油田二氧化碳驱20~#和L245NS管线钢腐蚀规律研究

Study on Corrosion Laws of Pipeline Steel 20~# and L245NS in CO_2 Flooded Oilfields

根据油田腐蚀环境,研究了Cl^-、Ca^(2+)、CO_2分压、温度和流速对20~#和L245NS两种管线钢的腐蚀影响规律。由于两种碳钢的成分相近,腐蚀速率和腐蚀规律也十分相近。两种碳钢的腐蚀速率均随温度、CO_2压力和流速的升高而增大,但随Cl^-和Ca^(2+)含量变化的规律较复杂。从电化学阻抗谱分析看,L245NS钢的耐腐蚀性能略优于20~#钢,但结合腐蚀速率和极化曲线数据发现,两种钢材的耐腐蚀性能差异甚微。在油田实际生产中,若介质平均腐蚀速率大于0.25 mm/a或点蚀率大于0.38 mm/a,这两种碳钢在应用时必须采取适当的内防腐措施。

Corrosion laws of pipeline steel 20^# and L245NS about Cl^-, Ca^2 ＋, partial pressure of CO2,temperature and flow velocity are studied in view of the oilfield corrosion environment.Because of the similar compositions of the two kinds of carbon steel, their corrosion rate and corrosion laws are also very similar. The corrosion rates of the two kinds of carbon steel both increase with the rise of temperature, CO2 pressure and flow velocity and pressure, but the change law about the content of Cl- and Ca2 ＋ is relatively complex. From the electrochemical impedance spectroscopy analysis it is know that the corrosion resistance of steel L245NS is slightly better than that of steel 20#. But com-bined with the corrosion rate and polarization curve data, the difference of the two kinds of steel in corrosion resistance is quite little. In practical oilfield production, when the average corrosion rate of the medium is more than 0.25 mm per year or the pitting corrosion rate is more than 0.38 mm per year,the two kinds of carbon steel should take appropriate anti-corrosion measures in application.