A2井表层套管腐蚀机理分析与防护对策

Analysis of Corrosion Mechanism of Surface Casing of A2 Well and Protection Methods

目的通过对A2井表层套管外腐蚀产物组分化验与电化学测试,确认其腐蚀原因,并结合现场实际情况制定防护措施。方法对收集到的腐蚀产物进行能谱元素、XRD组分分析,并参考NACE-TM0194—2014和SY/T 0532—2012进行SRB、TGB分析。结果能谱分析显示,腐蚀产物主要由氧、铁、碳元素组成,其次还含有少量钠、钾、氯、硫元素;XRD分析显示,腐蚀产物主要成分为Ba SO4、Fe2O3和FeS;细菌化验显示,腐蚀产物中含有SRB和TGB,具备通过微生物代谢提供H2S的条件。实际检测A2井涂敷防腐实施后,表面腐蚀得到明显控制。结论 A2井表层套管外腐蚀产物主要为Fe2O3和FeS,腐蚀的主要原因为大气环境氧腐蚀,次要原因是细菌作用产生的次生硫化氢腐蚀,产物中大量的重晶石和少量的无机盐来源于钻井液,海水为细菌提供了来源。基于腐蚀产物分析结果,采取的主要防护措施是隔绝大气和水。通过对石油管道涂敷技术调研分析,结合A2井作业空间,提供了一种STOPAQ防腐膏挤注与涂敷防护方案。该技术操作安全方便,无需对腐蚀面进行特殊预处理,作业过程中无需停产。

The work aims to analyze and confirm the corrosion causes by component test and electrochemical test of external corrosion products in the surface casing of A2 well and prepare the anti-corrosion measures according to the analysis result and the actual situation of the site.Energy spectrum element analysis and XRD component analysis were carried out on the collected corrosion product,and SRB and TGB analysis were also performed with reference to NACE-TM0194-2014 and SY/T 0532-2012.From the energy spectrum analysis,corrosion products mainly consisted of O,Fe and C elements,as well as a small amount of Na,K,Cl and S elements.XRD analysis showed that the main components of corrosion products were BaSO4,Fe2O3 and FeS.Bacteriologic examination revealed that the corrosion products contained SRB and TGB,which provided the conditions for H2S through microbial metabolism.The external corrosion products of the surface casing of A2 well are mainly Fe2O3 and FeS.The main cause of corrosion is oxygen corrosion,and minor cause is secondary sulfide corrosion generated by bacterial action.A large amount of barite and a small amount of inorganic salts in the product are from drilling fluid,and seawater provides a source of bacterial.Based on the results of corrosion product analysis,the main anti-corrosion measure is to isolate the air and water from the surface casing.Based on the research and analysis of oil pipeline coating technology and combined with the survey of A2 well operation space,a kind of STOPAQ anti-corrosion plaster and coating protection scheme is provided.The scheme is safe and convenient to operate without special precondition on erosional surface and no decommission.The surface erosion has been obviously controlled by the actual testing of corrosion resistance measures for surface casing of the A2 well.