US oil settles down $1.29, or 2.81%, at $44.63 a barrel

Shell Oil's drilling rig Polar Pioneer in Port Angeles, Wash., on May 12, 2015.
Jason Redmond | Reuters

Crude oil fell on Friday after Goldman Sachs slashed its price forecast through next year, while global equity markets traded mixed on worries over the economic outlook and whether the Federal Reserve will raise interest rates next week.

U.S. crude futures' front-month contract settled down $1.29 at $44.63 a barrel. The front-month in Brent, the global benchmark for oil, slid 75 cents to settle at $48.14.

Earlier Friday, data showed U.S. energy firms cut oil rigs for a second week in a row, a sign the latest price declines may be causing some drillers to put on hold their recently announced plans to return to the well pad.

Drillers removed 10 rigs in the week ended Sept. 11, bringing the total rig count down to 652, oil services company Baker Hughes said in its closely followed report. At this time last year, drillers were operating 1,592 oil rigs.

Energy companies removed 13 rigs in the week ended Sept. 4, after adding rigs in six of the past eight weeks.

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What are the causes of the summer oil price weakness?
What are the causes of the summer oil price weakness?

Joining Germany's Commerzbank and a long list of other banks in cutting price projections, Goldman lowered its 2016 forecast for U.S. crude to $45 a barrel from $57 previously, and Brent to $49.50 down $62.

"The oil market is even more oversupplied than we had expected and we forecast this surplus to persist in 2016," Goldman said in a note entitled "Lower for even longer."

Citing "operational stress" as a growing downside risk to its forecast, Goldman said crude could fall further to near $20 a barrel. "While not our base case, the potential for oil prices to fall to such levels ... is becoming greater as storage continues to fill."

Crude prices have more than halved over the past year, with Brent tumbling from nearly $120 a barrel in the middle of 2014 to almost $42 last month. The price collapse came after oversupply filled oil storage tanks around the world, pushing commercial and government inventories to all-time highs.

Analysts say the market is rebalancing, but high stocks will continue to weigh on prices into next year.

Read MoreNon-OPEC supply set for big fall: IEA

Germany's Commerzbank also lowered its price forecasts on Friday, saying Brent was likely to trade at $55 by the end of this year before rising to $65 by end-2016.

"It will take time to get rid of the oversupply," Commerzbank senior oil analyst Carsten Fritsch told Reuters Global Oil Forum.

Investors largely ignored a relatively bullish report from the Paris-based International Energy Agency, which advises the world's biggest economies on energy policy.

The IEA said a move by the world's big oil exporters in OPEC, led by Saudi Arabia, to defend their market share by not reducing production appeared to be working.

Saudi Arabia: No need for oil summit
Saudi Arabia: No need for oil summit

"Oil's price collapse is closing down high-cost production from Eagle Ford in Texas to Russia and the North Sea," the IEA said in its monthly report.

The agency, which advises the world's biggest economies on energy policy, said reductions in non-OPEC oil production "may result in the loss next year of half a million barrels a day—the biggest decline in 24 years."

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But traders remained bearish.

"The oil market is looking for something a little more concrete than the forecasts," said Harry Tchilinguirian, global head of commodity strategy at BNP Paribas.