Oil prices will remain below the psychologically important $100-a-barrel mark until at least 2025, according to a draft report by the Organization of the Petroleum Exporting Countries (OPEC), seen by The Wall Street Journal.

In its most optimistic scenario, OPEC, which represents 12 oil-producing countries, forecast that oil will sell for around $76 per barrel in 10 years' time, according to the report.

However, it warned that crude oil could cost as little as $40 per barrel in 2025.

"$100 is not in any of the scenarios," said a delegate at an OPEC presentation last week in Vienna, according to The Wall Street Journal.