MC-2井区J55尾管腐蚀成因分析

Analysis of Corrosion Causes of J55 Liners in MC-2 Wellblock

采用水质检测、能谱分析、金相组织分析、XRD等手段,对环池油田MC-2井区J55尾管的作业介质环境、管材成分、管材组织及性能、腐蚀产物等进行了分析。结果表明,MC-2井区油井采出水的矿化度高,含有多种腐蚀性介质;H2S含量及硫酸盐还原菌(SRB)的存在造成H2S分压较高,CO2腐蚀被抑制,J55尾管的腐蚀以H2S腐蚀为主,并在最外层形成硫化铁腐蚀产物膜。介质中Cl-的作用使得H2S腐蚀膜被破坏,从而基体材料被进一步腐蚀。而且Cl-渗入腐蚀产物膜内,在基体材料内形成点蚀,加速腐蚀向基体材料内部扩展,并最终形成穿孔。

The working medium, the material composition, microstructure and performance and the corrosion products of the J55 liners used in MC-2 wellblock are analyzed through water quality testing, spectrum analysis, mierostrueture analysis and XRD. The results show that： the produced water in MC-2 wellbloek is of high salinity and there are several corrosion factors in it; the presence of H2S content and sulfate-reducing bacteria （SRB） results in high H2S partial pressure and inhibits CO2 corrosion, the corrosion of the liners is mainly H2S corrosion, and iron sulfide corrosion film is formed on the surface of the liners. The effect of Cl- makes the iron sulfide corrosion film destroyed, which leads to the matrix material of the liners further corroded. And the Cl- seeping into the corrosion product film will form pitting in the matrix material, which will accelerate the corrosion inside the matrix material and eventually form perforation in the matrix material.