Anadarko Petroleum ( APC) announced strong first-quarter earnings that topped Wall Street estimates by 13 cents a share, buoyed by rising oil and natural gas prices and high sales volume. But net income dropped following an accounting change at the Houston energy company. Anadarko reported net income of $392 million, or $1.55 a share, for the quarter ended March 31. Last year, net income for the same period was $418 million or $1.63 a share, including the accounting change. Wall Street analysts estimated the company would earn $1.42 a share for the quarter on expectations that turnaround efforts of new president and chief executive, James Hackett, would begin to show. In a statement, Hackett said strong sales volumes helped improve Anadarko's balance sheet. Anadarko shares rose to $54.30 in midday trading, up $1.40 from Thursday's close. Quarterly sales volume rose 8% to 49 million barrels of oil equivalent, up from 45.3 million barrels of oil equivalent the previous year. North American natural gas sales were flat at 1.723 million cubic feet a day, up 1 % from 1.705 million cubic feet a day the year before.