某油田输油螺旋焊缝管内壁腐蚀带的成因分析

    Cause Analysis on Corrosion Zone on Inner Wall of Oil-carrying Spiral Welded Pipelines in An Oilfield

    • 摘要: 尽管某油田输油管道内液体介质含水率较低(< 1%),但内检时发现该螺旋焊缝管内壁存在局部分布的腐蚀带。为此,针对管材、腐蚀产物,开展了理化性能检测、扫描电镜及能谱分析,以明确腐蚀带的形成原因,并对此管道进行剩余强度评价及防腐策略制定。结果表明:管材母材C、Mn元素含量及抗拉强度不符合标准要求,腐蚀原因主要是垢下腐蚀;同时,输送介质中存在微量的水,且水中含有S和Cl-,因而进一步促进腐蚀。此管道在内壁腐蚀的情况下可以安全运行,但应及时开展管道内输送介质的腐蚀性监测,并采用定期清管或加注缓蚀剂等措施,以防止或减弱该螺旋焊缝管的内壁腐蚀倾向。

       

      Abstract: Although the water content of the liquid medium in oil pipeline of a certain oilfield is relatively low (<1%), it was found during internal inspection that there are locally distributed corrosion zones on the inner wall of the spiral welded pipe. Therefore, physical and chemical performance testing, scanning electron microscopy and energy spectrum analysis were carried out for the pipe and corrosion products to clarify the causes of corrosion bands, and residual strength evaluation and anti-corrosion strategy formulation were carried out for this pipeline. The results show that the content of C and Mn elements of the pipe base material and the tensile strength does not meet the standard requirements. The main cause of corrosion is corrosion under scale. At the same time, due to the presence of trace amounts of water in the conveying medium and the presence of S and Cl - ions in the water, corrosion is further promoted. This pipeline can operate safely in the event of corrosion on the inner wall, but timely monitoring of the corrosivity of the medium transported within the pipeline should be carried out, and measures such as regular cleaning or adding corrosion inhibitors should be taken to preventor reduce the tendency of corrosion on the inner wall of the spiral welded pipe.

       

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