Calculation of dynamic loads of the sucker rod pumping system in CBM wells

The mathematical model of dynamic loads was developed based on an analysis of the polished rod load of beam pumps, and the variation of the dynamic loads and the computation of the minimum and maximum limits during a complete pumping cycle were given out by solving the model. Field examples verify that it is necessary to take into account the inertial and vibration loads while calculating polished rod loads. During the prophase of the pumping production, the dynamic to polished rod load ratio is relatively large. Then the ratio decreases rapidly and becomes small after entering stable production. Moreover, the total deformation of rod and tubing in CBM wells is much smaller than that in oil fields, and the deformation caused by the dynamic loads is also relatively small. The result of this work is the calculation of the dynamic loads. The application of this calculation for the sucker rod pumping system in CBM wells can give the desired accuracy of polished rod load and the dynamometer cards, which provides a reasonable basis for the design and selection of beam pumps.