Structural Optimization Design Of On And Off Attachment And Supporting Pipe Column In Oil Wellbore

The traditional on and off attachment is mainly used for the plunger pumping well withthe motion form of reciprocating motion, bearing tensile load under the normal working state.With the maturity of the ground drive screw pump oil recovery technology, screw pump hasgradually become the important oil recovery equipment in oilfield, and many new forms ofinjection-production technology gradually applied to the screw pump well, resulting demandfor the on and off attachment which could mainly bear the greater torque load. This paperfocuses on structure optimization design of a new form on and off attachment and supportingpipe column which can mainly bear the torque load used in the downhole double screw pumpoil-water separation system.In this paper, firstly, by using the numerical simulation method, the major problems ofthe on and off attachment with original design scheme are acquired based on structuralanalysis, as the opening structure is used in the upper joint，there is no reliable structure tolimit the radial deformation of the key way under the great torque, and also have a greateffect on the lateral spring claw. In addition, the structure of some parts is not reasonable, thesafety coefficient is a little lower.Then based on the structural analysis conclusion, the two stage design is used for themajor parts of on and off attachment with original scheme respectively, and the structuraloptimization design based on the finite element method is used for structural optimizationdesign of every part respectively. So that the safety coefficient of the new on and offattachment compared to the original design is improved, and the distribution of structurestress and deformation is more uniform.Finally, in this paper, the stress analysis is excecuted for the thread joint part of thesupporting pipe column called hollow sucker rod, according to the results of finite elementanalysis of threaded joints, the shape optimization is used to improve the stress distribution ofthe thread joint, at the same time the bearing capacity is also increased.The work of this paper provided certain theoretical basis and reference for furtherresearch to the on and off attachment which could bear larger torque load on it.