U.S. Blockade and Hormuz Gridlock: Analyzing April’s Oil Market Disruption

A chaotic April ended with the Strait of Hormuz effectively closed for a second consecutive month, cascading oil shortages across Asia and a U.S. blockade choking off Iranian tankers and oil exports.

Iran’s oil exports collapsed 43% over two months, according to data from Vortexa. By May 1, U.S. forces had redirected 44 blockade-busting Iranian vessels across the Arabian Sea and Indian Ocean, adding to economic pressure.

A 12-day ceasefire that began on April 8 was extended but failed to restore commercial transits or freedom of navigation through the Strait, with traffic down 93%. Nearly 900 cargo ships and tankers remain trapped. The month was defined by a series of extraordinary and unprecedented events:

U.S. forces boarded, detained, and are now seeking civil forfeiture of two Iran-trading very large crude carriers, Majestic X (IMO 9198317) and Tifani (IMO 9273337), both interdicted in the Indian Ocean. A third vessel, the Iran-flagged containership Touska (IMO 9328900), was fired on by USS Spruance on April 19 and seized after refusing to comply.

The Iranian Revolutionary Guard Corps seized the Panama-flagged MSC Francesca (IMO 9401116) and Liberia-flagged Epaminondas (IMO 9153862). Both were linked to MSC, the world’s largest container line, which the IRGC said was banned from transits for perceived links to Israel. Both ships are now anchored 9 nm off the Iranian port of Seerik.

U.S. sanctions waivers on Iranian and Russian oil-on-water were extended for a second 30-day period to curb rising global oil prices. OFAC’s General License 134B (April 17) covered approximately 95 million barrels on 244 Russian oil tankers, of which 38% were sanctioned and 29% rated by Windward as high-risk.

Thirty-three ships reversed course from Hormuz transits on April 18 after the IRGC fired on three vessels and reversed an order issued 24 hours earlier by Iran’s foreign minister to “completely open” the Strait.

Fears of Iranian drone attacks or seizures, and the threat of mines laid in the international traffic channel, are undermining shipowner and marine insurer confidence that safe transits can be undertaken. Daily transits are in the range of 7–20 ships, versus the pre-war average of 138.

Iran’s permission-based physical blockade is redirecting ships via a northern route through its territorial waters, amid unconfirmed reports that toll payments are required. Fewer ships are being tracked through a southern corridor via Omani waters.

The Iranian Revolutionary Guard Corps seized the Panama-flagged MSC Francesca (IMO 9401116) and Liberia-flagged Epaminondas (IMO 9153862). Both were linked to MSC, the world’s largest container line, which the IRGC said was banned from transits for perceived links to Israel. Both ships are now anchored 9 nm off the Iranian port of Seerik.

U.S. sanctions waivers on Iranian and Russian oil-on-water were extended for a second 30-day period to curb rising global oil prices. OFAC’s General License 134B (April 17) covered approximately 95 million barrels on 244 Russian oil tankers, of which 38% were sanctioned and 29% rated by Windward as high-risk.

Thirty-three ships reversed course from Hormuz transits on April 18 after the IRGC fired on three vessels and reversed an order issued 24 hours earlier by Iran’s foreign minister to “completely open” the Strait.

Fears of Iranian drone attacks or seizures, and the threat of mines laid in the international traffic channel, are undermining shipowner and marine insurer confidence that safe transits can be undertaken. Daily transits are in the range of 7–20 ships, versus the pre-war average of 138.

Iran’s permission-based physical blockade is redirecting ships via a northern route through its territorial waters, amid unconfirmed reports that toll payments are required. Fewer ships are being tracked through a southern corridor via Omani waters.

U.S. Blockade Imposed on Iran Ports From April 13

The U.S. blockade confined dozens of Iran’s vessels in the Gulf of Oman and Arabian Sea. On April 19, Windward satellite imagery detected seven VLCCs with a combined loading capacity of 14 million barrels.

A further 11 sanctioned tankers in the Arabian Sea and eight in the Gulf of Oman were effectively immobilized within the blockade’s first week, although two, including Vigor (IMO 9262156), were later detected via satellite imagery loading dark off Kharg Island.

Iranian-flagged VLCC Diona (IMO 9569695) switched off its AIS on March 27 after transiting the Strait of Malacca and was redirected by U.S. forces as it sailed toward Iran. It has now been identified at the southern edge of the Chabahar cluster.

Loadings from Iran’s crude export terminal at Kharg Island were measured at 2.2 million bpd in February and 1.25 million bpd in April. The post-blockade pace is around 600,000 bpd.

Adding to pressure, no VLCC or Suezmax laden with Iranian crude has transited the Strait of Malacca since April 24, the longest stretch since the war began. This is the clearest sign yet that Iranian crude is failing to reach Asia.

Vortexa data showed 153 million barrels of Iranian oil in transit, much of it stranded in floating storage west of Hormuz or accumulated in the Riau Archipelago.