Design Considerations When Rod Pumping Gas Wells

By Bill Elmer, EOG Resources, Inc. and Allan Gray, Lufkin Automation

Many SPE papers have been written over the years on how to pump the deep and difficult wells. However, when it comes to rod pumping gas wells, there is negligible literature. In the past three decades, our industry has transitioned from manually calculating rod pump designs using the method found in API bulletin RP 11L1 to fully computerized dynamic simulations. Most operators with limited engineering resources depend upon third parties to run these computer programs, with the direct result being a loss of a "feel" for the process. By optimizing every component for the lower fluid volumes required for gas well de-watering, installation costs can be minimized. More importantly, mistakes can be avoided that will assure a successful installation, and lowered future operating expenses. This paper will look at every component of the rod pumping system, including rod pump sizes, rod string size and grade; pros and cons of tubing anchors; and pumping unit and driver sizing.Wave equation calculations will be used to support the conclusions made, and the end result will be the presentation of several "Rules of Thumb." A comparison between two actual field installations will be made using dynamometer analysis, with one of the two utilizing these design concepts.