Department of Energy Resources Engineering, Stanford University, Stanford, CA 94305, USA.
Lab Chip. 2018 Dec 4;18(24):3881-3891. doi: 10.1039/c8lc00793d.
Dissolution of carbonate minerals in porous media is important to many instances of subsurface flow, including geological carbon dioxide (CO2) sequestration, karst formation, and crude-oil reservoir stimulation and acidizing. Of particular interest, geological CO2 storage in deep carbonate reservoirs presents a significant long-term opportunity to mitigate atmospheric carbon emissions. The reactivity of carbonate reservoirs, however, may negatively impact storage formation integrity and hence jeopardize sequestered CO2 storage security. In this work, we develop a novel biogenically calcite-functionalized microvisual device to study the fundamental pore-scale reactive transport dynamics in carbonate formations. Importantly, we discover a new microscale mechanism that dictates the overall behavior of the reactive transport phenomenon, where the reaction product, CO2, due to carbonate rock dissolution forms a separate, protective phase that engulfs the carbonate rock grain and reduces further dissolution. The presence of the separate, protective CO2 phase determines overall dissolution patterns in the storage reservoir and leads to formation of preferential leakage paths. We scale these results using nondimensional numbers to demonstrate their influence on industrial CO2 storage security, safety, and capacity.
多孔介质中碳酸盐矿物的溶解对于许多地下流动情况都很重要，包括地质二氧化碳（CO2）封存、喀斯特地貌形成以及原油储层的增产和酸化。特别值得关注的是，在深层碳酸盐储层中进行地质 CO2 封存为缓解大气碳排放提供了一个重大的长期机会。然而，碳酸盐储层的反应性可能会对储存地层的完整性产生负面影响，从而危及封存的 CO2 储存安全性。在这项工作中，我们开发了一种新颖的生物成因方解石功能化微视觉装置，以研究碳酸盐地层中基本的孔隙尺度反应传输动力学。重要的是，我们发现了一个新的微尺度机制，该机制决定了反应传输现象的整体行为，其中由于碳酸盐岩溶解而形成的反应产物 CO2 形成了一个单独的、保护性的相，包裹了碳酸盐岩颗粒，并减少了进一步的溶解。单独的、保护性的 CO2 相的存在决定了储存储层中的整体溶解模式，并导致优先泄漏路径的形成。我们使用无量纲数对这些结果进行了扩展，以证明它们对工业 CO2 储存安全性、安全性和容量的影响。
