San Antonio pipeline operator Howard Energy Partners is entering the Oklahoma market with plans to build a natural gas gathering system in the Sooner State's prolific STACK shale play. Howard announced on Tuesday that the company has entered into a deal with a major North American oil and gas producer to build, own and operate a new natural gas gathering system located in an area of the STACK play that needs more pipeline capacity. Gathering pipelines move natural gas from individual wells to high-capacity and large transmission pipelines.