Mechanical Characteristics Of Expandable Casing Connection Metal Seal During Expansion

As the key link of this technology,expansion casing joint is prone to fracture and leakage after expansion deformation,which is the main difficulty restricting the development of this technology.In this paper,the metal seal structure of the expandable casing connection is taken as the research object.The two-dimensional axisymmetric model of the expandable casing connection is established by finite element analysis method.The deformation of the metal seal structure of the expandable casing connection during the expansion process and the contact force between the sealing surfaces after expansion are mainly concerned.The expansion process of the expandable casing connection is simulated by LS-DYNA.The influence of tool friction coefficient,sealing surface taper and sealing surface interference on the sealing performance of the connection after expansion is studied,which provides reference for the design of metal seal structure of the expandable casing connection.The main conclusions of the paper are as follows:(1)The greater the tool friction coefficient,the greater the reduction of the thickness of the metal sealing surface of the external thread joint,the smaller the shortening of the width of the metal sealing surface of the internal thread joint,the greater the contact force between the metal sealing surface after expansion,the more conducive to sealing;Excessive tool friction coefficient leads to structural failure of the connection during the process.(2)The smaller the taper of the sealing surface,the greater the reduction in the thickness of the metal sealing surface of the external threaded joint,the smaller the reduction in the width of the metal sealing surface,the greater the contact force between the metal sealing surfaces after expansion.Therefore,choosing a smaller taper of the metal sealing surface is more conducive to the realization of the sealing effect.(3)The interference amount of sealing surface has little influence on the thickness change of sealing surface.The greater the interference amount of sealing surface,the greater the shortening amount of the metal sealing surface width of the internal and external threaded joint,the greater the contact force between the expanded metal sealing surfaces,and the more conducive to sealing.