Natural gas will overtake oil as the most used fuel in the U.S. by 2030 on abundant supply, the International Energy Agency said.

So called unconventional supplies, extracted from sources including shale rock and coal beds, will account for almost half of the increase in global output of the fuel by 2035, the Paris-based adviser said in its World Energy Outlook.

Diversifying sources of supply, can “accelerate movement towards more diversified trade flows, putting pressure on conventional gas suppliers and on traditional oil-linked pricing mechanisms for gas,” the IEA said.

Global gas consumption may rise 19 percent by 2017 from 2010 levels as demand surges in Asia and the U.S. while Europe’s usage drops 1.6 percent, the agency said in June. China’s gas consumption will more than quadruple from last year’s level by 2035, boosted by regulatory reforms and policy support, the IEA said. Demand will also rise in India and the Middle East while growth in Japan is limited by higher prices and a focus on renewable sources and energy efficiency.

A boom in producing natural gas trapped in shale has already helped the U.S. surpass Russia as the world’s biggest producer of the fuel and damped prices to a 10-year low in April on the New York Mercantile Exchange.

“The unconventional gas business is still in its formative years, with uncertainty in many countries about the extent and quality of the resource base,” the IEA said. Most of the increase in production will come from China, the U.S. and Australia, it said.