Explanation: Texas has known petroleum deposits of about 5 billion barrels (790,000,000 m3), which makes up about one-fourth of the known U.S. reserves. The state's refineries can process 4.6 million barrels (730,000 m3) of oil a day. The Port Arthur Refinery in Southeast Texas is the largest refinery in the U.S. Texas also leads in natural gas production, producing one-fourth of the nation's supply. Several petroleum companies are based in Texas such as Occidental Petroleum, ConocoPhillips, ExxonMobil, Halliburton, Marathon Oil, Tesoro, Valero Energy, and Western Refining.
