Performance Research And Structure Optimization Of Coiled Tubing Slip Ram Blowout Preventer

The slip ram blowout preventer(BOP)can hang the coiled tubing in case of emergency to prevent it from falling into the well.However,due to the interaction of the two,the stress concentration will occur,which will lead to the phenomenon of slips breaking teeth,coiled tubing scratch and collapse,and reduce the service life.Therefore,it is necessary to carry out the finite element analysis of the slip string to study the stress distribution law in the contact area,to carry out the research on the influence of the structural parameters of the slip ram on its working performance,and to give a reasonable structure optimization combination,so as to reduce the damage degree of the slip string and increase the construction success rate.Based on the study of the working mechanism of the slip ram,starting with the structural characteristics of the coiled tubing clamped by the slip,and based on the elastic-plastic mechanics,the theoretical analysis of the elastic-plastic mechanical behavior of the slip string was carried out.According to the stress characteristics of the coiled tubing,the plastic yield criteria and hardening conditions of the slip string under complex stress state were derived.Combined with the theory of plastic increment,the elastic-plastic constitutive relation of the slip string under complex stress state was calculated.The slip ring tooth is the most important part of slip ram.It is in direct contact with coiled tubing in the working process.Based on the contact nonlinear theory and the actual working condition,the finite element calculation model of slip string was established,and the nonlinear contact simulation analysis was carried out.The simulation results of slip ring tooth and coiled tubing were analyzed,and the stress distribution law of the contact area between slip ring tooth and CT and the damage of CT were clarified.The slip hangs the coiled tubing by friction.Therefore,this paper studied the influence of different friction coefficient on the clamping characteristics of the slip string,and gave a reasonable safety range of friction resistance.On this basis,the influence analysis of structural parameters on the working performance of slip ram was carried out in order to optimize the structure of slip ram.The influence of tooth front angle,tooth back angle and chamfer on the maximum stress of slip ram and coiled tubing is studied,and a more ideal combination of structural parameters was selected for finite element analysis.Carrying on the bearing test platform of slip ram,taking the purpose of hanging coiled tubing and the depth of coiled tubing undercut not more than 0.3mm as the acceptance criteria,carrying out the experimental research on the clamp of slip ram on coiled tubing,using the method of finite element simulation and test to evaluate the working performance of optimized slip ram.The test results were compared with the optimized simulation results.The results showed that the slip ram was undamaged and the undercut depth of CT reacheed the acceptance standard.The undercut depth of CT in the test was in good agreement with the undercut depth of the simulation results,which proveed the reliability of structural optimization and the accuracy of the test.