川西气田P110钢孔蚀行为研究

发布时间：2018-04-25 03:30

本文选题：孔蚀 + 亚稳孔　；参考：《西南石油大学》2015年硕士论文

【摘要】：P110钢是川西气田油套管使用的主要材料,局部腐蚀穿孔是川西气田P110油套管腐蚀破坏的主要形式。油套管的腐蚀穿孔,给气田生产带来了安全隐患,川西气田的正常生产与持续开发受到了严重的影响。因此,研究P110钢在川西气田腐蚀环境下的孔蚀行为及其影响因素,理解其孔蚀机理,总结各因素对P110钢孔蚀行为的影响规律,为川西气田P110油套管的合理使用及腐蚀防护提供了理论基础,具有重要的理论意义和实用价值。本文结合川西气田现场实际腐蚀背景资料,综合应用电化学测试方法、扫描电子显微镜观察、统计学等多学科方法,研究了P110钢在川西气田腐蚀环境下孔蚀早期即亚稳态孔蚀期间的电流波动现象及其电化学特征；分析了温度、Cl-浓度、HCO3-浓度及SO24-浓度对P110钢孔蚀行为的影响规律；研究了缓蚀剂作用下P110钢的孔蚀行为。主要结论如下： (1)在发生稳定孔蚀前,P110钢的电流波动曲线上会出现小幅度的有规律的电流波动,每一个电流波动峰是亚稳态小孔形核、生长及再钝化的过程。亚稳态孔蚀的萌生虽然具有很大的随机性,但亚稳孔出现电位Em的大小具有一定规律,实验结果表明,亚稳孔出现电位Em服从正态分布。 (2)动电位下,电位的增加将造成P110钢亚稳孔的形核数目增多,亚稳孔的平均生长速度加快,亚稳孔平均峰值电流增大,亚稳孔寿命也会变长。P110钢在亚稳态孔蚀期间,表面蚀孔活性点溶解较慢,亚稳孔生长较慢,而亚稳孔的再钝化过程则比较迅速。当腐蚀产物覆盖在小孔表面,在小孔内形成闭塞电池后,亚稳态小孔逐步转变为稳定孔。 (3)温度、C1-浓度、HCO3-浓度和SO24-浓度这4个因素中,温度对P110钢孔蚀行为的影响高度显著,Cl-浓度和SO24-浓度对P110钢孔蚀行为的影响显著,HCO3-浓度对P110钢孔蚀行为的影响有显著,这4个因素对P110钢孔蚀行为影响大小排序为：温度Cl-浓度SO24-浓度HCO3浓度。 (4)添加缓蚀剂H后,P110钢的点蚀电位大大正移,其容抗弧半径也大大增加,缓蚀剂H能有效抑制P110钢孔蚀的发生,且缓蚀剂浓度达到100mg/L时达到了最佳缓蚀效果,缓蚀率高达91.23%,缓蚀效果能够满足现场的要求。
[Abstract]:P110 steel is the main material used in oil casing in western Sichuan gas field, and local corrosion perforation is the main form of corrosion failure of oil casing in western Sichuan gas field. The corrosion and perforation of oil casing has brought safety hidden trouble to gas field production, and the normal production and sustainable development of western Sichuan gas field have been seriously affected. Therefore, the pitting behavior of P110 steel in the corrosion environment of western Sichuan gas field and its influencing factors are studied, the pitting mechanism of P110 steel is understood, and the influence law of various factors on pitting corrosion behavior of P110 steel is summarized. It provides a theoretical basis for the rational use and corrosion prevention of P110 oil casing in western Sichuan gas field, and has important theoretical significance and practical value. In this paper, based on the actual corrosion background data in western Sichuan gas field, the methods of electrochemical measurement, scanning electron microscope observation, statistics and other multidisciplinary methods are comprehensively applied. The current fluctuation and electrochemical characteristics of P110 steel in the early stage of pitting corrosion, i.e. during metastable pitting, were studied, and the influence of temperature and concentration of Cl-HCO3- and SO24- on pitting corrosion behavior of P110 steel was analyzed. The pitting corrosion behavior of P110 steel under the action of corrosion inhibitor was studied. The main conclusions are as follows: (1) the current fluctuation curve of P110 steel before the stable pitting corrosion occurs a small amplitude of regular current fluctuation, each current fluctuation peak is the process of metastable pore nucleation, growth and repassivation. Although the initiation of metastable pitting corrosion is very random, the magnitude of the metastable pore occurrence potential E _ m has a certain regularity. The experimental results show that the metastable pore potential E _ m appears from the normal distribution. 2) under dynamic potential, the number of metastable pore nucleation will increase, the average growth rate of metastable pore will accelerate, the mean peak current of metastable pore will increase, and the life of metastable pore will also become longer during metastable pitting corrosion of P110 steel. The active point of surface etching is slower to dissolve, the metastable pore grows slowly, and the metastable pore is repassivated rapidly. When the corrosion product is covered on the surface of the pore and the occluded cell is formed in the pore, the metastable pore is gradually transformed into a stable pore. Among the four factors, the influence of temperature on pitting corrosion behavior of P110 steel is highly significant. The effect of Cl- concentration and so _ 24- concentration on pitting corrosion behavior of P110 steel is significant. The effect of HCO3- concentration on pitting corrosion behavior of P110 steel is significant. The order of influence of these four factors on pitting corrosion behavior of P110 steel is as follows: temperature Cl-concentration SO24- concentration HCO3 concentration. (4) the pitting potential of P110 steel after adding inhibitor H is greatly positive, and its arc resistance radius is also greatly increased. The corrosion inhibitor H can effectively inhibit the pitting corrosion of P110 steel, and the best corrosion inhibition effect is achieved when the concentration of inhibitor reaches 100mg/L. Corrosion inhibition rate up to 91.23, corrosion inhibition effect can meet the requirements of the site.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE983

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