Simulation analysis of flow field and shear stress distribution in internal upset transition zone of drill pipe

Perforation in internal upset transition zone is one of the main failure styles for drill pipes. Due to the flow channel specificity of upset transition zone, in this paper, drill pipe failure analysis from the point of flow erosion was put forward. Flow field of drilling fluid in the internal upset transition zone of Φ127 mm API IEU S135 drill pipe under various conditions were obtained using finite volume CFD solver FLUENT 13.0. Pressure, velocity and wall shear stress distribution in upset transition zone indicated the erosion of flowing fluid on drill pipe. The type and displacement of drilling fluid and the structure of internal upset transition zone exert great effects on the flow field. Under the same displacement of drilling fluid, mud shows the most severe erosion effect. And the larger the displacement, the more obvious is the washout. An increase in length or radius of the transition can weaken the flow erosion.

► A numerical procedure is employed to study the flow erosion in upset transition zone of drill pipe.
► Flow field has an obvious change in transition zone near box thread, inducing the pipe failure.
► Effects of drilling fluid and displacement on flow erosion were described.
► Structural optimization analysis was carried out to reduce the flow erosion.