PREDICTION AND PROTECTION OF CO2 CORROSION OF TUBULAR GOODS IN OIL/GAS WELLS

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.