Abstract
In the research, the corrosion and mechanical properties, as well as susceptibility to hydrogen embrittlement, of two casing pipe steels were investigated in order to assess their serviceability in corrosive and hydrogenating environments under operation in oil and gas wells. Two carbon steels with different microstructures were tested: the medium carbon steel (MCS) with bainitic microstructure and the medium-high carbon steel (MHCS) with ferrite–pearlite microstructure. The results showed that the corrosion resistance of the MHCS in CO2-containing acid chloride solution, simulating formation water, was significantly lower than that of the MCS, which was associated with microstructure features. The higher strength MCS with the dispersed microstructure was less susceptible to hydrogen embrittlement under preliminary electrolytic hydrogenation than the lower strength MHCS with the coarse-grained microstructure. To estimate the embrittlement of steels, the method of the FEM load simulation of the specimens with cracks was used. The constitutive relations of the true stress–strain of the tested steels were defined. The stress and strain dependences in the crack tip were calculated. It was found that the MHCS was characterized by the lower plasticity on the stage of the neck formation of the specimen and the lower fracture toughness than the other one. The obtained results demonstrating the limitations of the usage of casing pipes made of the MHCS with the coarse-grained ferrite/pearlite microstructure in corrosive and hydrogenating environments were discussed.
Highlights
Steel casing pipes are the main mechanical structural barrier elements during oil and gas oilfield lifecycle and beyond
A method based on an finite element method (FEM) calculation using the true stress–strain diagrams has been effectively utilized in various aspects of assessing the mechanical behavior of structural materials, in particular, to study the operational degradation of pipe steels of gas transit pipelines [12,24] and casings [23]
Two carbon steels of casing pipes that are used in oil and gas wells in Ukraine were investigated: the medium carbon steel (MCS, the grade 50 steel, Ukrainian code) and the medium–high carbon steel (MHCS, the grade 32H2 steel, Ukrainian code)
Summary
Steel casing pipes are the main mechanical structural barrier elements during oil and gas oilfield lifecycle and beyond. Since hydrogen evolution is possible during electrochemical corrosion of a metal in acidic solutions, the susceptibility of a casing steel to hydrogen embrittlement, stress corrosion cracking, and corrosion fatigue is important for assessing the integrity issues for casing [5,17] Dissolved gases such as oxygen O2, carbon dioxide CO2, and hydrogen sulfide H2S have a decisive influence on the corrosivity of an environment [14,18]. A method based on an FEM calculation using the true stress–strain diagrams has been effectively utilized in various aspects of assessing the mechanical behavior of structural materials, in particular, to study the operational degradation of pipe steels of gas transit pipelines [12,24] and casings [23]. To estimate the embrittlement of steel, FEM calculations were used, taking into account the true stress–strain relationships
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
