酸性油气井油套管及封隔器材料电偶腐蚀行为

GALVANIC CORROSION BEHAVIORS OF DOWNHOLE MATERIALS IN SOUR OIL AND GAS WELLS

酸性油气井油套管与封隔器的腐蚀有可能会造成严重后果,而国内对这一领域中的电偶腐蚀行为研究很少,且采用失重试验法进行的相关研究只能确定材料的腐蚀形态、类型、程度等,缺少指导性的结论。为研究该环境中电偶腐蚀的机理、影响因素及规律,预测电偶腐蚀行为,采用电化学实验法对酸性油气井中的典型低合金钢油套管材料VM80SS与作为封隔器材料的Inconel718镍基合金在四川罗家寨气田井下封隔液环境中的电偶腐蚀行为进行了研究,测量了VM80SS-Inconel718电偶对在4种不同阴阳极面积比情况下的电偶电位和电偶电流,并与失重试验法所得试验结果进行了对比分析;讨论了阴阳极面积比对电偶腐蚀的影响,得出了随着阴阳极面积比的增大,电偶电位基本呈对数增长的趋势,而电偶电流密度基本呈线性增长的结论;提出了应针对不同的电解质环境进行电偶腐蚀测量以确定腐蚀性的建议。

Serious results will be possibly caused by the galvanic corrosion on the downhole equipments like oil casing pipes and packers in those sour oil and gas wells.However,few studies can be found in present China on the galvanic corrosion behavior in this sector and so no practical reference can be obtained.Aiming at this problem,this study was carried out on the galvanic corrosion behaviors of typical low-alloy steel VM80SS as oil casing pipes and nickel-based alloy as packers under packer fluids in the Luojiazhai gas field of the Sichuan basin.An electrochemical test method was taken into use for measuring the potential and current of the Inconel 718-VM80SS couple with four different cathode/anode ratios,and the obtained results were compared with those achieved by the zero-gravity test.The effects on the galvanic corrosion by different cathode/anode ratio were discussed and galvanic potential was found to be increased logarithmically and galvanic current increased linearly with the increasing of cathode/anode area ratio.This paper suggested that the galvanic corrosion should be determined by measurement under different kinds of electrolyte environment.