S.G. Gibbs, K.B. Nolen, Fred Morrow & Bill Lynch; Nabla Corporation
Pump off controllers have earned a place in the technology of rod pumping. Many methods exist for sensing when a well has pumped off. Most widely used are techniques based on the surface dynamometer card or motor speed or production rate. This paper describes several methods for sensing pump off using the downhole pump dynamometer card. These include areas inside of the pump card, areas outside of the pump card, set point and liquid fillage, among others. Procedures for calibrating the controllers are described together with provisions for high fluid level recovery. Combining the liquid fillage method with variable frequency drives and eddy current drives is presented as a way of performing variable speed - no stop control. Pump card monitors (PCMs) hold promise of being useful devices which are easy to apply and comprehend.