Iranian attacks on tankers have gutted the ship-to-ship oil transfer system outside the Strait of Hormuz, cutting supertanker crossings from eight to two per day and threatening the supply chain underpinning nearly 20% of global seaborne crude.
Energy investors and macro traders tracking crude exposure should note that the disruption directly compresses the volume buffer the U.S. military-assisted transfer scheme had provided since May, raising the risk of fresh price volatility in Brent and WTI benchmarks 1.
Key Takeaways
- Supertanker Hormuz crossings collapsed from eight to two daily.
- Ship-to-ship transfers fell from three pairs to just one.
- U.S. says ~14 million barrels/day still flows; data disputed.
Market Reaction & Context
The Strait of Hormuz corridor – through which roughly 20% of global oil supply transits – has been contested since the Iran conflict began in late February 2026. Compared with the late-June peak of eight supertanker crossings per day, the current average of two represents a 75% collapse in direct strait traffic, according to ship broker Clarksons 1.
Each very large crude carrier (VLCC) can carry up to 2 million barrels, meaning the reduction from eight to two daily crossings represents a potential daily throughput loss of up to 12 million barrels via direct transit alone. The parallel ship-to-ship (STS) transfer mechanism – which had been processing tens of millions of barrels since early May – has now nearly stalled, with maritime sources putting recent STS activity at just two or three transfers in recent days, down from a busier cadence visible in satellite imagery as recently as July 11 1.
For macro and sector readers tracking competitive positioning in energy markets, this supply shock dynamic is consistent with the broader shipping disruptions that have already lifted oil prices through the conflict period, and mirrors how earlier sanctions-era pressures reshaped crude flows globally.
Detailed Analysis: How the Workaround Unraveled
Since the conflict’s outbreak, a U.S. military-guided STS operation had served as the primary release valve for Gulf crude exports. Tankers operating on one of two makeshift coastal routes – hugging either the Iranian or Omani shoreline – shuttled cargoes through Hormuz with clearance from Washington or Tehran, offloading to waiting vessels in the Gulf of Oman 1.
The July 18 satellite sweep reviewed by Reuters showed only a single pair of tankers conducting STS operations off Oman’s coast – a sharp contraction from the three pairs visible on July 11 1. Iran’s Revolutionary Guards compounded the pressure on Monday, saying two oil tankers had “exploded” and been immobilised after attempting to transit via what Tehran called an “unsafe” route.
Some shipping companies had already begun avoiding the U.S. military-guided scheme following a wave of Iranian vessel attacks that triggered insurance and safety concerns, according to sources cited by Reuters last week 1. That withdrawal by commercial operators has effectively eroded the scheme’s throughput capacity from both ends.
The situation also echoes patterns seen in other conflict-adjacent energy corridors – a dynamic similar to how Ukrainian drone strikes disrupted Russian energy infrastructure, forcing market participants to re-price supply risk premiums rapidly.
Washington’s Counter-Narrative and the Data Dispute
U.S. Energy Secretary Chris Wright pushed back on the bearish read of public shipping data, telling ABC News on Sunday that official figures were “incorrect.” Wright said the seven-day trailing average showed flow through the waterway running at just under 7 million barrels per day, with an additional near-7 million barrels per day moving via bypass pipelines.
“So, we’re at a little under 14 million barrels a day … That’s two-thirds of pre-conflict traffic, dramatically up from where we were back in March,”
Wright said, adding that Washington would continue to assure traffic through the strait “without Iran’s cooperation” 1. The gap between the secretary’s figures and what satellite imagery and ship-broker data show remains unresolved, a uncertainty that itself carries market implications as traders attempt to model actual supply availability.
Satellite outages and limited public ship-tracking data have further obscured the full picture of Gulf crude exports, making independent verification difficult 1. Investors monitoring crude allocations from Gulf producers – already recalibrated following broader OPEC output shifts – should weigh the Wright figures against the Clarksons vessel-count data cautiously, given the conflicting signals.
Outlook
With the U.S.-assisted STS mechanism effectively reduced to near-zero visible activity, the Gulf’s export resilience now rests heavily on whether Washington can restore tanker confidence in the transit scheme – or whether Iran’s continued interdiction campaign forces a more sustained supply reduction. The halt of Iranian oil sales earlier in the conflict had already begun shifting crude flow dynamics; the latest deterioration in STS activity adds a new layer of tightness that commodity desks will need to factor into near-term positioning.
Any further escalation in Iranian attack tempo, or additional shipping-company withdrawals from the U.S.-guided scheme, could push the effective daily throughput meaningfully below the 14 million barrel figure Washington cited – a scenario that would likely accelerate upward pressure on benchmark crude prices.
Not investment advice. For informational purposes only.
References
1Jonathan Saul (2026-07-20). “Oil transfer activity in Gulf of Oman slows following ship attacks, data shows”. Reuters. Retrieved 2026-07-20.
2(2026-07-20). “Oil transfer activity in Gulf of Oman slows following ship attacks, data shows”. Internazionale / Reuters. Retrieved 2026-07-20.
3Reuters (@reuters) (2026-07-20). “Oil transfer activity in Gulf of Oman slows following ship attacks, data shows”. Threads. Retrieved 2026-07-20.
4(2026-07-20). “Oil transfer activity in Gulf of Oman slows following ship attacks, data shows”. MarketScreener. Retrieved 2026-07-20.