Marco Dunand, chief executive of Mercuria Energy Trading, said world oil supplies were tight and this would probably keep prompt prices for North Sea Brent above forward barrels with the market in backwardation for the foreseeable future. 

"We see $100 as a floor for Brent going into next year unless OPEC decides to change their policy and supply extra barrels to the market," Dunand said. 

"We anticipate a situation where the market will remain reasonably tight for a while." 

Oil ministers of the Organization of the Petroleum Exporting Countries meet in Vienna on Dec. 14 to review output. Industry analysts say a cut in output is unlikely to find support among most Gulf Arab OPEC members while oil prices remain strong. 

Brent futures for January traded on Thursday around $109 per barrel, close to their average price so far this year. 

Dunand said a major geopolitical shock, such as a war between Iran and the west which could close the Hormuz Strait in the Middle East Gulf, could push prices up very sharply. 

"With the situation in the Middle East, there are risks to the upside," Dunand said. "The market has already started pricing in some sort of Iranian tension or conflict, but obviously the market would have a long way to go if there was a serious conflict. 

"If there were to be a general conflict and the Strait of Hormuz were to be closed, not something we are expecting, it wouldn't be unrealistic to see the market to go to $130 or $150 per barrel. But I see the chance of that being reasonably low." 

Headquartered in Geneva, Switzerland, Mercuria is one of the top five energy traders with a turnover of around $75 billion, moving almost 120 million tonnes of oil, coal and gas a year. 

Dunand and Mercuria co-founder Daniel Jaeggi, both Swiss, are influential figures in the global energy market with stakes in oilfields in Argentina and Canada, coal mines in Kalimantan in Indonesia and oil trading units in Singapore, Houston and across Europe. 

Dunand said the United States was better-supplied with oil than many other parts of the world and this should keep the futures price curve for US crude, known as West Texas Intermediate or WTI, close to flat for the next few months. 

Recent tightness in WTI nearby futures months, which has kept much of the US crude oil futures curve in backwardation for the last few weeks, was not likely to last, he said. 

"There is no justification for strong backwardation in WTI given the level of oil production in North America and the level of stocks right now," he said.

"We anticipate the WTI structure to be reasonably close to flat for some months." 

But Brent was much stronger. 

"Brent is a different animal. North Sea production has been in decline for a while, (Russian) Urals exports into Europe are also in decline, so the market is moving into a deficit from a surplus. In order to attract the barrels into a low stock environment, you have to have backwardation," he said. 

"I am expecting the Brent backwardation to soften a bit in the second quarter of next year. I expect backwardation for Brent to stay for the foreseeable future, but maybe not as strong as it has been." 

Dunand said Brent should thus stay at a premium to US crude but the spread between the two crude benchmarks was volatile and even quite small changes in the balance between the two markets could move the differential. 

A market is said to be in backwardation when nearby prices are at a premium to later, forward contracts. 

US crude futures traded at a discount of around $9.10 per barrel below Brent at 1100 GMT on Thursday. The spread hit a record high of more than $28 in October. 

"WTI will underperform Brent for a while unless there is a major disruption somewhere. The spread will clearly not stay at the $15 to $20 per barrel (discount for WTI) which we have seen this year," Dunand said. 

He said a Brent premium of $5 to $10 was more likely: "I think the spread will eventually settle around that level."