Winter is coming-and so is $100 oil

The prospect of a harsh northern hemisphere winter, an Organization of the Petroleum Exporting Countries (OPEC) supply cut and a volatile geopolitical picture may send oil prices back towards $100 a barrel, a CNBC survey of strategists and traders showed.

Benchmark Brent crude oil (CME:Index and Options Market: .SGICBRB) - used to price two-thirds of oil globally - has entered a bear market, falling more than 20 percent since June, as ample supply and weak demand growth weigh.

CNBC's forward-looking findings show opinion is evenly split over the path oil prices will take in the final three months of the year-although a strong bearish bias persists. Almost half the respondents (49 percent, or 17 out of 35) expect Brent to gain this quarter, while 51 percent (18 out of 35) forecast declines.

"We look for a seasonal pick-up in oil product demand, a cold winter and OPEC production cuts as requirements to prevent a more dramatic slump in the crude oil price," Deutsche Bank (Grey Market: DBFBF) commodity strategists led by Michael Lewis said in a quarterly report on September 30.

The European Union is mediating talks aimed at settling a gas dispute between embattled Ukraine and Russia, and is concerned about disruptions to its own supplies. Europe receives about a third of its gas from Russia, some 40 percent of which is pumped via Ukraine.

'Winter of the Russian Bear'

Some central European countries continue to report declines in Russian gas deliveries, the Wall Street Journal reported on September 22, as tensions between Ukraine and Russia persist in the run-up to winter.

"I think this will be the winter of the 'Russian Bear,'" said Thomas McMahon, CEO of Singapore-based UD Trading Group and the former CEO of the Singapore Mercantile Exchange.

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Russian President Vladimir Putin may be able to make up for lost gas volumes flowing into Europe, McMahon said, because energy deals with Beijing mean "he's got China in his side pocket for revenue."

Meanwhile, OPEC producers may opt to cut supply when they meet on November 27, or may even authorize a decision earlier, if prices continue their relentless slide.

"OPEC has to be really concerned," said Carl Larry, president of Houston-based consultancy Oil Outlooks.

The average price of OPEC's basket of 12 crudes has fallen below $90 a barrel for the first time in two years.

"We believe production cuts by OPEC should allow Brent crude oil prices to stabilize and trade around $100 a barrel, with repeated spikes," said UBS (Swiss Exchange: UBSN-CH) strategists Giovanni Staunovo and Dominic Schnider.

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"Saudi Arabia is well-positioned to act as a 'put' against lower prices. The Kingdom holds much of the world's limited spare capacity of just 2.5-3.0 million barrels a day."

Oil prices in the last three months of this year will be "heavily dependent" on the action taken by swing producer Saudi Arabia, said Fereidun Fesharaki, chairman of energy consultancy FACTS Global Energy and a former energy adviser to the Prime Minister of Iran in the 1970s.

"So far, they have allowed oil prices to fall, and kept production flat at 9.6 million barrels a day,' Fesharaki told CNBC in an email. "We expect they will cut back production and prices will go to around $95."