海上某油田井下支管发生腐蚀穿孔，结合腐蚀环境、管柱结构、腐蚀产物分析以及电化学测试等，综合分析了支管腐蚀穿孔原因，并对其腐蚀机理做了推断。结果表明：导致井下支管腐蚀的原因为支管和套管间缝隙的缝隙腐蚀。最后有针对性地提出了解决措施，以期为解决油田类似腐蚀问题提供借鉴。

The downhole pipe of a sea oilfield has corrosion perforation. In combination with the analysis of corrosion environment, pipe string structure, corrosion product, and electrochemical testing, the reasons and mechanision of the branch pipe corrosion perforation were analyzed. The results showed that the cause of the downbole pipe corrosion was the crevice corrosion between branch pipe and casing gap. Finally, the the solving measures to provide the reference for similar oilfield corrosion problems were put forward.