US Energy Sector has Broad Early Gains; Denbury Shares jump

    Shares of energy companies rose Thursday as gasoline supplies dipped and US retail prices topped $2 a gallon, on average, for the first time in months.     Shares of Exxon Mobil Corp. (XOM) and Chevron Corp. (CVX) added 0.7% and 1.3%, respectively, in early action. Together, they comprise about 14% of...