集输管道CO2/油/水环境中X65钢的腐蚀特征

通过高温高压动态反应釜实验模拟油田集输管道腐蚀环境,采用腐蚀失重、X射线衍射、扫描电镜和电化学分析等方法,研究了CO₂/油/水环境中X65钢的腐蚀行为. 结果表明:不同原油含水率条件下,X65钢CO₂腐蚀形态发生改变. 含水率较低(40%~50%)时,原油的浸润作用使X65钢表面发生均匀腐蚀,局部由于原油吸附不均匀出现点蚀特征;含水率在70%~80%之间时,原油对钢表面屏障作用减弱,生成的产物膜厚而疏松、局部脱落引发台地腐蚀;含水率为90%时,台地腐蚀破坏区域扩大,腐蚀加重. 原油可以明显改变腐蚀产物晶体颗粒大小、堆垛方式、产物膜结构以及化学成分. 在原油的缓蚀作用下,X65钢CO₂腐蚀过程的温度敏感点向低温段移动,出现在50℃左右,腐蚀速率降低区间变宽,X65钢耐蚀性增强.

Corrosion characteristics of X65 steel in CO2/oil/water environment of gathering pipeline

The corrosion behavior of X65 steel in the CO₂/oil/water environment of gathering pipeline was investigated by mass loss, X-ray powder diffraction (XRD), scanning electron microscopy with X-ray microanalysis (SEM-EDS), and electrochemical analysis through dynamic reactor tests. The results indicate that the corrosion rate increases and the corrosion morphology changes with an increase in the water cut. When the water cut of crude oil is within the range 40%-50%, uniform corrosion occurs along with a lower corrosion rate due to the protection of crude oil, but pitting corrosion appears due to the inhomogeneous adsorption of crude oil. When the water cut is between 70%-80%, the barrier effect of crude oil on the steel surface is weakened, the corrosion scales become thick and loose, and the partial loss of corrosion scales cause mesa corrosion. When the water cut is 90%, the damage area of platform corrosion is enlarged. Consequently, the corrosion rate dramatically increases. Crude oil can hinder the corrosion scales from being dissolved in a corrosive medium and change the dimension and accumulation pattern of the crystal grain, thickness and structure of corrosion scales, thus influencing the corrosion rate. Under the corrosion inhibition effect of crude oil, the temperature-sensitive point of X65 steel corrosion moves to a low temperature at -50℃, lower corrosion rate interval is broadened, and the corrosion resistance of X65 steel is enhanced.