The simulation analysis of sealing performance of cone-cone premium tubing connection under combined loads

Abstract

Under the complex downhole loads, premium tubing connections often suffer from seal failure and threaded connection failure, leading to tubing string leakage and even safety accidents. Therefore, this paper focuses on the cone-cone premium tubing connection, simulating the make-up process and downhole load conditions, establishing three dimensional finite element models of premium tubing connections, analyzing the distribution of equivalent stress and contact pressure on sealing surface, shoulder and thread. The results show that the stress is mainly concentrated on the shoulder and sealing surface under the make-up torque. The equivalent stress on the shoulder shows a trend of increasing first and then stabilizing. The equivalent stress at the sealing surface tends to be stable first and then decreases. Under the combined loads, the overall equivalent stress of connection increases. The contact pressure decreases slightly in the area of sealing surface and the shoulder inflection point. It may cause joint failure and leakage, when the internal pressure is over 80MPa and the axial compressive load is greater than 800kN, which will lead to the maximum equivalent stress of the threaded part exceed 5.5% of the yield strength.