Fault Diagnosis Models Of The Adjustable Diameter And Changeable Toque Pumping Unit Well Based On The Power-Displacement Diagram

Aiming at the problem of low automatization of fault diagnosis of the adjustable diameter and changeable toque pumping unit well,it is urgent to improve the accuracy of the fault diagnosis.Considering the actual angular velocity,the unbalanced weight of structure and the efficiency of motor and gearbox,the relationship between the polished rod load and the input power of motor are derived by analyzing the internal relation between the polished rod load,the output shaft torque of the gearbox,the output shaft power of motor and the input power of motor.Then,the conversion model of the power-displacement diagram based on the dynamometer card is derived.By transforming the dynamometer card in typical working condition into the corresponding power-displacement diagram,11 power-displacement diagrams in typical working conditions are established.The eigenvalue of typical powerdisplacement diagrams are extracted by difference curve method,geometric method,gray theory and curve moment method respectively.Through expert system and grey relation,four working condition diagnosis models based on power-displacement diagram are established.According to the diagnosis results of four diagnosis models and dynamometer card,a multimethod joint diagnosis model of working condition was established.The test of 10 wells in the oilfield shows the average relative error of average normalized power of up and down stroke between the measured power-displacement diagram and the calculated power-displacement diagram are 5.17% and 6.51%,and the average fitting coefficient is 0.91.This shows that this model has a good accuracy,and it also proves the reliability of the typical power-displacement diagram.According to the test of 90 wells in the oilfield,the diagnostic coincidence rate of dynamometer card method is 93.3%,difference curve expert system method is 90.0%,geometric expert system method is 88.9%,gray matrix gray correlation method is 81.1%,curve moment gray correlation method is 85.6%.Through the multi-method joint diagnosis model,the coincidence rate of the diagnosis results is 94.4%,it improves the coincidence rate of diagnosis results in different working conditions.This shows that the model has high accuracy and practicability,and can provide technical support for intelligent diagnosis and production optimization decision in production system of adjustable diameter and changeable toque pumping unit well.