Fracture Reason of a Deep Well Drill Pipe in Tahe Oilfield

Aiming at a typical case that S135 drill pipe fractured twice in working process, combining to the service conditions, the fracture morphology, chemical composition, mechanical properties and other properties of the drill pipe were tested. The results show that H2S partial pressure of the well exceeded 0.34 kPa, and the hardness of S135 low alloy steel drill pipe was more than 22 HCR. The fracture position was located in the tensile stress concentration position. The environmental temperature was 20-40 ℃ which is a sensitive range for sulfide stress cracking to occur. Affected by a variety of factors, H2S stress corrosion cracking formed, and resulted the fracture of S135 drill pipe.