Causes of Cracking In Oil Well Casing Couplings

Based on the analysis of fracture morphology, chemical composition, mechanical properties, microstructure and corrosion product composition, the causes of cracking of oil well casing ring are analyzed.


The results show that the coupling crack is mainly caused by the stress corrosion crack caused by hydrogen sulfide. After the casing enters the well, it will be exposed to hydrogen sulfide corrosion medium, which will cause serious pitting on the external surface of the coupling, forming corrosion points and pulling the coupling. The interaction between tensile stress and corrosive medium results in stress corrosion cracking of coupling. In order to prevent accidents from happening again, it is recommended to use sulfur resistant connecting materials and connect special thread to the shell.