油套管在CO_2和H_2S共存时的腐蚀机理研究

The Experiment Research of A Corrosion Mechanism about the Tube in CO_2 and H_2S Environment

采用模拟高温高压CO2、H2S共存时的腐蚀试验及腐蚀产物膜的分析方法,研究了井下高温高压CO2、H2S共存时NT80SS油管腐蚀膜的特征及其对电化学腐蚀的影响。结果表明:在H2S、CO2和Cl-共存条件下,气相区高温静态腐蚀表现为垢下腐蚀;在液相区则以均匀腐蚀为主,腐蚀的发生是H2S和CO2共同作用的结果,其机理可能是CO2在液相中与钢先发生作用生成FeCO3,H2S在液相中与FeCO3反应生成了更为稳定的FexSy,在液相中,FexSy吸附层对离子的迁移起到了部分的阻拦作用。由于在气区的垢下腐蚀为局部腐蚀,腐蚀速度大于液相区的腐蚀。

The paper studied the simulated NT80SS tube corrosion product layer and the weight-loss corrosion in the autoclave downhole CO_2 and H_2S environment. The conclusion is reached that the nature of tube corrosion in vapor phase is scale corrosion and general corrosion prevails in the solution containing H_2S,CO_2 and Cl^-. The H_2S and CO_2 play different roles in the corrosion process: the FeCO_3 is formed due to CO_2 in the solution react to Fe, and the FeCO_3 reacts to H_2S in the solution to produce the more stable Fe_xS_y. Some of the Fe_xS_y baffle the transition of ions for corrosion action in the solution. The average corrosion rate in vapor phase is greater than in the solution because the corrosion in a vapor is the local corrosion under scale.