Investigation on impact absorbed energy index of drill pipe

Drill pipe is one of the most important tools for petroleum and natural gas drilling exploitation. The application of S135 drill pipe can significantly increase drilling depth, reduce drilling cost and improve drilling quality. Impact absorbed energy is the most important toughness index, which has a decisive influence on the service safety of drill pipe. The statistical results of 91 drill pipe failure cases show that the piercing is the main failure mode of S135 drill pipe, including oval-shaped piercing and slot piercing. The length of oval-shaped piercing hole is mainly distributed in 20–50 mm, and the impact absorbed energy of failed drill pipe is dispersed in 42–156 J. The length of slot piercing hole is mainly distributed in 60–90 mm, and impact absorbed energy of failed drill pipe is concentrated in 76–150 J. Analysis results show that there is certain correlation between the length of piercing hole and impact absorbed energy values of drill pipes. In this work, the impact absorbed energy index calculation formula of “leakage before fracture” failure mode for drill pipe is proposed. The results show that the impact absorbed energy value increases with the increasing of critical crack length, square of stress strength coefficient and strength level. The impact absorbed energy value of S135 drill pipe should be greater than 80 J to ensure the service safety.