The global oil glut is likely to take longer than expected to clear and may depress oil prices for many more months if not years despite steep investment cuts and project cancellations around the world, executives from oil majors said on Tuesday.

The views from the top ranks of Exxon Mobil, BP and Total were given at the Abu Dhabi International Petroleum Exhibition and Conference (Adipec) in Abu Dhabi as key officials from the Organization of the Petroleum Exporting Countries (Opec) said they expect better prices in 2016.

The discord in views comes as most global majors are slashing their budgets and investments with the aim to be able to generate cashflows with prices as low as $60 per barrel.

And while major producing nations are also reducing spending, they are often facing much tougher choices to keep governments popular.

"I'm not sure we will exit from low prices before many months," Total's chief executive Patrick Pouyanne told the conference.

Oil prices more than halved in the past 18 months because of a global oil glut which arose on the back of a US shale oil boom and a decision by Opec not to cut output to fight for market share with higher cost producers.

BP's and Exxon Mobil's heads of exploration and production Lamar Mckey and Jack Williams both said low oil prices would stay for a while and BP's head of the Middle East Michael Townshend said the group saw oil fluctuating around $60 per barrel for the next three years.

The views are more pessimistic than those of Opec with secretary general Abdullah Al-Badri saying on Tuesday he saw a positive momentum for oil markets building in 2016.

The glut is persisting even though oil majors alone have cut their capital investments by a combined $22 billion this year while scrapping some 80 projects, double the number abandoned in 2014, according to Mckay.

Townshend said he saw Iraq - a major source of additional supply over the past two years - unlikely to be adding to the glut next year. "It is difficult to see a massive ramp up in production next year because of the way the contracts are structured," he said referring to ongoing talks with the government of Iraq about lower investment plans for next year to reduce paybacks to oil majors and thus leave more money for the Iraqi budget.

But as the oil industry becomes more efficient it is quickly learning how to recover more resources from existing fields. "The new reality is that giant fields will produce for much longer," said Mckay.

Williams said his example of rising efficiencies was the cost of well drilling in North Dakota - one of the key US states behind the shale boom - being down 36 percent in the past four years while generating higher production. - Reuters