CO_(2)地质封存与利用环境下水泥单矿C_(2)S的腐蚀速率

Study on Corrosion Rate of Cement Monomineralic C_(2)S in CO_(2)Geological Sequestration Environment

在CO_(2)地质封存和利用过程中,固井水泥容易与井下的酸性介质CO_(2)发生碳酸化反应,腐蚀固井水泥石造成水泥石力学性能大幅度衰退。针对水泥石单矿C_(2)S在CO_(2)地质封存和利用环境中腐蚀反应速率不清晰的问题,通过SEM、XRD以及TG的测试方法,定量分析C_(2)S腐蚀产物的变化规律。根据腐蚀产物CaCO_(3)的摩尔生成率和非稳态扩散渗透模型拟合得到腐蚀反应产物CaCO_(3)的生成系数α。SEM实验结果表明,腐蚀反应后C_(2)S水泥单矿颗粒的表面均有较大改变,生成了部分腐蚀产物CaCO_(3);XRD结果表明,单矿C_(2)S腐蚀产物CaCO_(3)的晶型主要有方解石和文石;TG测试结果表明,C_(2)S水泥单矿随着腐蚀龄期的增加,腐蚀产物的量均明显增加。拟合结果表明,C_(2)S腐蚀产物生成速率随着温度的升高而增大,90℃下CaCO_(3)腐蚀产物的生成速率系数α最大为54.90。

In geological sequestration and application of CO_(2),the cement used in well cementing is easy to react with CO_(2),an acidic gas produced downhole,causing the set cement for well cementing to be corroded and the mechanical properties of the set cement decline remarkably.Presently,the corrosion rate of the set cement monomineralic C_(2)S in CO_(2)geological sequestration and application environment is still not clearly understood.In this study,several measuring methods,such as SEM,XRD and TG etc.,are used to quantitatively analyze the changes of the corrosion products of C_(2)S.The yield coefficientαof the corrosion product CaCO_(3)can be obtained by fitting the molar yield rate of the corrosion product CaCO_(3)with the non-steady state diffusion permeation model.The SEM experimental results show that after the corrosion reaction,the surfaces of the C_(2)S cement monomineralic particles have undergone great changes,producing part of the corrosion product CaCO_(3);The XRD experimental results show that crystal forms of the corrosion product CaCO_(3)of the monomineralic C_(2)S are mainly calcite and aragonite.The TG experimental results show that the amount of the corrosion products increases with the corrosion time of the C_(2)S cement monomineral.The fitting results indicate that the yield rate of the corrosion products of C_(2)S increases with temperature,at 90℃the yield rate of the corrosion product CaCO_(3)has a maximum yield coefficientαof 54.90.