Mechanical Behavior Simulations Study On Sucker Rodstring Of Screw Pump In Vertical Well

Compared with beam pumping unit, The surface-driven screw pump oil extractionsystem has gotten more and more wide application in the oil field for its advantages,which include remarkable energy saving effect, low cost of equipment, and wideadaptability, etc. However, with the increase of deepness of oil well, and With the wideapplication of technology of polymer flooding and combination flooding, The fracture andthread-off of driving rod in screw pump well become more and more frequent, which notonly increases the cost of maintenance, but also affects the oil production. Therefore,researching on the fracture and thread-off mechanism of sucker rod has importanttheoretical significance and practical application value. This paper will mainly carry outthe following aspects:Considering the environmental loading of surface-driven screw pump oil extractionsystem, A solid model of screw pump is established by using Computer Aided Designtechnology. The friction torque of stator-rotor, which includes different configurationparameters of screw pump, is calculated by using Computer Simulation Technology. Aformula is obtained, which is used to calculate the friction torque of stator-rotor, Theformer calculation method is improved.Considering the mechanical characteristics of driving device and gearing, thetorsional vibration of sucker rod string and screw pump. A dynamic simulation model onsurface driven screw pump oil extraction system is established, which is used for thestart-up and stop process. The whole simulation algorithm is established, which hassatisfactory result with a higher degree of accuracy and faster solution speed than theformer independent module algorithm. The simulation result make clear the fracture andthread-off situation of sucker rod.Considering the influence of incident flow resistance and resisting moment whensucker rod eccentrically rotates. The space beam model and two-directions spring modelare established, which are used for the steady running process. Finit element simulationmodel on sucker rod was established,The distributing characteristics of torsion, bending moment, stresses, contact pressure along the depth direction are obtained, The stress andstrength finit element calculation method of sucker rod is proposed."Mechanical simulation software of sucker rod string with surface driving screwpump " is developed by Using Visual Basic6.0. the variation of torsion, revolving speed,stresses of sucker rod at the start-up, steady running and stop process can be simulated byusing this software, which can provide basises for sucker rod design, strength calculation,fracture and thread-off analysis. etc.