintained that the blockade is effective, pointing to billions in lost Iranian revenues. The Navy has also expanded operations beyond the Gulf, boarding Iranian-linked vessels in the Indian Ocean and signaling that international waters offer no refuge. Yet the Riau transfers illustrate the durability of a shadow fleet infrastructure built up over years, one that can continue delivering oil already at sea long after new exports are stopped at the source.