Fracture Failure Analysis of 127mmG105 Drill Pipe

The failure cause of one Phi 127mm G105 drill pipe was investigated through mechanical properties testing, optical morphologies and fracture analysis. The results show that drill pipe's failure reason is the "martensite" white bright layer in its out-surface caused by intense friction in drilling process. Under the effect of torque and tensile loads, lots of cracks initiated in the white bright layer and developed along the vertical. In the end, when its tensile capacity was less than the weight of drilling string, drill pipe fractured along the horizontal. In addition, H2S in the travelling environment promoted crack's initiation and development.