US shale energy creates global oil 'supply shock' An IEA forecast in November predicted that the US would become the world's biggest oil producer by 2017 thanks to shale energy. But the process behind the boom has proved controversial, with environmentalists worried that the unconventional technology involved, known as fracking, poses a major threat to the environment and may trigger earthquakes. On the back of shale output, the IEA said it expected North American supply to grow by 3.9 million barrels per day (mbd) from 2012 to 2018, or nearly two-thirds of total forecast non-OPEC supply growth of 6.0 mbd. But North America was "just one part of the story" the IEA said, as production capacity in traditional OPEC suppliers in the Middle East will continue to grow in the next five years, "though adversely affected by growing insecurity in North and Sub-Saharan Africa" in the wake of the Arab Spring uprisings. OPEC capacity, which counts for 35pc of today's global oil output, is expected to gain 1.75 mbd to 36.75 mbd in 2018, about 750,000 barrels per day less than under a 2012 forecast. The IEA, an OECD offshoot that tracks the energy market for the world's industrialised nations, meanwhile raised marginally its earlier outlook for global oil demand growth in 2013 to 90.6 mbd. The forecast for non-OPEC supply in 2013 meanwhile was raised 50,000 to 54.5 mbd due to strong output in North America. Ms van der Hoeven also spoke of a "two-speed" recovery in demand for oil, in which non-OECD nations in Asia and Africa are becoming the driving force in place of western markets.