Research On Variable Speed Operation And Optimization Technique Of Beam Pumping Unit

The load rate of motor is low when beam pumping unit works in normal condition,and polished rod load always changes periodically and irregularly,which affects the balance of the pumping system.In some situations the reducer gears may also occur impacts on the back.All these features will increase the energy consumption of pumping unit.At present,some oil field in the domestic is working on variable speed operation technique to achieve the goal of energy saving.By means of field experiments,three wells data was obtained under the constant speed driving and variable speed operation in this paper,which is about the motor power,motor torque,crank torque and dynamometer card.The coefficient of variation and correlation analysis was used to study the application effect and mechanism of variable speed drive technique.And on the basis of model simulation,the crank angular velocity optimization model was established to get optimal scheme of variable speed drive on beam pumping system.The results of data analysis of three wells show that the variable speed drive technology reduces the peak of the motor power,motor torque,gearbox torque,and polished rod load by 36%,28%,34%,and 0.23% respectively.And the change law of motor rotational speed,motor rotor angular acceleration and polished rod velocity can directly affect and application effect of variable speed drive technique.According to the comparison between the measured data and the simulation data,the calculation accuracy of the system simulation model established in this paper can reach 70%~80% in constant speed driving or variable speed driving.According to single factor optimization analysis of the motor speed,motor rotor angular acceleration,and polished rod velocity,there are three methods in reducing the peak of the motor power,motor torque and polished rod load having a good effect.One is decreasing of the motor speed in overloaded area,and increasing the motor speed in light load area.The second is using the inertia torque to balance the load torque.The third is achieving the trapezoid shape curve of polished rod velocity.And by using the crank angular velocity optimization model,the average reduction of the peak of the motor power,motor torque and polished rod load can reach 10% to 20%.