Carbon dioxide geosequestration in deep saline aquifers or oil and gas reservoirs is a key technology to mitigate anthropogenic greenhouse gas emissions. Porous carbonate rock is a potential host rock for CO₂ storage; however, carbonate rock chemically reacts when exposed to the acidic brine (which is created by the addition of CO₂, CO₂-saturated brine). These reactive transport processes are only poorly understood, particularly at the micrometre scale, and importantly how this affects the geomechanical rock properties. We thus imaged a heterogeneous oolitic limestone (Savonnières limestone) core before and after flooding with brine and CO₂-saturated brine at representative reservoir conditions (323 K temperature, 10 MPa pore pressure, 5 MPa effective stress) in-situ at high resolutions (3.43 μm and 1.25 μm voxel size) in 3D with an x-ray micro-computed tomograph; and measured the changes in nano-scale mechanical properties induced by acid exposure. Indeed the carbonate rock matrix partially dissolved, and absolute and effective porosity and permeability significantly increased. This dissolution was confined to the original flow channels and inlet points. Importantly, the rock matrix weakened significantly (- 47% in indentation modulus) due to the acid exposure.

在深层盐水层或油气储层中进行二氧化碳地质隔离是减轻人为温室气体排放的一项关键技术。碳酸盐多孔岩是潜在的CO ₂储集岩。然而，碳酸盐岩石在暴露于酸性盐水（由添加CO ₂，CO ₂饱和盐水产生）后会发生化学反应。人们对这些反应性运输过程的了解甚少，尤其是在微米级别，而且重要的是，这如何影响岩土力学特性。因此，我们对盐水和CO ₂注入前后的非均质橄榄岩灰岩（Savonnières石灰岩）岩心进行了成像。-在具有代表性的储层条件下（323 K温度，10 MPa孔隙压力，5 MPa有效应力）在3D高分辨率下（X射线微计算机断层扫描仪）以高分辨率（3.43μm和1.25μm体素尺寸）就地饱和盐水；并测量了酸暴露引起的纳米级机械性能的变化。实际上，碳酸盐岩基质部分溶解，并且绝对有效孔隙率和渗透率显着提高。这种溶解仅限于原始流动通道和入口点。重要的是，由于暴露于酸中，岩石基体显着减弱（压痕模量约为47％）。