Failure Analysis on Cracking of G105 Drill Pipes in a Well

The batch cracking causes of G105 drill pipes in a well were analyzed by means of macro observation, chemical composition analysis, metallographic analysis, mechanical property test, scanning electron microscope and energy spectrum analysis and so on. The results show that the hardness of the drill pipe reached 33 HRC which was much higher than the required value of MR NACE 0175-2009 (≤22 HRC) for the sulfide stress corrosion cracking (SSCC) resistant material, so the SSCC susceptibility of the drill pipes was very high. The cracking of the drill pipes was brittle cracking mainly caused by the hydrogen sulfide stress corrosion, and at the same time CO₂ and Cl^-1 in the well accelerated the corrosion process. It was suggested that anti-sulfur drill pipes should be used in the environment containing H₂S gas to effectively prevent the drill pipes from hydrogen sulfide stress corrosion cracking.