HOUSTON --ConocoPhillips is rewarding investors with a 20 percent dividend increase and a plan to buy back $10 billion of shares. The Houston oil producer says it will pay 66 cents per share on March 1 to shareholders of record on Feb. 22. The share repurchase plan, if completed, would more than double the amount spent on buybacks last year. Repurchasing shares takes them off the open market and pushes prices of remaining shares higher. Conoco recently has been aggressive in rewarding shareholders while transforming its business. It sold off a number of oil-producing assets during the past few years while focusing on developing North American fields. In 2010, Conoco's earnings increased nearly threefold to $11.4 billion. Shares rose 2.4 percent to $71.75.