The injection of CO₂ deep underground, i.e., geologic carbon sequestration, has attracted considerable attention for climate change mitigation. A reliable caprock for secure containment is essential, alongside strategies for sealing flow paths to prevent leaks. In this study, we explore ways in which reactions of CO₂ with CaSiO₃ can be used for targeted mineral precipitation and permeability control in situ. Previous work has suggested that certain CaSiO₃ polymorphs can produce pore-filling precipitates that successfully inhibit flow, whereas others produce precipitates with little impact. In this work, a one-dimensional reactive transport model was developed for a centimeter-scale system to explore connections between the pore and continuum scale. The model considers four reactions involving CaSiO₃, CaCO₃, SiO_2(am), and the crystalline calcium silicate hydrate (CCSH) tobermorite. A key feature is incorporation of microporosity, with an attempt to represent favorable volume expanding changes from CCSH precipitation in porous media. At 150°C and 1.1 MPa CO₂, representing typical laboratory conditions, the model predicts significant permeability drop when reacting the pseudowollastonite CaSiO₃ polymorph at elevated pH to produce CaCO₃, SiO_2(am), and tobermorite. The effect of increasing pH via by NaOH addition, which increases CO₂ solubility, increases CaSiO₃ dissolution, and supports tobermorite supersaturation. In contrast, reaction of the wollastonite polymorph results in CaCO₃ and SiO_2(am) formation, with limited permeability impact. Wollastonite's lower solubility and slower dissolution rate inhibits tobermorite formation. Simulation at the high pressures representative of deep subsurface field conditions (40°C and 7.5 MPa CO₂) suggests that reaction of CaSiO₃ with CO₂ could reduce permeability and seal unwanted leakage pathways.

中文翻译：

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通过硅酸钙与二氧化碳的反应来密封多孔介质，以增强地质固碳的安全性

在地下深处注入CO ₂，即地质​​固碳，已经为缓解气候变化吸引了相当多的关注。可靠的保护盖是必不可少的，此外，还有用于密封流路以防止泄漏的策略。在这项研究中，我们探索了将CO ₂与CaSiO _3的反应用于目标矿物沉淀和原位渗透率控制的方法。先前的工作表明某些CaSiO ₃多晶型物可产生可成功抑制流动的充填孔的沉淀物，而其他多晶型物产生的影响却很小。在这项工作中，为厘米尺度的系统开发了一个一维反应性传输模型，以探索孔隙和连续尺度之间的联系。该模型考虑了四个反应，分别涉及CaSiO ₃，CaCO ₃，SiO _2（am）和结晶硅酸钙水合物（CCSH）雪铁矿。一个关键特征是微孔的结合，试图代表多孔介质中CCSH沉淀产生的有利的体积膨胀变化。在150°C和1.1 MPa CO _2下代表典型的实验室条件，该模型预测当假硅灰石CaSiO ₃多晶型物在升高的pH下反应生成CaCO ₃，SiO _2（am）和钙蒙脱石_时，渗透率会显着下降。通过添加NaOH来增加pH值的效果，这可以增加CO _2的溶解度，增加CaSiO _3的溶解度，并支持黑钨矿的过饱和。相反，硅灰石多晶型物的反应导致CaCO ₃和SiO _2（am）地层，对渗透性的影响有限。硅灰石的较低溶解度和较慢的溶解速度抑制了硅铁矿的形成。在代表深地下场条件（40°C和7.5 MPa CO ₂）的高压下进行的模拟表明，CaSiO ₃与CO _2的反应可能会降低渗透率并密封不希望的泄漏途径。