NEW YORK (Bloomberg) -- Crude ended Friday higher after a curious, late-morning spike left analysts scratching their heads.

The market was little changed during morning hours of trading, but rocketed upwards just before 11:30 a.m. in New York, with no news catalyst identified by traders and analysts. The U.S. benchmark crude ended the session 1.9% higher on Friday, driving futures to post a 0.5% rise this week.

“When the market falls into sideways trading in a band, you get a lot of price fluctuations that you have to turn a blind eye to,” said Gene McGillian, a market research manager at Tradition Energy in Stamford, Connecticut. “This area between $58 and $64, the market inside that, is still consolidating and looking for signals.”

While the Organization of Petroleum Exporting Countries and allied producers trim output to tighten global markets, an ongoing rise in U.S. crude production threatens to block OPEC’s efforts. However, the International Energy Agency said this week that the decline in Venezuela’s oil output could exacerbate a global supply deficit later this year.

West Texas Intermediate for April delivery advanced $1.15 to settle at $62.34/bbl on the New York Mercantile Exchange, the highest level in more than a week. Total volume traded was about 25% below the 100-day average.

Brent for May settlement climbed $1.09 to end the session at $66.21/bbl on the London-based ICE Futures Europe exchange. The global benchmark traded at a $3.80 premium to WTI for the same month.

While record U.S. production beyond 10 million barrels a day has weighed on oil’s rebound, a sense of uncertainty was heightened by a slew of recent events like the firing of Rex Tillerson as U.S. secretary of state, the potential delay of Saudi oil giant Aramco’s initial public offering, talks of a trade war and expectations that Venezuelan production will plunge.

“You’ve got a lot going on, on the world stage,” Tamar Essner, an analyst at Nasdaq Inc. in New York, said by telephone. “The more unexpected elements of this week’s developments were on the macro, international, geopolitical front. We are setting ourselves up for a little volatility ahead.”

Other oil-market news. Hedge funds boosted their net-bullish ICE Brent crude oil bets by 0.1% in the week ended March 13, according to weekly ICE Futures Europe data on futures and options show. Gasoline futures climbed 1.1% to settle at $1.9459/gal on Friday, the highest level since August. The U.S. oil rig count rose by four rigs to 800 this week, according to Baker Hughes data. Saudi Arabia’s willingness to delay the initial public offering of state oil company Aramco to 2019 has several motivations, from regulatory risk to competing projects in the government’s crowded agenda.