“Markets fluctuate, but we know that science does not. You have to be patient. The cycle from discovery to deployment can take decades.”

Royal Dutch Shell has confirmed it is reviewing the case for selling some of its North Sea assets in the wake of its £35bn takeover of rival oil and gas producer, BG Group.

Neil Atkinson, head of the IEA’s Oil Industry and Markets Division, said in Singapore on Wednesday. About $300 billion is needed to sustain the current level of production, and nations including the U.S., Canada, Brazil, and Mexico are facing difficulty in keeping up investments, he said.

North American oil and natural gas drillers will need to cut an additional 30 percent from their capital budgets to balance their spending with the cash coming in their doors even if crude rises to $40 a barrel, according to an analysis by IHS Inc.A group of 44 North American exploration and production companies are planning to spend $78 billion on capital projects this year, down from $101 billion last year.

Oil companies are cutting investment, slashing jobs and selling off pipelines and other assets as crude prices plunge. “It’s going to be a very turbulent year for our industry,” says BP CEO Bob Dudley.

Three leading US shale oil producers have announced steep cuts in their planned capital spending, as they set their budgets to respond to the collapse in crude prices.

Last month, David Rubenstein, a founder of private-equity firm Carlyle Group, said he anticipates “maybe the greatest energy investing opportunities we’ve ever seen.” Marc Lasry, founder of hedge fund Avenue Capital, has described energy as a “once-in-a-lifetime opportunity.”

While tens of thousands of jobs have already been cut in 2015, more redundancies are expected this year as companies narrow their focus.

Moody’s last month also projected average prices of West Texas Intermediate crude at $40/bbl in 2016, $45/bbl in 2017, and $50/bbl in 2018. The 2016 price is down $8/bbl from the firm’s earlier forecast.

The foreign investment arm of India's top oil explorer ONGC is targeting $10-$12 billion of oil and gas asset purchases over the next three years, including more corporate acquisitions, its managing director said.