CO_2对油气井管材腐蚀的预测及防护

PREDICTION AND PROTECTION OF CO_2 CORROSION OF TUBULAR GOODS IN OIL/GAS WELLS

我国华北、胜利、南海、四川、长庆、江汉等油田，有相当多的油气构造含有CO2，最高含量可达伴生气的42％，对钻杆、套管、油管和抽油杆等有很大的腐蚀作用，所以经常发生因腐蚀而造成的事矿。文中介绍了CO2对油气井管柱腐蚀的预测方法和腐蚀程度的判据。经过对一些油气田CO2腐蚀典型事故有关数据的理论计算和分析，发现实际腐蚀速率高于dewaard预测模型的计算值，其主要原因是：腐蚀井段的温度多为35～60℃，处于高腐蚀速率敏感区；地层水的Ca2+／HCO-3（单位均为meq）比值大多在0．5～1000之间，也处于高腐蚀速率区。最后，针对CO2的腐蚀环境提出了相应的防护措施。

There are quite a lot structures which contain CO2 in Huabei, Shengli, South Sea, Sichuan, Changqing, Jianghan oilfield and so on. The highest content of CO2, amounted to 42% of associated gas. This had a strong corrosivity on drill pipe, casing, tubing, sucker rod and so on. As a result, the accidents caused by CO2, corrosion often occur. This paper introduced the prediction method of CO2 corrosion and diagnosis criteria of corrosion degree.With the theoretical calculation and analysis of relevant data for typical accidents caused by CO2 corrosion in some oilfields, it was found that the actual corrosion rate is higher than the theoretical value of DE WAARD forecast model. The main reason for this is the temperature of corroded intervals is usually 35~60℃ and they are in sensitive areas with high corrosion rate. The Ca2+/HCO3- ratio of formation water (unit: meg) mostly ranges from 0. 5 to 1000 and the intervals are in high corrosion rate areas as well. In the end, the corresponding protective measures are presented in the light of corrosion environment of CO2.