Costar Midstream LLC and Energy Spectrum Partners VI (ESP VI) have partnered to acquire gas processing assets in the Granite Wash area of the Texas and Oklahoma Panhandle. Costar said it plans to build a “sizable” midstream business focusing on gathering and processing assets that can be acquired and developed. This is the first portfolio investment for ESP VI, which is a $998.7 million private equity fund focused on midstream infrastructure. Energy Spectrum has more than $2.3 billion of capital under management. ESP VI, the firm’s most recent fund, closed recently with commitments of $998.7 million. Recently privately held Crestwood Midstream Partners LP completed an acquisition of midstream assets in the Granite Wash (see Shale Daily, April 5).