Oil prices jumped over 2 percent Monday to their highest since November 2015 after long-time bear Goldman Sachs said the market had ended almost two years of oversupply and flipped to a deficit.
Also pushing prices up were growing output disruptions in Nigeria, where local militants have made repeated attacks on installations operated by Chevron and others.
U.S. crude futures were up 98 cents, or 2.1%, at $47.19 a barrel at 0645 Eastern Time. Brent crude futures, the international benchmark, were trading at $48.83 a barrel, up $1 or 2.0%.
Supply disruptions around the world of as much as 3.75 million barrels a day have wiped out a glut that pulled down oil prices by as much as 70 percent between 2014 and early 2016.
The disruptions triggered a U-turn in the outlook of Goldman Sachs, which had long warned of global storage hitting capacity and of yet another oil price crash to as low as $20 a barrel.
"The oil market has gone from nearing storage saturation to being in deficit much earlier than we expected," Goldman said.
"The market likely shifted into deficit in May ... driven by both sustained strong demand as well as sharply declining production," it said.
However, Goldman cautioned that the market would flip back into a surplus in the first half of 2017 as it said prices around $50 a barrel in the second half of 2016 would see exploration and production activity picking up.
In Nigeria, output has fallen to its lowest in decades following several acts of sabotage.
In the Americas, U.S. officials warned they were growing increasingly concerned by the possibility of an economic and political meltdown in Venezuela amid low oil prices. Venezuela's oil production has already fallen by at least 188,000 bpd this year.
In the U.S., crude production has fallen to 8.8 million bpd, 8.4 percent below 2015 peaks as the sector suffers a wave of bankruptcies.
And in China, output fell 5.6 percent to 4.04 million bpd in April, year-on-year.
Countering this, supply rose from the Organization of the Petroleum Exporting Countries (OPEC) as its producers engage in a race for market share. OPEC pumped 32.44 million bpd in April, up 188,000 b/d from March, the highest since at least 2008.
Also preventing steeper price jumps was a recovery in output in Canada following closures due to a wildfire, as well as bloated global crude storages.
"The inventory buffer may be preventing full price recovery and...the market is rightly nervous about the sustainability of outages," said Morgan Stanley.
Barclays said that "while the supply-side disruptions are supporting oil market balances, refinery margins are starting to weaken, especially in Asia," adding that weaker demand from those refiners could produce "downside risk to prices in Q3 16."