The IEA is concerned about the lack of investment in exploration and production

The International Energy Agency has noted an acceleration in the natural decline of hydrocarbon deposits. This acceleration is linked to the growing proportion of unconventional fields, which are being depleted faster than conventional fields. Non-conventional oil and gas production now accounts for 23% of world production, compared with 3% in 2000.
In the absence of investment, the IEA estimates that world oil production will fall by 5.5 million barrels a year. The agency has calculated that 540 billion dollars a year will have to be invested to keep oil production stable, and that the current level of investment (570 billion dollars) leaves little room to satisfy growing demand.