目的 研究渤海某油田L80油管腐蚀机理,对分析该油田油管腐蚀特点、确定油管腐蚀类型、证实井底腐蚀环境、评估油管腐蚀程度和推荐油管防腐材质具有重要意义.方法 基于L80油管宏观腐蚀形貌观察做出的初步判断,首先进行材质分析,其次进行微观腐蚀形貌分析,然后进行腐蚀产物分析,再进行腐蚀程度分析,最后进行电化学试验.结果 该L80油管理化性能及金相组织符合标准,其内外壁腐蚀行为不一致,外壁以均匀腐蚀为主且腐蚀轻微,内壁有一定程度局部腐蚀且腐蚀较严重.腐蚀产物主要含有Fe、S、O和C元素,主要成分为Fe1-xSx、FeCO3和Fe2O3.其外壁点蚀坑深度在15～50 μm之间,内壁点蚀坑深度在80～150 μm之间,内壁微裂纹宽度在20～70 μm之间.CO2分压、H2S分压、含水率和温度对L80油管腐蚀行为有重要影响.结论 该油田井底CO2和H2S共存,L80油管发生了CO2/H2S共存的电化学腐蚀,但点蚀、应力腐蚀开裂(SCC)整体上比较轻微,且L80油管表现出良好的抗硫化物应力开裂(SSC)能力.根据研究结果,推荐现场可以继续使用L80油管.
The work aims to study corrosion mechanism of L80 tubing in an Bohai oilfield,which is of important significance to analyze corrosion features of tubing,determine corrosion type,confirm corrosion environment of downhole,assess corrosion extent and recommend anti-corrosion materials.Based on preliminary estimate of macro corriosion morphology of L80 tubing,material analysis was carried out first,then micro-corrosion morphology was analysed.Thirdly,the corrosion product and corrosion extent were analyzed.Finally,electrochemical test was conducted.Physical and chemical properties as well as metallographic structure of L80 tubing were qualified.Corrosion behavior of inner and outer wall was inconsistent,the corrosion behavior of outer wall was uniform and slight while that of inner wall was localized and serious.The corrosion product mainly contained Fe,S,O and C elements,the main ingredients were Fe1-xSx,FeCO3 and Fe2O3.The pitting depth ofouter wall was 15～50 μm while that of inner wall was 80～150 μm,and crack width of inner wall was 80～150 prm.Partial pressure of CO2 and H2S,temperature and water content had vital impacts on the corrosion behavior of L80 tubing.Pitting corrosion and stress corrosion cracking (SCC) of L80 tubing were relatively slight.CO2 and H2S coexist in the downhole of Bohai oilfield,L80 tubing is subject to CO2/H2S electrochemical corrosion,but the pitting corrosion and stress corrosion cracking (SCC) are relatively slight as a whole and L80 tubing exhibits good SSC capacity.According to the study results,L80 tubing is recommended to be used in offshore oilfield.
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