Freezing temperatures across Texas during the extended holiday weekend forced energy companies to shut oil refineries in the largest U.S. crude-producing state and restricted natural gas pipeline operations. The rare deep freeze prompted the state’s electric grid operator to impose rotating blackouts, leaving nearly 3 million customers without power. President Joe Biden declared an emergency on Monday, unlocking federal assistance to Texas. Texas produces roughly 4.6 million barrels of oil a day and is home to some of the nation’s largest refineries, spread throughout the Gulf Coast. In Midland, heart of the U.S. Permian shale region, temperatures were in the single digits Fahrenheit. Motiva Enterprises said it was shutting down its Port Arthur, Texas, complex, which includes its 607,000 barrel-per-day refinery—the largest in the United States. Exxon also began shutting its 369,024 bpd Beaumont refinery and its 560,500 bpd Baytown refinery and adjoining chemical plant in Texas, sources familiar with …