X65碳钢的H2S/CO2腐蚀控制因素研究

目前，H₂S/CO₂腐蚀过程的控制因素判定依据主要参考Dunlop等的研究结果，但该判定结果经常与油田实际腐蚀情况不相符。为找到造成偏差的主要原因，更好地指导生产实践，采用动态高温高压釜，使用扫描电子显微镜（SEM）、能谱仪（EDS）和X射线衍射（XRD）等手段对X65碳钢在H₂S/CO₂共存体系中的腐蚀控制因素进行了研究。结果表明，不同温度下平均腐蚀速率随H₂S/CO₂分压比（p_H2S/p_CO2）的变化呈现两种不同的规律，这与腐蚀产物的膜形态和组成密切相关；腐蚀控制因素与p_H2S/p_CO2有关，而p_H2S/p_CO2临界值大小与温度密切相关。对于H₂S腐蚀控制，当温度低于40℃时，Dunlop等的研究结果仍然适用；当温度从40℃升高至60℃时，本研究的p_H2S/p_CO2临界值由0.05升高到0.10。对于CO₂腐蚀控制，本研究的p_H2S/p_CO2临界值在85℃以上时由原来的0.002逐渐升高到0.003。根据以上研究结果，修正了X65碳钢的H₂S/CO₂腐蚀过程的控制因素与p_H2S/p_CO2及体系温度的关系图。

Factors controlling H2S/CO2 corrosion of X65 carbon steel

Corrosion control factors are mainly determined based on the results of Dunlop et al., but these are often inconsistent with the actual corrosion conditions in an oil field. In order to identify the main reasons for the deviations and better guide production practice, the factors controlling the corrosion of X65 carbon steel in an H₂S/CO₂ system were studied in a dynamic high temperature autoclave, using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results showed that the average corrosion rate varied with H₂S/CO₂ partial pressure ratio (p_H2S/p_CO2), displaying two different laws at different temperatures, which are closely related to the morphology and composition of the corrosion product film. The factors controlling corrosion are related to p_H2S/p_CO2, and the critical value of p_H2S/p_CO2 is closely related to the temperature. For H₂S corrosion control, the results of Dunlop et al. are valid when the temperature is below 40 ℃. When the temperature was increased from 40 ℃ to 60 ℃ in this study, the critical value of p_H2S/p_CO2 increased from 0.05 to 0.10. For CO₂ corrosion control, the critical value of p_H2S/p_CO2 gradually increased from 0.002 to 0.003 when the temperature exceeded 85 ℃. On the basis of the above results, the relationship between the factors controlling the H₂S/CO₂ corrosion process in X65 carbon steel and p_H2S/p_CO2 and system temperature can be reformulated.