根据我国海上某油田L80-3Cr油管服役环境,利用失重法研究二氧化碳分压、腐蚀介质流速和腐蚀介质气液比例对油管材料腐蚀速率的影响。试验发现,随着二氧化碳分压增大,L80-3Cr腐蚀速率先增大后减小,在二氧化碳分压为3.0 MPa时达到最大腐蚀速率。对最高腐蚀速率试样表面的SEM观察和XRD分析表明,试样表面形成的腐蚀产物膜主要由碳酸亚铁组成,膜层致密性差和疏松多孔是导致高腐蚀速率的主要原因。在低流速腐蚀介质中,L80-3Cr腐蚀速率较小,高流速下,L80-3Cr腐蚀速率快速增加。气液两相流流经试样表面使得材料腐蚀加剧,随着腐蚀介质中含气量的增加试样腐蚀速率先增大,在气液比增加到0.227之后略有下降。通过电化学测试评价了油田常用的混合型缓蚀剂,随着添加缓蚀剂浓度的增加,缓蚀效率略有增大,缓蚀剂主要通过在金属溶液界面吸附成膜,增大腐蚀反应的极化电阻从而抑制腐蚀发生。
In view of the working environment of the L80-3Cr tubing in an offshore oilfield in China，the weight loss method was employed to study the effects of carbon dioxide partial pressure，corrosive medium flow rate and corrosive medium gas-liquid ratio on the corrosion rate of tubing materials.Results showed that as the partial pressure of carbon dioxide increased，the corrosion rate of L80-3Cr increased firstly and then decreased，which reached the maximum when the partial pressure of carbon dioxide was 3.0 MPa.The results of SEM observation and XRD analysis on the surface of the sample possessing the highest corrosion rate showed that the corrosion product film formed on the surface of the sample was mainly composed of ferrous carbonate，and the poor film compactness and loose porosity were the main reasons for high corrosion rate.In corrosive medium with low flow rate，the corrosion rate of L80-3Cr was relatively small.However，the corrosion rate of L80-3Cr increased rapidly in high-velocity corrosion medium.Furthermore，gas-liquid two-phase flow passing through the surface of the sample could increase the corrosion rate of the material.With the increase of the gas content in the corrosive medium，the corrosion rate of the sample increased firstly，and then decreased slightly after the gas-liquid ratio increased to 0.227.Besides，the performances of hybrid corrosion inhibitors commonly used in oilfields were evaluated by electrochemical tests.The inhibition efficiency increased slightly with the increase of the concentration of corrosion inhibitor.The corrosion inhibitor mainly inhibited the occurrence of corrosion by adsorbing the film at the interface of the metal solution to enhance the polarization resistance of the corrosion reaction.
