气体钻井井口腐蚀(冲蚀)检测装置设计与应用

Design and Application of the Wellhead Corrosion(Erosion) Detection Device for Gas Drilling

为了提前预知气体钻井工况下可能引起的腐蚀(冲蚀)危险,研制了适用于气体钻井的井口腐蚀(冲蚀)检测装置。该装置克服了现有技术的不足,安装在气体钻井排砂管线(或测试管线)上,可快速真实监测气体钻井腐蚀(冲蚀)速率,为现场实施气体钻井提供指导,降低井控风险。现场监测结果表明,用该装置测得S135腐蚀棒的平均腐蚀(冲蚀)速率为9.5 mm/a,其表面光滑,局部有细小凹坑,属于典型的高速气流携带钻屑的冲蚀行为;P110腐蚀棒平均腐蚀速率为1.58 mm/a,其表面腐蚀均匀,有细小凹坑,主要为CO2的腐蚀产物FeCO3以及地层岩屑的主要成分SiO2,此外还夹杂少许地层水中的无机盐,符合CO2冲刷腐蚀特征。建议采用抗CO2腐蚀的管材或向环空添加缓蚀剂的方法预防腐蚀。

To predict the potential risk of corrosion （erosion） in gas drilling beforehand, the online corrosion （erosion） detection device was developed. The device overcomes the weakness of the current technology. Installment of the device on the sand draining pipe-line （or testing pipeline） of gas drilling can conduct a fast and real monitoring of gas drilling corrosion （erosion） rate so as to offer a guide to field implementation of gas drilling and reduce the risk of well control. The field monitoring result shows that the average corro- sion （erosion） rate of the S135 corrosion rod measured by the device is 9. 5 mm/a. The surface is smooth, with local small pits. It is of typical erosion of high speed airflow carrying drilling cuttings. The average corrosion rate of the P110 corrosion rod is 1.58 mrn/a with an even corrosion surface and small pits. The corrosion products are mainly FeCO3 , the corrosion product caused by CO2, and SiO2, the main component of formation cuttings. In addition a small amount of inorganic salt of formation water is included, which is in agree- ment with the erosion and corrosion characteristic of CO2. It is suggested that the CO2 corrosion-resistance pipe should be adopted or corrosion inhibitor should be added to annulus in order to prevent corrosion.