Michael E. O'Hanlon of the Brookings Institution estimated that if Afghanistan generates about $10 billion per year from its mineral deposits, its gross national product would double and provide long-term funding for Afghan security forces and other critical needs. The United States Geological Survey (USGS) estimated in 2006 that northern Afghanistan has an average  of crude oil,  of natural gas, and  of natural gas liquids. In 2011, Afghanistan signed an oil exploration contract with China National Petroleum Corporation (CNPC) for the development of three oil fields along the Amu Darya river in the north.