The Organisation of the Petroleum Exporting Countries has lowered its long-term estimates for oil demand but says $10tn of investment will still be needed between now and 2040 to cover future needs and prevent a spike in prices. The forecasts, contained in the group’s World Oil Outlook, highlight the delicate balancing act facing Opec and its most powerful member Saudi Arabia as it persists with a strategy that puts long-term exports and market share over short-term financial gain. Lower spending by major companies and oil prices at below $40 a barrel for a prolonged period could have an impact on future oil supplies and lead to a surge in prices. “If the right signals are not forthcoming, there is a possibility that the market could find that there is not enough new capacity and infrastructure in place to meet future rising demand levels, and this would obviously have a knock-on impact on prices,” said Abdalla El-Badri, secretary-general of Opec, in the report.