Oil prices rose on Monday as OPEC reported that the global oil glut has been virtually eliminated, while U.S. crude's discount to global benchmark Brent widened to more than $7, its deepest in nearly five months.
Brent crude ended the day's trading up $1.11, or 1.4 percent, at $78.23 a barrel, its best close since Nov. 25, 2014. The contract hit $78.44 earlier in the session, its highest intraday level since Nov. 26, 2014.
U.S. light crude oil ended Monday's session up 26 cents at $70.96, remaining below last week's intraday 3½-year high of $71.89 a barrel.
The report from the Organization of the Petroleum Exporting Countries "was bullish. That absolute plunge in Venezuelan production ... just highlights how tenuous the market is in terms of the supply and demand balance," said John Kilduff, partner at Again Capital.
The OPEC report, published Monday, showed Venezuelan production at its lowest in decades and said the global oil glut had been virtually eliminated. Even so, OPEC and other producing countries were still trimming output more than their supply-cutting pact required.
U.S. crude's discount to Brent was more than $7, the widest since late December.
"You have the threat that a high enough price will start to activate the 7,700 drilled but uncompleted wells in the lower 48 states," said Walter Zimmerman, chief technical analyst at ICAP TA.
"And meanwhile, if Iranian crude is really taken off the water, its going to impact Brent much more than its going to impact WTI," Zimmerman said.
It is unclear how hard U.S. sanctions will hit Iran's oil industry. A lot will depend on how other major oil consumers respond to Washington's action against Tehran, which will take effect in November.
China, France, Russia, Britain, Germany and Iran all remain in the nuclear accord that placed controls on Iran's nuclear program and led to a relaxation of economic sanctions against Iran and companies doing business there.
"Germany has said it will protect its companies from U.S. sanctions, Iran has said French oil giant Total has yet to pull out of its fields and all the while it seems the Chinese are ready to fill the void created by the U.S."
Some oil analysts have said they expect Iranian crude exports to fall by as little as 200,000 barrels per day (bpd), while others put the figure closer to 1 million bpd.
Michael Wittner, analyst at Societe Generale, forecasts U.S. sanctions will remove 400,000-500,000 bpd of Iranian crude from the global oil market.
"In 2012 the reduction in Iranian crude production and exports was around 1 million bpd," Wittner said. "This time around, we expect much less of an impact."
Also supportive to prices was data from market intelligence firm Genscape showing that inventories at Cushing, Oklahoma, the delivery point for U.S. crude futures, fell more than more than 400,000 barrels in the week to May 11, according to traders who saw the data.
The surge in oil prices comes at a time of tight supply amid record Asian demand and voluntary output restraint by the Organization of the Petroleum Exporting Countries and non-OPEC producers including Russia.
— CNBC's Tom DiChristopher contributed to this report.