油田埋地碳钢管道外腐蚀行为研究

针对大庆油田龙虎泡作业区埋地碳钢管道外腐蚀较为严重的情况，通过检测埋管防护层破损点周围土壤的物理、化学性质和硫酸盐还原菌（SRB）数量，分析土壤的腐蚀性。采用扫描电镜能谱（SEM-EDS）、X射线衍射（XRD）和红外光谱（IR）等技术对管道外壁腐蚀物的形貌、元素组成和矿物成分等进行了表征和分析。借助动电位极化曲线和电化学阻抗谱（EIS）进一步研究了埋地碳钢管道外壁在土壤浸出液中的腐蚀行为。结果表明，作业区潮湿的盐碱性土壤环境和复杂多变的土壤性质使该地区埋地碳钢管道发生腐蚀；腐蚀产物主要包括Fe₃O₄和FeOOH，其中FeOOH位于外层，Fe₃O₄位于内层；腐蚀产物通过参与阴极反应或充当大阴极来加剧管道腐蚀。

External Corrosion of Buried Carbon Steel Pipelines in Oilfields

With regard to the relatively severe external corrosion of buried carbon steel pipelines in the Longhupao operation zone of the Daqing Oilfield, soil corrosivity was analyzed by determining the physical properties, chemical properties, and counts of sulfate-reducing bacteria of soil around coating defects on the buried pipelines. The morphology, elemental composition, and mineral content of corrosion products on the external walls of the pipelines were characterized and analyzed using techniques such as scanning electron microscopy-energy dispersive x-ray spectrometry, x-ray diffraction, and infrared spectroscopy. By means of potentiodynamic polarization curves and electrochemical impedance spectroscopy, the corrosion behavior on the external walls of buried carbon steel pipelines in soil extract solution was further investigated. The results indicated that the corrosion of buried carbon steel pipelines in the zone was caused by the wet saline-alkali soil environment as well as complex and varying soil properties. The corrosion products were mainly Fe₃O₄ and FeOOH, located in the inner and outer layers, respectively. The corrosion products contributed to cathodic reactions or acted as large cathodes, further aggravating pipeline corrosion.