Transient increase in reactive surface and the macroscopic Damköhler number in chalk dissolution

Y. Yang*, M. Rogowska, Y. Zheng, Stefan Bruns, C. Gundlach, S.L.S. Stipp, H. O. Sørensen

*Corresponding author for this work

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Abstract

Surface area is an important input parameter for reactive transport modelling and it changes with time when rocks dissolve. Here we show direct observations of increased surface area due to chalk (predominantly CaCO3) dissolution, using 3D in situ X-ray microtomography. This transient increase cannot be explained by changes in fluid accessibility or by surface roughening that arises from preferential leaching. We use model simulations to explain how this increase in surface area correlates with the size of the Damköhler space, defined macroscopically using a phenomenological dissolution rate law and the cumulative surface of the microstructure. We attribute this transient increase to the coupling between fluid flow and mineral dissolution and argue that the extent is determined by the advective penetration distance of the reactants. We conclude that using a macroscopic dimensionless number as a qualitative indicator for microstructure evolution has limited applicability.
Original languageEnglish
JournalJournal of Hydrology
Volume571
Pages (from-to)21-35
Number of pages15
ISSN0022-1694
DOIs
Publication statusPublished - 2019

Keywords

  • X-ray tomography
  • In situ imaging
  • Chalk Dissolution
  • Microstructure evolution
  • Reactive surface area
  • Damköhler number

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