Optimization Design of the Non-magnetic Drill Rod for Directional Drilling in the Coal Mine

A beryllium-copper no-magnetic drill rod was designed for directional drilling. Through the stress analysis of the joint thread, the finite element contact analysis of the joint thread was carried out by using ANSYS Workbench finite software. According to the working characteristics of directional drilling, the structure of non-magnetic drill rod joint was optimized, which has reduced the stress of joint by 20.8%, the contact stress decreased by 16.3% along the axis of the joints, which greatly improved the torsion resistance and fatigue capacity of the threaded joints. Finally, the beryllium-copper non-magnetic drill rod was verified by downhole industrial test, and no joint fracture or expansion buckle occurred in the drill rod, which shows that the structural optimization design of the drill rod joints is reasonable.