表面缺欠对超级13Cr油管在气井酸化过程中的腐蚀行为影响研究

目的研究光滑表面、无缺欠原始表面和带缺欠原始表面13Cr油管试样在气井酸化增产改造过程中的腐蚀行为,明确不同表面状态对超级13Cr油管腐蚀行为及机理的影响。方法采用高温高压腐蚀模拟实验,研究了三种表面状态的超级13Cr油管在气井酸化过程中鲜酸和残酸环境下的腐蚀行为。分别通过宏观观察、扫描电镜、三维共聚焦显微镜分析了试样在鲜酸和残酸中腐蚀后的宏观、微观和三维形貌。结果在鲜酸溶液中,无缺欠原始表面试样和带缺欠原始表面试样腐蚀速率相当,但均明显高于光滑表面试样。在残酸溶液中,缺欠导致超级13Cr油管腐蚀速率显著增大,带缺欠原始表面试样的腐蚀速率是,是无缺欠原始表面试样的2倍,光滑试样的7.3倍。结论超级13Cr油管表面状态对其在气井酸化过程中的平均腐蚀速率和局部腐蚀有显著的影响,内表面缺欠会降低其在酸化过程中的耐蚀性能,且此类缺欠对残酸介质更为敏感。

Influence of Surface Imperfection on Corrosion Behavior of 13Cr Tubing in Gas Well Acidizing Process

The work aims to investigate the influence of surface imperfection on corrosion behavior and mechanism of 13Cr tubing in gas well acidizing process by studying corrosion behavior of super 13Cr tubing samples with smooth surface, nondefective surface and defective surface in gas well acidizing and capacity increasing revamp process. High temperature high pressure simulation experiment was completed to study the corrosion behavior of as-received tubing samples in three conditions gas well acidizing process in live and spent acid. Macro-, micro- and 3D morphology of the samples being corroded in live and spent acid was analyzed with optical microscope, SEM, and 3D confocal microscope. In live acid, corrosion rate of nondefective as-received surface sample was almost equal to that of defective as-received surface sample, but corrosion rate of smooth surface sample was much lower. In spent acid, corrosion rate of the nondefective as-received surface sample was 7.3 times of that of the smooth surface sample, and 2 times of that of the nondefective as-received surface sample. Surface state of super 13Cr tubing has a substantial influence on its average corrosion rate and local corrosion rate in gas well acidizing process, imperfection on internal surface reduces corrosion resistance of 13Cr tubing in both acidizing processes. Moreover, such imperfection has a greater influence on 13Cr tubing corrosion in spent acid than that in live acid.