NEW YORK (MarketWatch) — Oil futures plunged Monday, with the U.S. benchmark trading below the $46-a-barrel threshold for the first time in nearly six years after Goldman Sachs cut its crude outlook, predicting prices will remain low for a lengthy period.

West Texas Intermediate crude oil for February delivery CLG25, fell $2.29, or 4.7%, to close at $46.07 a barrel after trading as low as $45.90. The close was the lowest since April 2009. The move followed a 0.9% loss during Friday’s regular session on the New York Mercantile Exchange. WTI futures are down more than 57% from a June 2014 high of $107.26 a barrel.

Meanwhile, Brent North Sea crude oil for February UK:LCOG5, the global benchmark, lost $2.68, or 5.4%, to $47.43 a barrel, its lowest finish since March 2009.

Monday’s drop follows some sharp cuts by Goldman Sachs to its oil-price projections. The bank’s energy analysts revised down their three-month forecast for WTI crude to $41 a barrel from a previous estimate of $70. They see WTI at $39 a barrel in six months and $65 a barrel in a year, versus previous price forecasts of $75 and $80, respectively.

They see Brent at $42 in three months, $43 in six months and $70 in 12 months versus previous estimates of $80, $86 and $90, respectively.

While Goldman appears to be playing catch-up, it’s the firm’s expectations for prices to remain depressed well into 2016 that cleared the way for renewed selling pressure, analysts said.

“A price target for Brent crude of $50.40 for the end of this year would suggest that Goldman doesn’t foresee many production cuts this year, which when you consider that prices are already below cost for so many producers as well as the debt levels of many US shale companies, is quite surprising,” said Craig Erlam, strategist at Alpari UK in London.

SocGen also cuts, Saudi billionaire says $100 oil never again: In addition to Goldman Sachs, Société Générale also cut its oil price forecast for Brent crude by $15 to average $55 a barrel in 2015. For Nymex WTI crude, the investment bank dropped its price target by $14 to $51 a barrel, citing a buildup in oil storage and inventories in the first half of this year.

Brent had similarly experienced deeper losses than Nymex crude on Friday, and Citi Futures analyst Timothy Evans said this was because “demand is seen as weaker in the international market, and much of the supply adjustment to lower prices is expected to take place in the U.S.”

Markets won’t be seeing $100-a-barrel oil again, said Saudi billionaire businessman Prince al-Waleed bin Talal in an interview published in USA Today late Sunday.

See: Oil above $100? Never again, says Saudi Prince Alwaleed.

Elsewhere in the energy complex, February gasoline US:RBG5 gave up 4.87 cents, or 3.7%, to close at $1.2745 a gallon, while February heating oil US:HOG5 dropped 4.89 cents, or 2.9%, to $1.6541 a gallon.

February natural gas US:NGG15 plunged more than 15 cents, or 5.1%, to $2.7950 per million British thermal units, its lowest close since September 2012.