Finite Element Analysis Of Premium Connection According To ISO Procedures

ISO 13697 Petroleum and natural gas industries – Procedures for testing casing and tubing connections is a general evaluation standard for casing and tubing connections and it can be taken as an important reference for the study of the performance of premium connections.In view of the shortcomings of long life cycle and the large expense of physical full-scale test,finite element method was used in this paper to simulate each test in the standard and discuss the feasibility of simulating the physical full-scale test with the FEA method for premium connection performance evaluation.Tolerance limits was determined according to the worst-case performance objectives and the example machining tolerances in the standard,four sets of three-dimensional finite element model was established based on the geometrical parameters,through the finite element software,make-up/break-out tests were simulated.According to the CAL IV test requirements,test load,including tension,compression,internal pressure,external pressure,bending,and the load steps were calculated and designed for the test series A,B and C.Based on the designed load table,the simulation of the test load envelope tests were carried out,stress distribution and sealing performance of the premium connection under different combined load were analyzed.According to the procedure of limit load tests,structural and sealing limits of the connection under each ultimate load conditions such as ultimate tensile load and ultimate compressive load was conducted.The results show that,under the maximum make-up torque,the effective contact length of the sealing surface shortened and the sealing performance deteriorated within the increasing of seal interference.In the simulation of load envelope tests,the sealing performance was enhanced with the increasing of internal pressure;shoulders were separated because of the excessive axial tension and no longer own the auxiliary sealing effect.One side of the premium connection is pulled and the other side is pressed under the effect of bending load,seal may be failed on the press-side when the axial compression load is large.After the thermal cycling tests,the contact pressure on the sealing surface slightly decreased,but the connection still maintain a good sealing performance through the whole tests.Different dailure modes of premium connection were presented under different limit conditions,such as tripping,breaking and crushing.Stress distribution law can be obtained by simulation ISO 13679 through FEA method and can be used to further analyze the sealing performance and connection strength.This method can be used initially to provide a reference for the choice of physical test program.