Saudi crude exports from the Red Sea are increasingly vanishing from view as tankers switch off tracking signals to avoid attacks by Yemen's Iran-aligned Houthis, with analysts saying all recent Yanbu loadings have been conducted "dark".
The Houthis declared a maritime embargo against Saudi Arabia on July 20, opening a new front against the United States and its allies in the Iran war.
Since then, they have claimed attacks on Saudi-linked tankers, Yanbu oil facilities and, most recently, the Jazan refinery on the Red Sea coast, prompting more vessels to operate without publicly visible tracking data.
The growing use of so-called dark voyages is clouding visibility into Saudi oil exports, making it harder to assess the degree to which the Houthi threats may be disrupting crude flows.
Ship-tracking firms have produced widely differing export estimates - data which is used by the International Energy Agency, OPEC and traders to assess global oil supply and forecast market trends.
In the week beginning August 3, data analytics firm Vortexa estimated Yanbu loadings fell to 2.38 million barrels per day from 2.71 million the previous week, while Kpler estimated a sharper drop to 1.78 million bpd from 4.04 million, and AXSMarine calculated a rise to 850,000 bpd from about 420,000 bpd.
Saudi Aramco did not respond to a request for comment.
CONDUCTED DARK
Those trying to monitor shipments rely on a vessel re-appearing on tracking systems once it has left the high-risk area, using satellite data to cross-check movements and try to fill in the gaps.
"Last week Yanbu liftings were all conducted dark. We're not seeing any loadings with Automatic Identification System (AIS) on at the moment," Vortexa analyst George Morris said.
Kpler analyst Nhway Khin Soe said about 70% of Saudi west coast loadings over the past few weeks were dark, adding that all Yanbu cargoes loaded since July 23 involved vessels without continuous AIS coverage.
Shipping traffic through the Bab al-Mandeb Strait at the southern tip of the Red Sea had already been affected by two years of sporadic Houthi attacks on commercial shipping. An average of 32 vessels a day transited the waterway last week, according to Kpler data, down from about 50 a day before the group announced its latest blockade.
Ship-tracking data shows that Saudi Arabia has been sending more oil north through the Red Sea, either via the Suez Canal or Egypt's SUMED pipeline, which links Ain Sokhna on the Red Sea to Sidi Kerir on the Mediterranean coast.
Crude and condensate loadings at Sidi Kerir averaged a record 2.17 million bpd last week, around 50% higher than the previous week, with about 90% of the total volumes Saudi crude, Vortexa's Morris said.
Major tanker operator DHT previously exited the Red Sea via Bab al-Mandeb when lifting oil.
"That has become a bit more challenging as of late," DHT CEO Svein Moxnes Harfjeld said on an earnings call last week. "It's fair to say most of the VLCC (supertanker) loadings, not just ours, have been directed north, northwest now."
