Exxon Mobil Corp and Chevron Corp, two of the world’s largest oil producers, on Friday posted improved quarterly earnings that benefited from double-digit percentage increases in production from the top U.S. shale field. Shares of both companies rose about 3 percent. The two U.S. oil majors missed the first stage of the shale boom in the Permian Basin of West Texas and New Mexico and have been investing billions of dollars to make up for lost time. They are betting their size and other businesses offer advantages smaller producers cannot duplicate. Combined, the two companies pumped 677,000 barrels of oil and gas per day in the shale field last quarter, close to a fifth of […]