Pioneer Natural Resources Company is a top-tier United States independent exploration and production company. With total proved reserves equivalent to more than 6 trillion cubic feet of gas or 1 billion barrels of oil, Pioneer operates in the U.S., Argentina, Canada and Africa. Combined, these assets create a portfolio of resources and opportunities that are well balanced among oil, natural gas liquids and gas, providing both dependable production and an array of quality exploration and development opportunities. The company maintains production from its onshore bases, primarily the Hugoton and West Panhandle gas fields, the Spraberry oil and gas field and the Raton coal bed methane gas field, by reinvesting only a portion of its cash flow and controlling costs. Scott D. Sheffield has been the chief executive officer of Pioneer Natural Resources for more than nine years. He has been with the petroleum and natural gas company for over 27 years. Sheffield earned a SB degree from the University of Texas-Austin. Pioneer Natural Resources Company is headquartered in Irving, Texas.