Journal
TRANSPORT IN POROUS MEDIA
Volume 144, Issue 2, Pages 507-543Publisher
SPRINGER
DOI: 10.1007/s11242-022-01817-0
Keywords
Reactive transport; Mineral dissolution; Upscaling; Reaction rate law
Categories
Funding
- Swiss Federal Institute of Technology Zurich
- Swiss National Science Foundation [175673]
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Spatial scaling effects lead to discrepancies in mineral dissolution rates measured at different scales. In this study, we investigate the impact of pore-scale spatial heterogeneity in porous media on overall mineral dissolution rates, and propose a constitutive relation based on Darcy-scale reaction order to model reactive transport at the Darcy scale. Our results suggest that mineral spatial heterogeneity can be inferred from solute concentration measurements in flow-through dissolution experiments.
Due to spatial scaling effects, there is a discrepancy in mineral dissolution rates measured at different spatial scales. Many reasons for this spatial scaling effect can be given. We investigate one such reason, i.e., how pore-scale spatial heterogeneity in porous media affects overall mineral dissolution rates. Using the bundle-of-tubes model as an analogy for porous media, we show that the Darcy-scale reaction order increases as the statistical similarity between the pore sizes and the effective-surface-area ratio of the porous sample decreases. The analytical results quantify mineral spatial heterogeneity using the Darcy-scale reaction order and give a mechanistic explanation to the usage of reaction order in Darcy-scale modeling. The relation is used as a constitutive relation of reactive transport at the Darcy scale. We test the constitutive relation by simulating flow-through experiments. The proposed constitutive relation is able to model the solute breakthrough curve of the simulations. Our results imply that we can infer mineral spatial heterogeneity of a porous media using measured solute concentration over time in a flow-through dissolution experiment.
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