海上W油田P110保温油管腐蚀行为的试验研究

Experimental Study on the Corrosion Behavior of Insulated Tubing Made of P110 Steel in Offshore W Oilfield

目前对P110保温油管在高含CO_(2)气体分压的井筒中的腐蚀情况研究较少;主要考虑CO_(2)分压与温度影响,较少考虑腐蚀介质含水率的影响;腐蚀试验周期一般在120 h以内,较短的试验周期容易造成腐蚀速率测试结果偏高,且目前较少有P110钢腐蚀速率的预测模型。为此,模拟油田腐蚀环境,通过高温高压反应釜动态旋转挂片法进行腐蚀试验,借助SEM形貌观察及XRD物相分析等手段研究了温度、CO_(2)分压、腐蚀介质流速、含水率等因素对P110保温油管腐蚀行为的影响。结果表明:低温条件下腐蚀产物结构松散,容易脱落,对基体保护效果较差,以全面腐蚀为主;80℃时腐蚀产物膜较厚,含有较多的孔洞与缝隙,局部腐蚀作用明显;高温条件下产物膜由较规则的晶粒组成,致密均匀,对基体有较好的保护作用,为全面轻度腐蚀。腐蚀速率随温度升高先增加后减小,80℃时腐蚀速率出现极值4.73 mm/a;随CO_(2)分压的升高呈线性关系增加;随着腐蚀介质流速的增加指数关系增大;随腐蚀介质含水率的升高呈平方关系增大。基于试验结果,建立了多因素腐蚀速率预测模型,可为工程上P110保温油管腐蚀速率预测提供参考。

At present,there is little research on the corrosion of P110 insulating tubing in the wellbore with high CO_(2) partial pressure.Previous studies mainly considered the influence of CO_(2) partial pressure and temperature,less considered the influence of water content of corrosive medium;Generally,the corrosion test period was less than 120 h.The short test period was easy to cause the high corrosion rate test results,and there were few prediction models for the corrosion rate of P110 steel.Therefore,the corrosion environment of oil field was simulated,the corrosion test was carried out by high temperature and high pressure reactor dynamic rotating coupon method.The effects of temperature,CO_(2) partial pressure,corrosion medium flow rate and water content on the corrosion behavior of P110 insulating tubing were studied by means of SEM morphology observation and XRD phase analysis.Results showed that the corrosion product structure was loose and easy to fall off at low temperature,and the protection effect on the matrix was poor,which was mainly full corrosion.The corrosion product film was thicker at 80℃,with more holes and crevices,and the local corrosion effect was obvious.At high temperature,the product film was composed of regular grains,the product film is compact and uniform,and had better protection effect on the matrix,which was overall mild corrosion.The corrosion rate increased first and then decreased with the increase of temperature,and reached an extreme value of 4.73 mm/a at 80℃.Furthermore,the corrosion rate increased linearly with the increase of partial pressure of CO_(2),and increased exponentially with the increase of flow rate of corrosive medium;and increased squarely with the increase of water content of corrosive medium.Based on the experimental results,a multi-factor corrosion rate prediction model was established,which could provide a reference for the prediction of corrosion rate of P110 insulating tubing in engineering.