| 摘要: |
| 目的 明确某含硫天然气集输管线连续穿孔失效原因。方法 按照建立的失效分析流程，采用宏观形貌分析、理化性能检测、金相组织分析、微观腐蚀形貌和腐蚀产物成分分析等方法，结合管线服役历史、运行工况环境情况，结合智能检测与模拟实验，对失效原因及过程进行了分析。结果 管材的理化性能、金相组织均满足标准、设计要求；管线两次失效均发生在局部地势低洼点，呈现出腐蚀坑尺寸沿腐蚀发展方向减小的特征，失效形式表现为局部腐蚀穿孔失效；腐蚀产物结构疏松，主要为铁的硫化物和氧化物；智能内检测结果显示管道全线普遍存在不同程度的金属损失缺陷，且缺陷在管道底部、低洼处存在集中分布；模拟实验表明，未加注缓蚀剂时，管材腐蚀速率达到0.3056mm/a；PIPESIM计算结果显示，失效时失效点处气、液相流速均处在较低水平。结论 单井站脱水装置脱水不彻底，在未加注缓蚀剂的情况下，管线内部积液发生严重点腐蚀，点蚀坑内发生自催化酸化，使腐蚀加剧，最终发生穿孔。 |
| 关键词: 集输管线 失效分析 硫化氢 底部腐蚀 自催化酸化 |
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| Analysis of Failure Causes for Continuous Perforation in a Sulfur-Bearing Natural Gas Gathering and Transportation Pipeline |
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zhongyang1,2, wangyongbo3,2, molin1,2, tangyongfan1,2, jiangzhi4,2, liufujun5,2
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1.Research Institute of Natural Gas Technology, PetroChina Southwest Oil&2.Gasfield Company;3.PetroChina Southwest Oil&4.Central Sichuan Oil and Gas Mine, PetroChina Southwest Oil&5.Chongqing Gas District, PetroChina Southwest Oil &
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| Abstract: |
| Objective In this paper, we elucidate the root cause of continuous perforation in a sulfur-bearing natural gas gathering and transportation pipeline. Methods In accordance with the established failure analysis procedure, a comprehensive approach was employed, encompassing macroscopic morphology analysis, physicochemical property testing, metallographic structure examination, microscopic corrosion morphology assessment, and corrosion product composition analysis. By integrating the pipeline's service history, operational conditions, environmental factors, as well as results from intelligent detection and simulation experiments, an in-depth analysis of the causes and mechanisms of the failure was conducted. Results The physicochemical mechanical and microstructure of the pipeline comply with the standards and design requirements. Both two times of pipeline failures occurred at locally low-lying points, exhibiting a characteristic pattern where the size of the corrosion pits diminished in the direction of corrosion propagation. The failure mode was characterized by localized corrosion leading to perforation. The corrosion products were structurally loose, primarily comprising iron sulfides and oxides. The findings from the intelligent internal inspection revealed that metal loss defects of varying degrees were present throughout the pipeline, with a concentration at the bottom and low-lying areas. Simulation experiments indicated that in the absence of corrosion inhibitors, the corrosion rate of the pipe material reached 0.3056 mm/year. According to PIPESIM calculations, upon pipeline failure, both gas and liquid phase flow velocities at the failure point were at relatively low levels. Conclusion The accumulation of liquid in the pipeline lead to severe pitting corrosion. Autocatalytic acidification within the pits further exacerbates the corrosion process, ultimately resulting in perforation failure. The dehydration process at the single well station was inadequate, resulting in incomplete removal of water. The absence of corrosion inhibitors allowed accumulated liquid within the pipeline to cause severe pitting corrosion. Furthermore, self-catalyzed acidification within these pits exacerbated the corrosion, ultimately leading to pipe perforation. |
| Key words: gathering and transportation pipeline failure analysis H2S bottom corrosion autocatalytic acidification |
