Failure Mechanism Analysis of 5″ Weighted Drill Pipe

During the drilling operation of a well, a 5″ weighted drill pipe was fractured in the process of releasing stuck. Macroscopic morphology analysis, chemical property and mechanical properties were used to analyze the failure cause of the weighted drill pipe. The analysis results show that the failure of the weighted drill pipe is friction and wear between drill pipe and the necked borehole wall in the process of releasing the sticking. The generated wear heat reaches the phase transforms temperature of the drill pipe material, results in the “secondary heat treatment” of the drill pipe. At the same time, the high temperature reduces both the material strength and the cross section of the drill pipe. Then plastic deformation occurs in the weighted drill pipe under compression load and mud internal pressure. As a result, yield fracture occurs under load and inner pressure. It is suggested that improving the stability of wellbore, short strip and keeping the mud circulation channel unblocked are effective method to prevent drill pipe failure.