Speaker
Description
pH-induced reactive transport among miscible phases in porous environments is pivotal in carbon capture and storage (CCS) applications, especially in the carbon sequestration process, where the mixing process among the miscible phases affects the pH transport. However, separating the pH migration from the mixing is challenging due to the pore-scale heterogeneities and limited understanding of the role of pH in the mixing and displacement processes within porous media. In this study, we designed two parallel experiments. In both experiments, we displaced weak acidic water-glycerol solution with basic water solution in porous media. The mixing experiment used Rhodamine 6G as a conservative tracer to visualize the mixing and displacement process, which allowed us to derive a theoretical pH pattern based solely on the mixing degree. The second experiment employed pH-sensitive fluorescent dye Pyranine to directly visualize the actual pH migration pattern (Figure 1). Both processes were captured using confocal microscopy for detailed visualization and analysis. By comparing these two patterns, we could identify the special behavior of pH transport during the miscible displacement. Our experimental results reveal that pH propagation consistently precedes the mixing and displacement processes. Specifically, by comparing the pore volumes (PV) required to reach the 95% displaced breakthrough points, we observed that the actual pH pattern arrives earlier than the predicted pH pattern derived from the mixing process. These findings suggest that modeling complex subsurface processes in both natural and industrial applications, particularly in scenarios where pH-dependent reactions play a dominant role in mass transfer and fluid displacement, has to consider the high diffusion rate of pH.
| Country | Israel |
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