Analysis On The Sealing Characteristic And Criterion Of Premium Connection With Dynamic Load

When the premium connection is in service downhole,due to the fluid flow in the switch well and the tubing,it will be subjected to a time-varying load,that is dynamic load.Under the action of the dynamic load,the premium connection will fail to seal.There are relatively few studies on sealing criteria.Therefore,this paper analysis on the sealing characteristic and criterion of premium connection with dynamic load.In this paper,by analyzing the characteristics of the premium connection structure and the typical seal failure form,the cone-cone premium connection and the spherical-cone premium connection are selected as the research objects,and the method of combining analytical method and finite element analysis is adopted.First,the calculation formula of the contact pressure of the sealing surface of the premium connection is deduced through theory.Second,a three-dimensional finite element analysis model of the premium connection under the action of complex load and dynamic load is established to analyze the distribution rule of the contact pressure of the sealing surface and calculate the average contact pressure of the sealing surface and the contact of the sealing surface length.Finally,according to the calculation formula of sealing surface contact pressure and the results of finite element analysis,applying the theory of sealing contact energy,drawing the sealing criterion curve,only when the combined point of the average contact pressure of the sealing surface and the contact length is above the curve,the sealing performance of the premium connection is good,Based on this,the sealing criteria for premium connection are summarized.The research results show that the failure form of premium connection is mainly seal failure.According to the calculation formula of the sealing surface contact pressure derived by theory,the sealing surface taper and the sealing surface contact length can be known.The greater the taper,the longer the contact length of the sealing surface,and the better the sealing performance.From the results of finite element analysis,it can be seen that when the compound load is applied,the effect of the tensile load reduces the average contact pressure and the contact length,and the sealing performance of the premium connection slightly decreases.The effect of internal pressure makes the average contact pressure increase,the contact length increases,and the sealing performance is improved.Under the action of dynamic load,for the cone-cone premium connection,the value of the contact pressure on the sealing surface is less than the yield strength of the material,and the sealing performance is good.For spherical-cone premium connection,the value of contact pressure is greater than the yield strength of the material,and the local plastic deformation of the sealing surface has not occurred.According to the finite element calculation results,the sealing criterion of the premium connection is: when the average contact pressure of the sealing surface is 4.5 times higher than the gas sealing pressure,the premium connection has good sealing ability.