Oil and gas explorer Pioneer Natural Resources' frontier is not on the Western prairies, but below ground in the oil and gas basins of West Texas, a gas basin in the Southern Rocky Mountains, and elsewhere. The large independent exploration and production company reported proved reserves of about 664.4 million barrels of oil equivalent in 2015. The vast majority of the company's reserves are found in Texas (primarily in the oil rich and relatively low cost Permian Basin oil fields) and in Colorado (the Raton gas field). Pioneer Natural Resources has stakes in more than 9,794 net producing wells.