To better understand the geochemical alteration of the interface between wellbore Portland cement and rock because of potential leakage during CO₂ storage operations, we performed percolation experiments using three solid cores each made of two half-cylinders, one of hydrated Portland cement and the other of calcareous rock (limestone, marl or sandstone). These experiments were run under atmospheric (P_CO2 = 10^−3.4 bar and room temperature) and supercritical (P_CO2 = 130 bar and 60 °C) CO₂ conditions with an injection pH of 6.4 and 3.2, respectively. The variation in the aqueous chemistry of the outflows was reproduced by 2D reactive transport simulations.

The experimental and model results showed that under atmospheric conditions, a slight dissolution of portlandite and C-S-H near the cement-channel interface was responsible for an incipient alteration of cement that was prevented by the precipitation of brucite. By contrast, under supercritical conditions, cement alteration was marked owing to an intense dissolution of cementitious phases (portlandite, ettringite, Si-hydrogarnet and hydrotalcite), causing an increase in porosity.

Overall, the results show that potential CO₂ leakage during and after CO₂ injection will cause an alteration of the hydrated Portland cement, resulting in a loss of its sealing properties. The alteration of low-porosity calcareous rocks, such as the ones used in this study, is only expected to be minor.

为了更好地了解由于CO ₂储存操作过程中潜在的泄漏而导致的井筒波特兰水泥与岩石之间界面的地球化学变化，我们使用三个实心岩心进行渗滤实验，每个实心岩心由两个半圆柱体组成，其中一个是水合波特兰水泥，另一个是水化波特兰水泥。钙质岩（石灰岩，泥灰岩或砂岩）。这些实验在大气（P _CO2 = 10 ^-3.4 bar和室温）和超临界（P _CO2 = 130 bar和60°C）CO ₂条件下进行，注入pH分别为6.4和3.2。流出物的水化学变化通过2D反应输运模拟再现。

实验和模型结果表明，在大气条件下，水泥通道界面附近的波特兰石和CSH的少量溶解是造成初期水泥蚀变的原因，水镁石的沉淀阻止了这种变化。相比之下，在超临界条件下，由于胶凝相（硅酸钙石，钙矾石，硅氢石榴石和水滑石）的强烈溶解而引起水泥蚀变，从而导致孔隙度增加。

总体而言，结果表明，在注入CO _2的过程中和注入CO ₂之后，潜在的CO ₂泄漏将引起水合硅酸盐水泥的改变，从而导致其密封性能的损失。低孔隙度的钙质岩石，如本研究中所用的岩石，仅被认为是微小的。