Rio Vista Energy Partners LP, Houston, (Nasdaq: RVEP) plans to acquire substantially all of the assets of privately held, Oklahoma City-based Northport Production Co. for $18 million and will assumed $2 million in debt for a total deal valued at $20 million. Northport has assets in the Midcontinent where is drills, operates and manages wells in Oklahoma, Texas, Kansas New Mexico, Alabama and West Virginia. The company owns and operates more 100 wells and has non-operating joint venture interests in an additional 150 producing properties. The company had unaudited revenue for the year ended Dec. 31 of approximately $4.6 million.