Practical Parameter Estimator for Dynamometer Card of Rod Pumping Systems by Measuring Terminal Data of Drive Motor

Diagnosis for rod pumping systems usually requires special instruments used on the surface and the bottom of the well. The need for these external instrumentation increases the cost and complexity of rod pumping system and reduces system reliability. To solve this problem, since significant information about properties of rod pumping system is hidden in instantaneous terminal parameters of the induction motor, this paper establishes a practical parameter estimator that combines the T-type equivalent circuit model of an induction motor and the "four bar linkage" model of beam pumping unit. With this practical model, by measuring the terminal characteristics of the induction motor driving beam pumping unit, the surface dynamometer card is acquired in order to identify oil well properties. The practical application in oil fields proved the effectiveness and practicability of the parameter estimator in this paper.