Influence of Working Height of a Thread Profile on Quality Indicators of the Drill-String Tool-Joint

Abstract

Drilling oil and gas wells is always accompanied by the process of screwing and unscrewing the drill-pipe connector. Its effectiveness largely depends on the accuracy and quality of the thread profile, including the profile height’s accuracy. Studies show a decrease in the contact pressures and stresses between the threaded surfaces of the box and the pin of the drill string tool-joint as the working height of the profile increases. It is a positive factor influencing the durability and reliability of the drill pipe connector. On the other hand, the same increase of the working height leads to the improvement of the screwing process itself, which is an integral part of lowering and lifting operations during the operation of drill strings. The increased contact area allows the joint to handle high make-up torques without damaging the thread profile. It is also advisable to consider the design of the roots not of around but of an elliptical profile. To ensure leak-tightness and fatigue strength, the operation of joints with a reduced value of h should be avoided.