页岩气气田集输系统腐蚀控制技术研究与应用

目的针对页岩气气田集输系统面临的腐蚀问题,采用系统分析及模拟评价手段,进行不同阶段的腐蚀行为及规律研究,明确腐蚀主要原因及应对措施。 方法系统分析了各阶段的腐蚀主控因素,根据腐蚀特征将页岩气开发分为一个排采阶段及两个生产阶段,采用失重模拟实验、扫描电镜、能谱、XRD等手段研究了不同阶段的腐蚀行为及规律。 结果在5~18 m/s流速条件下,砂含量及流态变化较大的地方的腐蚀以冲蚀为主,电化学腐蚀为辅,且冲蚀表现为犁削型冲蚀损伤；随着流速降低,砂沉积及返排液沉积腐蚀特征发生转变,明确了SRB和CO₂共存条件是导致集气管线穿孔失效的主要原因；通过模拟SRB成膜的现场工况,获得了点蚀速率为5.86 mm/a,这与部分管线穿孔失效的点蚀速率相当。 结论提出切实可行的腐蚀控制方案,主要包括使用耐冲蚀材料、增大壁厚、加注杀菌缓蚀剂,并应用于页岩气现场,使集输系统失效降低90%以上。 

Research and application of corrosion control technology in gathering and transportation system of shale gas field

ObjectiveIn view of the serious corrosion problems faced to the gathering and transportation system of shale gas fields, systematic analysis and simulation evaluation were used to study the corrosion behavior and laws at different stages to clarify the main reasons for corrosion and countermeasures. MethodsThe main corrosion factors were systematically analyzed for the serious corrosion problems of gathering and transportation system in shale gas field, and according to the corrosion characteristics of the system,the shale gas development was divided into one drainage gas recovery stage and two stages of production, and the corrosion behavior and laws of different stages were studied by weight loss, SEM, EDS, XRD and other methods. ResultsThe corrosion is dominant in the places where the sand content and fluid state change greatly, it was appeared as plough-type damage, and supplemented by electrochemical corrosion under the condition of flow velocity of 5-18 m/s. As the flow rate decreased ,the corrosion characteristics was changed by deposition of sand and flowback fluid, which makes it clear that the coexistence of SRB and carbon dioxide is the main reason for the perforation failure of gas gathering pipeline. The on-site working conditions of SRB film formation were simulated, a pitting corrosion rate of 5.86 mm/a, it was equivalent to the part of the failure pipeline. ConclusionsA feasible and practical corrosion control scheme was proposed, mainly including using erosion-resistant materials, increasing wall thickness, adding sterilization and corrosion inhibitors, and applying them to the shale gas field to reduce the failure of the gathering and transportation system by more than 90%.