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Dissolution pattern formation during acid-rock interaction exerts a strong control on permeability evolution in carbonate reservoirs, with important implications for geological CO2 storage and subsurface flow. Yet predictive capability remains limited, as existing transport-reaction scaling models often fail to accurately reproduce experimental observations of dissolution patterns. This study aims to develop a framework for more accurate interpretation of dissolution behaviours by considering the coupled evolution of fluid reactivity and reaction-front propagation. We conduct a series of core-scale flow-through experiments on samples from two limestones with distinct structural heterogeneity, injected with CO2-rich water at flow rates spanning over three orders of magnitude. Effluent chemistry is continuously monitored and combined with high-resolution X-ray imaging, enabling direct visualization of the development of dissolution patterns and the migration of reaction fronts within these experiments. We also compile similar experimental data from the literature to discuss the generality of our observations further. The results show systematic transitions from compact or inlet-localized dissolution to increasingly extended wormhole structures as flow rates increase, with fluid reactivity sustained further along the flow path. We observe that dissolution regimes are uniquely correlated with how long a fluid can sustain reactivity but not with the inlet pH or classical Péclet-Damköhler values calculated at the initial injection conditions. The observed trend persists across both lithologies despite their differing heterogeneity and is consistent with patterns identified through reanalysis of published dissolution experiments using a variety of reactive fluids and porous media. These results highlight reactivity persistence as a physically grounded and transferable framework for interpreting and predicting carbonate dissolution patterns in heterogeneous porous media, although defining quantitative regime boundaries requires further analysis.
| References | Vafaie, A., Soler, J. M., Cama, J., Kivi, I. R., & Vilarrasa, V. (2024). A 3D Darcy-scale reactive transport modeling of experimental wormhole formation in limestone under geological CO2 storage conditions. Vafaie, A., Cama, J., Soler, J. M., Grgic, D., & Vilarrasa, V. (2023). Chemo-hydro-mechanical effects of CO2 injection into a permeable limestone. International journal of coal geology, 278, 104359. Menke, H. P., Andrew, M. G., Blunt, M. J., & Bijeljic, B. J. C. G. (2016). Reservoir condition imaging of reactive transport in heterogeneous carbonates using fast synchrotron tomography—Effect of initial pore structure and flow conditions. Chemical Geology, 428, 15-26. |
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| Country | United Kingdom |
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