Research On Gas-sealing Capacity Of Tube Thread With The Action Of Axial Tension

In this paper the phenomenon of gas leakage of natural gas well in Jilin Oilfield has been studied, which found that the position of gas leakage is mainly located in tube thread. During the process of operation, downhole strings are often influenced by the functions of stretching, curving, temperature and so on, which usually have accidents of thread gluing, slipping, breaking, corrosion and so on. These accidents make the integrity of joints destructive and lead natural gas well to leak. Thus, to solve the question of gas leakage of natural gas well, it is necessary to have the mechanical analysis at the position of thread.In this paper by combining the research materials of scholars at home and abroad, the main elements of affecting the loading capacity of tube thread have been studied and the influences of axial tension on the loading capacity of tube has been regarded as the research object of this paper. First of all, to the ordinary thread that is sealed based on the interference matching between thread teeth, the radial contact force model of tube thread with axial tension has been established to judge the influences of axial tension on the loading capacity of tube thread. To unusual threads that are sealed based on torque shoulder, the Von Mises stress and contact stress analysis of sealing contact surface of BGT and FOX has been conducted by using ANSYS software to judge the influences of axial tension on contact stress and Von Mises stress. The changing laws of loading capacity of BGT and FOX have been tested with the changing of axial tension. By combining the laboratory findings and ANSYS analysis results, the relationship between loading capacity and contact compressing stress of sealing surface has been determined.