Market confidence failed after news of another big rise in USA crude inventories that have built steadily as U.S. oil production rose this year.
USA crude prices fell through the $50 a barrel support level, with market participants unwinding some of the massive number of bullish wagers they had amassed after the deal.
Oil market saw another sell-off on Thursday (9 March), with the West Texas Intermediate (WTI) falling below $50 for the first time in 2017, on higher-than-expected USA inventories and Saudi energy minister Khalid Al-Falih's comments that an extension of Opec's production cuts can not be guaranteed beyond the summer.
But several analysts remained bullish on oil for the long term.
Oil prices steadied on Friday after dropping to their lowest in more than three months, pressured by heavy oversupply despite Opec-led production cuts. On Wednesday, the benchmark slumped 5 percent, its biggest daily percentage move in a year.
Brent crude was up 35 cents at $52.54 a barrel.
Brent and U.S. crude hit respective session lows of $51.50 and $48.59, levels not seen since the OPEC cuts were announced at the end November.
Unlike the OPEC and non-OPEC state-run producers that have agreed to curb output, there is no mechanism for US independent producers and global oil majors to restrain output.
"I still think we will stick in a fairly narrow range with the current levels reflecting the average price for the remainder of the year and a bottom of around $40 and a top end of somewhere around $60", said Chris Gaffney, president of EverBank World Markets in St. Louis, Missouri.
Wittner said global crude and product demand is also entering a period of seasonal weakness.
The US contract fell below on Thursday for the first since mid-December, when OPEC producers and a group of other countries including Russian Federation agreed on a cut in output to end two years of declining prices.
The resulting rise in oil prices has sparked a rush of new output by shale producers, who this week outlined ambitious production growth plans across the United States.
"The discussion will now center around whether or not Saudi Arabia is willing to give back market share to US producers. or are they ready for yet another round of the market share war", Dominick Chirichella, senior partner at the Energy Management Institute in NY, told Reuters on Thursday.