Evaluation on energy saving effect of variable speed operation of beam-pumping unit

The variable speed operation technology of the pumping unit is used in a number of domestic oilfields, and evaluation on its efficiency also varies. A mathematic model has been built based on the variable speed coupling running theory of the pumping unit, and its “energy-saving and load-reduction” effectiveness was comprehensively evaluated and analyzed. The result shows that the variable speed operation technique can reduce the motor power and motor torque, reduce the reduction gearbox torque and peak load on suspension point; however, the “over-stroke” phenomenon is not obvious, and the pump load increases. The variable speed operation technique can favorably adapt to the changes of strokes, stroke frequency and submergence, but under poor balance effectiveness, the unfavorable element of “over-stroke” may occur, esp. when the initial phase angle of variable speed operation curve has deviation, then it will heavily affect the overall working performance of the entire pumping system, leading to failure of startup or sudden shutdown.