Oil glut weighs on drilling, petroleum stocks

Index dropped 1.3% to 813, reversing its upward trajectory earlier in the day. U.S. refining giant Valero fell 10 cents to $16.93. Sector leader Exxon Mobil dipped 1.8% to $66.21. The Amex Natural Gas Index subtracted 0.3% to 314. Component Devon Energy...