Sinopec International Petroleum Exploration & Production Corporation

Sinopec has one million employees and is the world’s fourth-largest company by revenue after Royal Dutch Shell, Walmart and Exxon Mobil; the fifth-largest is China National Petroleum. With their deep pockets, the companies have been investing heavily in North American shale businesses; Sinopec paid $2.2 billion in 2012 for a 30 percent stake in Devon Energy’s shale gas and oil operations in the United States.