Design of an ultra-high torque double shoulder drill-pipe tool joint for extended reach wells

Abstract

Drill-pipe tool joints in extended reach wells often suffer a shear failure. In view of this, an ultra-high torque double-shoulder pipe joint was designed according to the deformation compatibility relation of the drill-pipe tool joint under torque. It is structurally characterized by long primary and secondary shoulders, small thread taper and large fillet radius of bottom tooth. First, a 3D numerical simulation model was established for this type of joint, named the XSJ joint here, based on the principle of virtual work, the Von Mises yield criterion and the nonlinear contact theory. Second, orthogonal optimization was performed on its key structural parameters by means of the orthogonal optimization method. The optimal combination of key structural parameters of the XSJ joint is taper 1:16, thread pitch 6.55 mm, guiding surface angle 29°, bearing surface angle 28°, and tooth height 3.755 mm. Finally, the bearing performance and fatigue performance of this tool joint and the API tool joint were calculated and compared using the Simulia Abaqus fe-safe software. Compared with the API tool joint, the XSJ joint is better, and its tensile strength, torsion strength, bending strength and compression strength increase by 10.65%, 62.5%, 2.75% and 52%, respectively. Its tension compression fatigue life, bending fatigue life, torsion fatigue life and composite fatigue life increase by 1.19 times, 1.74 times, 550 times and 28.79%, respectively. It is concluded that the designed XSJ joint is significantly improved in term of torsion capacity while its tension strength, bending strength and compression strength are not decreased, so it can better meet the drilling conditions of extended reach wells.