The U.S. Geological Survey estimated there are at least 665 billion barrels of undiscovered oil in reserves outside United States.
"The USGS estimates that the mean undiscovered, conventional reserve additions in the world total 665 billion barrels of oil, 1,429 trillion cubic feet of natural gas and 16 billion barrels of natural gas liquids," it said.
Its assessment didn't include oil and natural gas fields in the United States, unconventional accumulations or so-called tar sands.
British energy company BP, in its annual review of world energy, said trends in renewable energy development indicate consumption of energy from non-fossil fuels increased substantially. Renewables represent 2 percent of the global energy mix, however, showing most of the world relies on fossil fuels for the bulk of its energy needs.
BP Chief Executive Officer Bob Dudley said at the London presentation of the annual report that emerging economies were putting strains on oil supplies as demand increases.
Nevertheless, he said, fears of peak oil were overblown.