Relating Darcy-Scale Chemical Reaction Order to Pore-Scale Spatial Heterogeneity
Publication date
2022-09-01
Document type
Research article
Author
Organisational unit
Scopus ID
Pubmed ID
Series or journal
Transport in Porous Media
Periodical volume
144
First page
507
Last page
543
Peer-reviewed
✅
Part of the university bibliography
✅
Keyword
Mineral dissolution
Reaction rate law
Reactive transport
Upscaling
Abstract
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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