Ca^(2+)对3Cr钢在CO_(2)环境中腐蚀行为的影响

Effect of Ca^(2+)on the Corrosion Behavior of 3Cr Steel in CO_(2)Environment

随着油气开发进入到高含水期,高Ca^(2+)、高Cl-的地层水环境对管柱的安全服役提出了更高的要求。采用高温高压釜模拟井下流态环境,结合电化学研究结果,分析了Ca^(2+)浓度和暴露时间对3Cr钢腐蚀行为的影响。结果表明:尽管Ca^(2+)的存在会促使溶液酸化,但3Cr钢在含Ca^(2+)溶液中的腐蚀速率更多取决于试样表面的膜层质量。当溶液中总Cl-浓度为128000 mg/L,Ca^(2+)浓度在0~3600 mg/L的范围内时,3Cr钢在Ca^(2+)浓度为1080 mg/L时平均失重速率最大,为2.2 mm/a。在Ca^(2+)含量为180 mg/L的环境中,3Cr钢的失重速率曲线显示3Cr钢的失重速率随时间呈反“V”变化趋势,当腐蚀时间为240 h时,试样的平均失重速率达到最大值。当将3Cr钢放入通入CO_(2)的含有Ca^(2+)的溶液中时,3Cr钢表面形成Fe_(x)Ca_(1-x)CO_(3)化合物,Fe/Ca之间并无严格的比例,产物形态取决于溶液中的Ca^(2+)含量。

As the development of oil and gas enters a high water cut stage,the formation water environment with high Ca^(2+)and Cl⁃poses higher requirements for the safe service of pipe columns.In this work,the influence of Ca^(2+)concentration and exposure time on the corrosion behavior of 3Cr steel was analyzed by using high temperature autoclave to simulate the downhole flow environment and combining with the electrochemi⁃cal research results.Research results showed that although the presence of Ca^(2+)could promote solution acidification,the corrosion rate of 3Cr steel in solutions containing Ca^(2+)depended more on the quality of the film on the sample surface.When the total Cl-concentration in the solu⁃tion was 128000 mg/L and the Ca^(2+)concentration ranged from 0 to 3600 mg/L,the maximum average weight loss rate of 2.2 mm/a occurred at the Ca^(2+)concentration of 1080 mg/L.Meanwhile,in an environment with a Ca^(2+)concentration of 180 mg/L,the weight loss rate curve of 3Cr steel showed an inverse“V”trend of weight loss rate over time,and the average weight loss rate of the sample reached the maximum value at the corrosion time of 240 h.When 3Cr steel was immersed in a solution containing Ca^(2+)with introducing CO_(2),the Fe_(x)Ca_(1-x)CO_(3)compounds were formed on the surface of 3Cr steel.In addition,there was no strict ratio between Fe/Ca,and the product states depended on the Ca^(2+)con⁃centration in the solution.