A Dynamics Study On Surface-driving Progressing Cavity Pump Of Oil Production System

Oil production system with a surface-driving progressing cavity pumptransmits pressure to the down hole pump by sucker rods. The sucker rodstherefore bear tension, torsion and bending moment in a complicated way.Especially when high-duty pumps are used or deep wells are involved, thehardness of sucker rods becomes the major effect of the safety condition ofan oil extraction system. Amechanic study on driving rods in a pump systemand the analysis of their dynamic characteristics for improving their workingprinciple is both theoretically and practically meaningful. The paper builds acalculating concept of the tension, torsion and bending moment that suckerrods bear; and builds the dynamic model and calculating model of theirlongitudinal vibration, wrench vibration and the horizontal vibration in whichthe iMPact of centralizer is accounted, and by which the resonance frequencyof the longitudinal, wrench and horizontal vibration of sucker rods and thecritical rotary speed when the resonance happens can be calculated. Thepaper studies the dynamic characteristics of sucker rods; analyses the causesand solutions of the eccentric wear of sucker rods based on their force state;studies the decentralized rotarywhich causes instabilityand the calculation ofthe correct position for centralizers; and theoretically analyses thedeformation of tubing under pressure as well as quantitatively calculates thedeforming dimension. The paper adopts two experimental testing techniques.One is polished rod pressure testing technique, and the other is electricalparameter. In the paper, a test-data analysis software is programmed,verifying the force state of sucker rods and the analytic vibration theoriesstudied in this paper through nearlya hundred on-site tests and analysis.