Prejudgment of Eccentric Wear of Screw Pump Rod Based on Electrical Parameters

Prejudgment of eccentric wear of screw pump rod was conducted by an analysis model that was established according to electrical parameters.Following behaviors were observed in analysis with the model:both torque and axial force changes of the sucker rod could reflect the variation of working conditions;the rod torque was positively correlated with submergence degree and negatively with tubing radius;and when torque and axial force changed,the eccentric wear of rod changed accordingly,which could be reflected by such parameters as current and active power.Data analysis of field fault wells indicated that active power was more highly sensitive than current to the change of working conditions,especially for the small or medium-sized drive unit or motors with light loads;when the sucker rod worn off,current might drop to a certain extent,but the active power changed abruptly;the curve of eccentric wear due to higher wax content,rotation speed and submergence depth was consistent with the results analyzed with the model based on electrical parameters.It was proposed that utomatic speed-adjusting function be used to control the fluctuation of submergence depth;liquid level be changed by automatically adjusting the rotary speed of pump,so as to mitigate the eccentric wear of rod significantly;and reasonable hot washing period of wells was determined by monitoring screw pump automatically and continuously to prevent eccentric wear due to higher wax content.