Study On Oxygen Corrosion Behavior And Mechanism Of N80 Steel

Air drive in light oil reservoir exploitation is a creative new technology during enhance oil recovery(EOR)process.However,the ground injection system and the air injection pipes are frequently subjected to severe corrosion due to high content of oxygen,resulting in the shorten of remaining life of equipment and serious security risks in oil exploitation.Besides,the corrosion problem also restricts the wide application of air drive technology.The weight-loss method,linear polarization curves,electrochemical impedance spectroscopy,energy dispersive spectrometer(EDS),X ray diffraction(XRD)and scanning electron microscopy(SEM)were used to analyze the corrosion behavior and mechanism of N80 steel in the air drive process.This paper discusses the factors affecting the corrosion of N80 steel and its corrosion mechanism,and provides the experimental and theoretical basis for the safe use of N80 steel material in a certain oilfield.Based on the mechanism of single gas corrosion,respectively according to the factors of oxygen content,temperature,and other associated gas analysis of the mechanism of oxygen of N80 steel and CO2-O2 under the condition of coexistence,interaction of corrosion of N80 steel,can be seen in its original form and mechanism with different content of oxygen and carbon dioxide content changes change obviously.The results show that the corrosion rate of N80 steel increases with the increase of O2 content,and the corrosion rate is up to 7.89 mm/a.The porous corrosion products cause the low protect ability of the matrix metal.The main component of corrosion product is Fe2O3.When O2 and CO2 coexist,the corrosion rate of N80 steel is higher than that of pure O2,which is due to the existence of CO2 and the decrease of solution Ph.Besides,the contribution of O2 to the corrosion of N80 steel is more than CO2.Similar to the pure O2 corrosion,the corrosion product film formed in the coexistence environment of O2 and CO2 is still loose and porous.The bonding force between the substrate and the base metal is low,which has no protective effect on the base metal.As a results,the composition of the corrosion product is Fe2O3.The corrosion behavior of N80 steel with temperature(25??75? 95?)was investigated at 4MPa.The results show that the corrosion rate of N80 steel increases with the increase of temperature,and the maximum value is 8.39mm/a.With the increase of temperature,the corrosion reaction is accelerated.N80 steel surface cannot form a dense corrosion product film due to the presence of O2.The results provide data support and theoretical basis for the corrosion protection of metal pipe and equipment.