Oil fell to the lowest level in more than 5 1/2 years after Goldman Sachs Group Inc. and Societe Generale SA reduced their price forecasts and Venezuela called on OPEC producers to work together to spur a rebound.

West Texas Intermediate decreased as much as 4.7 percent, and Brent 5 percent, after dropping a seventh week. Crude has to “stay lower for longer” if investment in shale is to be curtailed to re-balance the global market, according to Goldman analysts. Prices need to return to $100 a barrel for economic equilibrium, Venezuelan President Nicolas Maduro said in Iran during a tour of Middle Eastern OPEC members.

“The price forecast cuts by both Goldman and Societe Generale reinforce the fears that have driven us down to these levels,” Gene McGillian, a senior analyst at Tradition Energy in Stamford, Connecticut, said by phone. “We’re hunting for a bottom, but it’s anyone’s guess where that will be.”

Oil slumped almost 50 percent last year, the most since the 2008 financial crisis, amid a supply glut estimated by Qatar at 2 million barrels a day. The Organization of Petroleum Exporting Countries is battling a U.S. shale boom by resisting production cuts, signaling it’s prepared to let prices fall to a level that slows American output that’s surged to the highest level in more than three decades.

WTI for February delivery declined $2.08, or 4.3 percent, to $46.28 a barrel at 10:13 a.m. on the New York Mercantile Exchange. It touched $46.11, the lowest level since April 21, 2009. Total volume was 44 percent above the 100-day average for the time of day.

Brent for February settlement dropped $2.29, or 4.6 percent, to $47.82 a barrel on the London-based ICE Futures Europe exchange. The contract reached $47.61, the least since April 1, 2009. Volume for all futures traded was 52 percent higher than the 100-day average. The European benchmark crude traded at a $1.54 premium to WTI, the least since Oct. 16.

WTI will trade at $41 a barrel and Brent at $42 in three months, Goldman said in a report distributed today, citing excess U.S. storage capacity and predicting inventories will increase over the first half of this year. It also cut its price estimates for six and 12 months.

“To keep all capital sidelined and curtail investment in shale until the market has re-balanced, we believe prices need to stay lower for longer,” said Goldman analysts including Jeffrey Currie in New York. “The search for a new equilibrium in oil markets continues.”

Societe Generale reduced its average WTI price for this year to $51 a barrel from $65 in a Jan. 9 report from Michael Wittner, the bank’s New York-based head of oil research. Brent will average $55 a barrel in 2015, down from a previous estimate of $70.