Constellation Energy Partners LLC, Baltimore, (NYSE: CEP) has closed its acquisition of Amvest Osage Inc., a subsidiary of privately held, Charlottesville, Va.-based Amvest Corp., for $240 million. Amvest Osage owns producing and undeveloped properties in the Cherokee Basin in Oklahoma, including a 560,000-net-acre concession for coalbed-methane and shale rights from the Osage Native American Nation. The assets feature 370 producing wells with a general 100% working interest. Amvest Osage is now a subsidiary of Constellation.