长宁页岩气集气管道内腐蚀穿孔原因探究

Research on Causes of Corrosion Perforation in Changning Shale Gas Gathering Pipelines

页岩气集输系统输送介质复杂,易造成管线内腐蚀穿孔泄漏,严重影响页岩气田正常开发与生产。通过对长宁页岩气田穿孔腐蚀管道及输送介质取样分析,发现气质中CO_(2)摩尔分数为0.44%,水质中检测出高含SRB(硫酸盐还原菌)(1.1×10^(5)个/mL)、Cl^(-)(21913.14 mg/L);采用SEM、XPS、EDS等微观分析仪器分析了集气管内腐蚀产物,其中含有FeCO_(3)(9.31%)、FeS(3.54%)、FeS_(2)(19.09%);得出造成长宁页岩气生产管线腐蚀的主要原因是CO_(2)、SRB细菌以及Cl^(-)的协同腐蚀作用,CO_(2)溶于管壁表面的液膜,产生酸性腐蚀环境,CO_(2)与Fe发生电化学腐蚀反应,形成点蚀坑,并产生Fe^(2+);SRB细菌将水质中的SO^(2-)_(4)转变为H_(2)S,与Fe^(2+)结合生成FeS、FeS_(2),并在Cl^(-)的促进作用下,快速造成管道腐蚀穿孔。

The transmission medium of shale gas gathering and transportation system is complex,which is easy to cause corrosion,perforation and leakage in the pipeline,seriously affecting the normal development and production of shale gas field.Based on the sampling analysis of perforated corrosion pipeline and transportation medium in Changning shale gas field,the results showed that the mole fraction of CO_(2)in the gas quality was 0.44%,and SRB(1.1×10^(5)/mL)and Cl^(-)(21913.14 mg/L)were detected in the water.Using SEM,EDS,XPS and other micro-analysis instruments to analyze the corrosion products in the gas collector,it was found that the corrosion products contained FeCO_(3)(9.31%),FeS(3.54%),and FeS^(2)(19.09%).Results showed that the main cause of the corrosion of the Changning shale gas production pipeline was the synergistic corrosion of CO_(2),SRB bacteria and Cl^(-).CO_(2)dissolved in the liquid film on the surface of the pipe wall,resulting in an acidic corrosion environment,and electrochemical corrosion of CO_(2)and Fe occurred.Pitting pits were formed and Fe^(2+)was produced.SRB bacteria transformed SO^(2-)_(4)in water quality into H_(2)S,combining with Fe^(2+)to generate FeS and FeS_(2),and under the promotion of Cl^(-),quickly leading to corrosion perforation of pipelines.