Oil’s Billion-Barrel Buildup at Sea Points to Sanctions Stress

A buildup of a billion barrels of oil on the world’s oceans includes a disproportionately large amount of crude from nations subject to some kind of sanctions — a sign the measures are bringing a degree of disruption to the oil trade.

Of the surge in oil on tankers since the end of August, as much as roughly 40% of the increase is barrels from Russia, Iran, Venezuela, or unclear origin, according to vessel-tracking data from Vortexa, Kpler and OilX. Even the lowest estimate, at about 20%, is a larger share of global crude production than the three nations have.