Research on Factors Affecting Screw-off Torque of Drill Pipe Joint

Research is made on the method for calculating the screw-up torque and screw-off torque of drill pipe joint.According to relevant calculation formula,factors as affecting the screw-off torque of the drill pipe joint are summarized,based on which suggestion for increasing the screw-off torque is put forward. It is regarded via the analysis that R,the screw-off torque to screw-up torque ratio is directly related to thread lead. With the same dimensional structure,the screwof torque of the multi-line thread is smaller than that of the single-line thread. Accordingly the screw-off torque of the drill pipe joint can be increased by means of reducing the thread lead,increasing the auxiliary torque structure,increasing the friction factor of the thread compound,and optimizing the tamper,etc. Moreover it is suggested that the thread lead ratio of the premium connection be no more than 0.16,i.e.,R≥0.68.