(Undated) -- The winter storm that's plunging hundreds of U.S. cities into a deep freeze is shutting down much of the oil patch. Three oil refineries in Port Arthur, including the nation's biggest, have had to stop processing the more than one million barrels a day they usually turn out. The story's the same for refineries in Beaumont, Corpus Christi, and Baytown, as well as Baton Rouge, Louisiana. Texas' energy regulator said Monday that producers in the Permian Basin and the Panhandle have been crippled by "unprecedented freezing conditions."