Research On The Corrosion Resistance Of Cr13 Steel Serviced In Carbon Dioxide Flooding Fluid

With the development of the deep CO₂ gas reservoir,the application of CO₂ enhanced oil recovery?CO₂-EOR?makes the corrosion problem becoming more and more serious.The corrosion resistance of CO₂ shows a great influence on the safety and service life of the oil recovery system.In recent years,the high grade Cr13 stainless steel has become a research hotspot,which exhibits the characteristics of stable passivation serviced in pure CO₂ corrosion environment.At present,the research on the corrosion law and mechanism of Cr13 steel in CO₂ medium is still very limited.Therefore,the research on CO₂ corrosion resistance of Cr13 steel in CO₂ environment has become an important issue to be solved urgently in the tubing production design.In this paper,Cr13 steel was investigated by the electrochemical corrosion test method of potentiodynamic polarization,electrochemical impedance spectroscopy,and the high temperature and high pressure corrosion reaction kettle.The electrochemical and immersing behavior of Cr13 steel in produced fluid containing CO₂ were investigated.The effects of Clconcentration,temperature,flow rate and CO₂ partial pressure on the CO₂ corrosion behavior of Cr13 steel were analyzed.The corrosion products were analyzed by scanning electron microscopy?SEM?and energy dispersive spectroscopy?EDS?.The results showed that the Cr13 steel exhibited an obvious passivation behavior in the produced fluid containing CO₂,and the passive current density changed with the Clconcentration and temperature.With the increase of Cl-concentration and temperature,the passive current density increased first and then decreased,and the maximum value appeared at Cl-=60 g/L and 60 ?,respectively.The temperature was the main factor that affected the corrosion resistace of Cr13 steel under the high temperature and high pressure corrosion conditions.The influence of flow rate,CO₂ partial pressure and Cl-concentration on the corrosion of the Cr13 steel was small.In a certain temperature range,with the increase of temperature,the corrosion rate of Cr13 steel increased first and then decreased.When Clconcentration was 50g/L,the corrosion of Cr13 steel was the most serious.When the temperature reached 120 ?,the corrosion rate reached the maximum,and then the corrosion rate decreased gradually.The results of SEM and EDS showed that the main factor affecting the phenomenon was the different degree of porosity of the surface film layer.Under the same conditions,the corrosion rate of Cr13 steel was slightly higher than that of 316 L stainless steel,which was due to the lower Cr content in Cr13 steel.The pitting corrosion tendency of Cr13 steel in CO₂ medium was increased when there existed the Cl-.The actual application of Cr13 steel in transportation system containing CO₂,we should try to avoid the risk of pitting for Cr13 serviced in the medium containing Cl-.