某气田井下管柱的失效原因分析及对策  

Failure Causes and Countermeasures of Downhole Pipe String in a Gas Field

作　　者：罗懿 夏明磊 LUO Yi;XIA Ming-lei(CNOOC(Tianjin)Pipeline Engineering Technology Co.,Ltd.,Tianjin 300452,China)

机构地区：[1]中海油(天津)管道工程技术有限公司,天津300452

出　　处：《装备环境工程》2023年第1期90-96,共7页Equipment Environmental Engineering

摘　　要：目的 分析某气田井下管柱失效的根本原因,并提出有效的解决措施,以减少同类事故的再次发生。方法 采用宏观分析、拉伸性能、化学成分分析、金相分析、腐蚀产物分析、水质分析及结垢预测等方法,对可能造成某气田井下管柱腐蚀的原因进行深入分析。结果 失效件的拉伸性能、化学成分及金相显微组织均满足标准要求,排除因材质缺陷引起腐蚀。宏观分析表明,油管外螺纹与接箍内螺纹及镗孔处存在缝隙,且在缝隙处未预涂丝扣螺纹脂,因此在含有大量 Cl?的腐蚀性环境中发生了缝隙腐蚀。此外,由于该地层水易结垢,当 Ca CO3垢及砂样沉积在缝隙处时,再次构成缝隙腐蚀发生的条件,从而加速腐蚀的进行。结论 在下管柱作业中,在接箍与油管旋合处有必要预涂螺纹脂,防止服役环境中的腐蚀介质在缝隙处造成缝隙腐蚀而减少井下管柱的服役寿命。The work aims to analyze the failure cause of downhole pipe string in a gas field, and put forward effective solutions to reduce the recurrence of similar accidents. Through macro analysis, tensile properties, chemical composition analysis,metallographic analysis, corrosion product analysis, water quality analysis and scaling prediction, the possible causes of downhole pipe string corrosion in a gas field were deeply analyzed. The tensile properties, chemical composition and metallographic microstructure of the failed parts met the standard requirements, and the corrosion caused by material defects was excluded. The macro analysis showed that there was a gap between the external thread of the oil pipe and the internal thread of the coupling and the boring, and the screw thread grease was not precoated at the gap, so the gap corrosion occurred in the corrosive environment containing a large amount of Cl?. In addition, because the formation water was easy to scale, when CaCO3scale and sand sample were deposited at the gap, the condition for gap corrosion was constituted again, accelerating the corrosion. It is necessary to precoat thread grease at the screw joint of coupling and oil pipe during operation of downhole pipe string to prevent gap corrosion caused by corrosive medium in service environment and avoid reducing the service life of downhole pipe string.

关 键 词：井下管柱 碳钢 缝隙腐蚀 螺纹脂 接箍 解决措施 

分 类 号：TG172[金属学及工艺—金属表面处理]