Assessment of stress distribution in premium connections with ultrasonic phased array and metal magnetic memory

Abstract

The strength and sealing performance of premium connections in high temperature-high pressure (HTHP) gas well is one of the key factors for the integrity of wellbore, in which, the distribution of contact stress is the guarantee of metal-to-metal seals, while the stress distribution will affect the strength on the threaded connection. This paper explained the ultrasonic phased array (UPA) detection for contact stress of sealing surface and metal magnetic memory (MMM) detection for thread stress. The magnetic-acoustic detection test of the full-scale joints was carried out during make-up, with signals characterized the stress changes in the premium connections under the torque, the detection was also carried out during axial tension, with the contact stress of sealing surfaces quantitatively characterized by the reflection coefficient of sealing surfaces and the peak echo ratio between sealing surfaces and the inner wall of pipe. The variation of tangential component of magnetic field intensity has the same trend with that of threaded connection stress, which is linearly related to the change of contact stress in metal-to-metal seals. These findings show that the combination of UPA and MMM provides a reliable detection method for performance assessment on premium connections, both in quality control and in its field inspection.