中海石油(中国)有限公司天津分公司为了节能减排,在渤海湾某油田开展了天然气利用项目,天然气外输海管选用X65管线钢铺设完成.随着油田不断深入开发,天然气中CO2和H2S含量都达到了较高水平,使该海底管线在运行过程中面临潜在的不确定性腐蚀风险.因此,本文研究了在不同运行工况条件下的X65钢海管焊缝区及热影响区的腐蚀形态和腐蚀规律.试验结果表明,在管线钢的焊缝区和热影响区存在不同程度的均匀腐蚀,而点蚀相对比较轻微；试样整体均匀腐蚀速率达0.1~0.3mm/a,属于中等偏高的腐蚀程度；pH降低、温度升高会使腐蚀速率增大,在管线运行和维护过程中需针对均匀腐蚀采取控制措施.本研究可以为今后海底管线选材、焊接工艺以及后期运维等工作提供借鉴.% CNOOC (China) Limited-Tianjin carried out an offshore NG utilization project in Bohai Bay of China for energy saving and emission reduction, and API 5L X65 steel was selected for the subsea NG transmission pipeline. Whereas, CO2 and H2S content in NG is increasing along with the continuous and in-depth development of offshore oilfield, and high levels of souring gases may lead to unknown corrosion risks towards the subsea pipeline. Therefore, this paper studies on the corrosion forms and corrosion regularity of weld and heat-affected zone (HAZ) in the X65 steel pipeline under different running conditions. Results of the experiment show that uniform corrosion of varying degrees existed at both weld and HAZ, however, pitting corrosion is relatively slight. The total corrosion rate of the coupon reached 0.1-0.3 mm/a which is medium to high levels of corrosion, and the corrosion rate increased in lower pH and higher temperature in the experiment, so control measures towards uniform corrosion should be taken in its running and maintenance process. Thus, this study would be a significant reference for material selection, weld process, running and maintenance works in future.
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