Linn Energy LLC said Monday that chief operating officer Mark E. Ellis had become the new president and CEO.
The company announced in June that Ellis would succeed Michael C. Linn, with Linn staying as executive chairman to focus on long-term strategy.
Ellis, who was also named to the board, joined the company in December 2006 and became president and chief operating officer a year later. He had spent more than 20 years at Burlington Resources and ConocoPhillips.
Linn Energy is an independent oil and natural gas company with about 1.7 trillion cubic feet of proved reserves in the U.S. at the end of 2008.
Linn shares rose 57 cents, or 2 percent, to $28.45 in regular trading. They fell 4 cents in extended trading after the announcement.