阿姆河右岸异常高压含CO2气田采气井口节流管段的腐蚀失效分析

Corrosion failure analysis of gas pipe on the gas wellhead in the Right Bank of the Amu Darya River

关键词:  酸性气田  气井节流管段  CO₂腐蚀  冲蚀

Key words:  sour gas field  throttling pipe section of gas well  carbon dioxide corrosion  erosion

摘要:

阿姆河右岸B气田采输管道内CO₂分压0.6 MPa,采气井口节流管段的内壁腐蚀严重。对腐蚀管件进行电镜扫描、能谱分析、XRD组分分析、金相分析、硬度分析和动态分析。结果 表明:腐蚀管件硬度满足材料性能要求,腐蚀产物主要成分为FeCO₃,含有Ba和Si 等其他成分;管件失效的主要原因是天然气中的CO₂在适宜温度、含水的条件下导致碳钢管道内壁发生电化学腐蚀反应,节流效应导致流体形成强大的冲刷作用,缓蚀剂无法在节流管段内壁形成保护膜,腐蚀产物难以附着成膜;流体自井底携带的泥砂加剧了对节流管段的冲蚀作用,管道内壁的金属暴露在腐蚀环境中,腐蚀速率将大大增加。提出了采用耐腐蚀合金堆焊材料的治理建议。 

Abstract:

The CO₂ partial pressure in the B gas field on the right bank of the Amu Darya River is 0.6 MPa, and the inner wall of the throttling section of the gas production wellhead is seriously corroded. Electron microscopy, energy spectrum analysis, XRD composition analysis, metallographic analysis, hardness analysis and dynamic analysis were carried out. The results show that the main component of corrosion is FeCO₃, containing other components such as Ba and Si. The hardness of the corroded pipe meets the material performance requirements, and natural gas contains acidic components such as CO₂. The main reason for the failure of the pipe is that the CO₂ in the natural gas leads to electrochemical corrosion on the inner wall of the carbon steel pipe under suitable temperature and humid conditions, and the throttling effect causes a strong scouring effect of the fluid, contributing to the failure of the formation of protective film on the inner wall of the throttling pipe section by corrosion inhibitor, with the difficulty of corrosion product to form a complete film. The sediment carried by the fluid from the bottom of the well intensifies the erosion of the throttling pipe section, which forms an erosion pit, and the metal of the inner wall of the pipe is exposed to a corrosive environment, increasing the corrosion rate greatly. Suggestions for the treatment of corrosion-resistant alloy surfacing materials have been proposed.