The U.S. Keeps Blocking Iran’s Ports. Tehran’s Shadow Tankers Have Now Run Out of Oil.

Iran has exhausted the offshore crude stockpiles that helped sustain its oil sales during months of American naval pressure, removing a financial cushion as Tehran confronts the growing economic costs of war.

The Wall Street Journal reported that Iranian oil stored aboard tankers in Asian waters had been depleted by mid-October, citing analysts at commodities-data company Kpler. Those cargoes allowed Tehran to continue supplying Chinese refineries even while the U.S. blockade prevented replacement shipments from reaching overseas customers.

The development follows months of evidence that Iran's export system was becoming increasingly constrained. Reuters reported in September that no Iranian crude cargoes had successfully crossed the Strait of Hormuz toward China since Washington reinstated its blockade on July 14.

Iran continued loading some crude inside the Gulf, but its ability to deliver those barrels to foreign buyers had effectively stalled. China-bound sales consequently depended on oil already positioned beyond the American interception zone, a supply that could be drawn down but could not be replenished.

That offshore inventory had provided a temporary bridge between restricted exports and continued income. The Journal said the accessible floating stockpile had declined from approximately 90 million barrels in mid-July to about 29 million barrels.

The report identified a delay between physical deliveries and their financial consequences. Payments for previously delivered cargoes could continue after the last stored barrels were sold, with receipts potentially drying up around mid-December. That means the exhaustion of offshore supplies does not necessarily translate into an immediate halt to every outstanding oil payment.

The shadow fleet developed to overcome precisely these kinds of commercial restrictions. U.S. Treasury documents describe a system of shipping companies, intermediaries and vessels that moves Iranian petroleum toward Asian customers while obscuring its origin.

A Financial Crimes Enforcement Network advisory identified tactics including falsified shipping documents, manipulated vessel-tracking signals, irregular voyages and transfers of oil between ships. Those arrangements complicate efforts to identify the cargo's source and the parties benefiting from its sale.

Washington has continued targeting the supporting businesses. On October 21, Treasury announced measures against shipping agents and other facilitators it accused of assisting Iranian shadow-fleet operations. The action extended pressure beyond tankers themselves to companies providing services that help the trade function.

There are limits to what the depletion establishes. By October 16, Iran had managed to move some liquefied petroleum gas and jet fuel despite the blockade, including through transfers off Oman. Those shipments involve different products from the crude stockpiles described in the Journal's latest report, but show that some petroleum trade has continued.

The squeeze on Iranian exports also comes as other Middle Eastern producers restore shipments. The Reuters report put regional oil exports at an average of 17.3 million barrels daily in October, above the 16.9 million recorded before the war.