Abstract
To solve the issues and difficulties in the high-coupling modelling of beam pumping units and high-slip motors, external characteristic experiments of high-slip motors were performed where the external database and characteristic correlation equations of the motors were obtained through data regression analysis. Based on the analysis of the kinematics, dynamics and driving characteristics of the beam pumping unit, a fully coupled mathematical model of a motor, pumping unit, sucker rod and oil pump was established. The differential pumping equation system of the pumping unit used a cyclic iteration method to solve the problem of high coupling among the motor, pumping unit, sucker rod and the pumping pump. The model was verified by experimental data of field l pumping wells. Theoretical calculations and experimental tests showed that the soft characteristic of the high-slip motor can reduce the peak suspension load of the sucker rod, peak net torque of the gearbox and peak power of the motor. In addition, the results show that the soft characteristic can also decrease the high-frequency fluctuation of the motor power curve and the torque curve of the gearbox. The high-slip motor can improve the smoothness and safety of the pumping well system.
Highlights
The high-slip motor drives the beam pumping unit with several advantages
The high-slip motor has soft mechanical characteristics which adapt to the cyclic alternating load of the beam pumping unit, making the pumping unit system run smoothly and increasing the service life of the equipment [2]
In 1991, Yao [8] et al established an equivalent mechanical model and a differential equation of motion for the dynamic coupling of a high-slip motor and a pumping unit and launched a wave equation for the downhole sucker rod system, but they did not consider the effect of tubing and liquid column vibration on the suspension load
Summary
The high-slip motor drives the beam pumping unit with several advantages. The starting torque is large, and the peak torque of the pumping unit can be reduced, which is suitable for loading the start of the pumping unit [1]. Dynamic coupling modelling equation of sucker-rod string, liquid column and tube strings, increasing the calculation accuracy of the suspended point load of the pumping unit These studies did not consider the effect of motor speed change on the dynamic performance of the pumping unit system. In 1991, Yao [8] et al established an equivalent mechanical model and a differential equation of motion for the dynamic coupling of a high-slip motor and a pumping unit and launched a wave equation for the downhole sucker rod system, but they did not consider the effect of tubing and liquid column vibration on the suspension load. According to the dynamic coupling model of the beam pumping unit and the high-slip motor established, the calculation programme is compiled using the Visual Basic V6.0 language, and the torque test results are outputted by the pumping unit gearbox to verify the accuracy of the theoretical calculation. The influence of the high-slip motor on the dynamic performance of the pumping well was analysed
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