XTO Energy knows the X's and O's of a successful oil and gas strategy. The oil and gas exploration and production company buys and develops mostly long-lived producing properties to produce oil and gas (including extracting natural gas and from US shale and other tight formations); it also develops unproved reserves. The company's assets are mainly in Arkansas, Kansas, Louisiana, New Mexico, Oklahoma, Texas, and the Rockies; it also has assets in Appalachia and Canada. A subsidiary of Exxon Mobil since 2010, XTO Energy owns interests in about 40,000 producing oil and natural gas wells across the US.