泡排剂对页岩气集气管道内壁腐蚀行为的影响研究

Study on the Corrosion Behavior of Shale Gas Gathering Pipeline Inner Wall Affected by Foam Drainage Agent

摘要: 页岩气井生产中后期普遍面临井筒及集气管道积液问题，泡沫排水采气工艺是保障气井稳产的关键技术手段，但工艺所加注的泡排剂会改变管道内部腐蚀环境，对管线钢的腐蚀规律产生显著影响。为揭示现场常用泡排剂对集气管道内壁腐蚀的作用机制，以页岩气田集气管线采用L360NS管线钢为研究对象，利用电化学测试，系统研究了在0.3%加注浓度下起泡剂、消泡剂及其复配体系与空白实验对管线钢均匀腐蚀与局部点蚀行为的影响规律。结果表明：单加0.3%起泡剂会显著负移腐蚀电位、增大腐蚀电流密度、降低界面电荷转移电阻，强烈促进均匀腐蚀与点蚀萌生；单加0.3%消泡剂可正向偏移腐蚀电位、减小腐蚀电流密度、形成致密防护膜，表现出优良的缓蚀与抗点蚀性能；起泡剂与消泡剂复配后，消泡剂可有效抵消起泡剂的腐蚀加剧效应，使腐蚀速率与局部腐蚀风险回落至接近空白组水平。该研究结果可为页岩气田泡排剂加注方案优化、集气管道腐蚀防控与安全运行提供实验依据与理论支撑。

Abstract: Liquid loading in wellbores and gathering pipelines commonly occurs during the middle and late production stages of shale gas wells. Foam drainage gas recovery technology serves as a key method to ensure stable gas production. However, the injected foam drainage agents alter the internal corrosive environment of pipelines and significantly affect the corrosion characteristics of pipeline steel. To clarify the action mechanism of commonly used foam drainage agents on the corrosion of the inner wall of gathering pipelines, L360NS pipeline steel applied in shale gas field gathering pipelines was selected as the research material. Electrochemical tests were conducted to systematically investigate the uniform corrosion and localized pitting corrosion of the steel exposed to foaming agent, defoamer, and their composite system at a mass concentration of 0.3%, with a blank group set for comparison. The results show that the single addition of 0.3% foaming agent remarkably shifts the corrosion potential negatively, increases corrosion current density, and reduces the interfacial charge transfer resistance, which greatly accelerates uniform corrosion and pitting initiation. The single addition of 0.3% defoamer moves the corrosion potential positively, lowers corrosion current density, and forms a dense protective film, presenting excellent corrosion inhibition and pitting resistance. When the foaming agent is compounded with the defoamer, the defoamer can effectively offset the corrosion acceleration effect of the foaming agent, bringing the corrosion rate and localized corrosion risk close to those of the blank group. The findings provide experimental basis and theoretical support for the optimization of foam drainage agent injection schemes, corrosion prevention and control, as well as safe operation of gathering pipelines in shale gas fields.