Saudi oil tankers are increasingly disabling their Automatic Identification Systems (AIS) to avoid attacks following the Houthi blockade of the Red Sea, causing a state of "dark shipping" at key terminals like Yanbu. This has severely distorted export data, with different agencies estimating Saudi export volumes for the same period with discrepancies of millions of barrels per day.
The International Energy Agency (IEA) and OPEC now face unprecedented uncertainty in their global supply assessments. Although Saudi Arabia has diverted some crude northwards to mitigate risks, its actual export volumes and destinations have vanished into a "data black hole," increasing the risk of oil price volatility.
Where to begin
According to reports, the Houthi group warned international shipping companies on the 20th that vessels trading with Saudi ports could face military strikes, expanding the scope of their previously announced maritime blockade. Since the blockade took effect on July 20, cargo loading at Saudi Arabia's Yanbu port has frequently operated as "dark ships," with one analyst noting that all liftings at the port last week went without AIS activation.
Another analyst observed that about 70% of loadings on Saudi Arabia's west coast in recent weeks have been in "dark ship" mode, and every shipment from Yanbu since July 23 has involved vessels lacking continuous AIS coverage. Concurrently, safety risks in Red Sea shipping persist, with a missile attack on a commercial vessel in the Bab el-Mandeb Strait on the 11th resulting in six deaths and ten injuries.
Vast data discrepancies emerge
The information vacuum caused by the blockade has directly led to significant divergences in export estimates from different agencies. For the week starting August 3, one firm estimated Yanbu's crude exports fell from 2.71 million to 2.38 million barrels per day, while another showed a sharp drop from 4.04 million to 1.78 million barrels per day. A third estimate, however, indicated exports rose from about 420,000 to 850,000 barrels per day.
For the same port and time period, data from different sources can vary by millions of barrels per day. Since vessel AIS data is a fundamental tool for tracking global crude trade and estimating supply-demand balances, its absence makes it difficult for the IEA, OPEC, and market participants to independently verify Saudi Arabia's actual export volumes. For one of the world's largest crude exporters, this "data blind spot" could amplify market misjudgments regarding supply gluts or shortages.
Shifting Saudi export routes northward
In response to Red Sea shipping risks, Saudi Arabia is adjusting its crude export routes, diverting some barrels northward to Mediterranean markets via the Suez Canal or Egypt's SUMED pipeline. Shipping data shows a clear decline in vessel transits through the Bab el-Mandeb Strait, with an average of about 32 ships per day last week, down from roughly 50 before the Houthi blockade.
Satellite imagery further indicates a significant contraction in loading activity at Saudi Red Sea crude terminals. One analyst noted that loading activity has fallen by about half since the blockade took effect, and the average crude tanker storage capacity at the King Fahd and Muajjiz terminals has dropped from approximately 10 million barrels to about 5 million barrels per satellite pass. This suggests Saudi Arabia is reducing shipping safety risks by adjusting transport routes and minimizing its exposure to Red Sea ports, but it also makes it more difficult for the global market to track the actual flow of its crude.
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