In view of the tubing coupling failure accidents in recent years, most of the failure analysis shows that the material of the tubing nipple meets the standard of the branch company, and the main failure mechanism is tensile overload fracture, which has a great relationship with the processing quality of the tubing nipple, field operation and connection structure, especially the double male nipple connected with the tubing hanger, because the wall thickness of the tubing hanger is much larger than the nipple. It causes the stress concentration of the tubing sub section, and the connection strength is greatly reduced.
Analysis of failure law of tubing joint under stretching and other conditions. This paper expounds the law and main reasons affecting the failure of tubing sub, and determines the main factors affecting the strength of tubing joint and the control indexes of key parameters. The stress analysis of the double male joint is carried out to determine the lifting force during operation. Optimized tubing sub structure size, sub types from more than 30 to 5 basic types.
The field supplementary control method of flowline sub and tubing hanger has been studied, and the field application has achieved good results, effectively reducing the failure accident of tubing sub and improving the quality management level of tubing sub. In the study of the failure mechanism of tubing nipple, it is found for the first time that the eccentricity of the pipe end has a great influence on the joint strength of tubing nipple, which is of great value to optimize the structure of tubing nipple and improve the joint strength.
