Study On Sealing Performance Of Coiled Tubing Ram BOP Rubber Core

As a new type of operation technology,coiled tubing operation technology has the advantages of low cost,simple and time-saving operation,safe and efficient operation,and can solve many problems that are difficult to solve by conventional operation techniques.The coiled tubing ram BOP is the core device to ensure the safe operation of the coiled tubing.When there is a kick/blowout,the BOP needs to be quickly sealed to avoid major safety accidents.The sealing performance of the key seal rubber core determines whether the safety can be finally sealed.Therefore,it is necessary to conduct study on the sealing performance of the coiled tubing BOP ram rubber to ensure the safety of the coiled tubing operation.Firstly,according to the working principle of the coiled tubing BOP,the paper analyzes the structural form,sealing principle and failure mode of the four seals of the coiled tubing BOP.It provides reference for the optimization design and on-site maintenance of the coiled tubing BOP seal structure.Furthermore,according to the reliable and reasonable sealing of the ram rubber core,the mechanical model of the ram rubber core is established to determine the tightness of the rubber core during the sealing process.Secondly,the uniaxial tension and compression experiments were carried out on the rubber core material.According to the relationship between load and deformation and stress and strain,the corresponding stress and strain values were obtained.In the ABAQUS software,different constitutive models were used to fit the experimental data.It is finally determined that the Yeoh constitutive model can most accurately describe the intrinsic properties of the core material.The ABAQUS simulation software is used to numerically simulate the process of sealing the rubber tube of the ram rubber core.It is found that the contact stress of the arc-shaped part of the rubber core is smaller than the contact stress of the flat part,which indicates that the main sealing part of the rubber core has insufficient tightness.According to the above analysis,for the sealing problem of the ram rubber core,combined with the actual sealing part of the rubber core during operation,the design idea of the composite rubber core composed of polymer material and rubber is used to optimize the structure of the ram rubber core.The new rubber core sealing process was simulated and compared with the original rubber core simulation analysis results.It was found that the minimum contact stress of the new rubber core arc part is larger than the original rubber core,so the new rubber core has better sealing performance.The effects of liquid pressure and friction coefficient on the seal of the rubber core were studied.The maximum Mises stress of the rubber core gradually increased from 9.238 MPa to 16.28 Mpa and the maximum Mises stress value remained unchanged.The contact stress gradually increases from 13.18 MPa to 21.31 MPa with the hydraulic pressure,and the contact stress at each point of the PTFE ring gradually approaches the same;The contact stress of the flat part of the rubber core increases with the increase of the friction coefficient,but the degree of increase is small.The contact stress of the lower part of the PTFE ring increases with the increase of the friction coefficient,and the upper contact stress decreases with the increase of the friction coefficient.Therefore,the sealing area of the PTFE ring and the oil pipe is greatly affected by the friction coefficient,and the flat area of the rubber core is less affected by the friction coefficient.Finally,using the test device of the coiled-tube ram BOP rubber core,the improved ram rubber core is installed in the coiled tubing ram BOP,and Perform indoor tests such as the ram BOP sealing performance and the life of the down-drilling.The test results show that the improved seal core sealing performance has reached the test requirements.