入井深度对油管腐蚀行为的影响

Effects of Setting Depth on Corrosion Behavior of Tubing

井筒腐蚀问题关系到石油天然气工业系统安全,一直是研究热点。为找到不同入井深度油管腐蚀速率变化规律,在生产井中不同深度加装了J55钢挂片装置,正常生产6个月后取出。利用失重法测试了腐蚀速率,并对挂片微观形貌进行了分析。结果表明:在未添加缓蚀剂的油井中,下入深度为200 m时,挂片腐蚀速率平均为0.125 6 mm/a;下入深度为700 m时,挂片腐蚀速率平均为0.055 3 mm/a;下入深度为1 200 m时,挂片腐蚀速率平均为0.167 6 mm/a。添加缓蚀剂油井下入深度为200 m时,挂片腐蚀速率平均为0.029 0 mm/a;下入深度为700 m时,挂片腐蚀速率平均为0.013 4 mm/a;下入深度为1 200 m时,挂片腐蚀速率平均为0.006 8 mm/a。综合可知,在未添加缓蚀剂的油井中,J55钢腐蚀速率随下入深度的增加呈现先减少后增大的规律,沉积性保护层是引起腐蚀速率变化的主要原因;在添加缓蚀剂的油井中,J55钢腐蚀速率呈现随下入深度的增加而减小的趋势,缓蚀剂浓度变化是引起腐蚀速率差异的主要原因,添加缓蚀剂可以很好地控制油管腐蚀。

Wellbore corrosion is related to the safety of oil and gas industry system, and has been the focus of research. In the production well, J55 steel coupons were set at different depths, and then were taken out after 6 months. The corrosion rate was measured by weight loss method, and the microstructure of the coupon film was analyzed. Results showed that in the well without adding corrosion inhibitors, the average corrosion rate of the coupon was 0.125 6 mm/a at 200 m depth, 0.055 3 mm/a at 700 m depth, and 0.167 6 mm/a at 1 200 m depth. When adding inhibitors, the average corrosion rate of coupon was 0.029 0 mm/a at 200 m depth, 0.013 4 mm/a at 700 m depth, and 0.006 8 mm/a at 1 200 m depth. Without inhibitors, the corrosion rate of J55 steel decreased first and then increased with the increase of the setting depth. The sedi- mentary protective layer was the main cause for the change of corrosion rate. With inhibitors, the corrosion rate of J55 steel decreased with the increase of down depth. The concentration change of corrosion inhibitors was the main cause of corrosion rate differences. In all, the corrosion inhibitors could reduce tubing corrosion well.