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| Titel |
Mixing-induced dissolution in fingering reactive flow |
| VerfasserIn |
Juan J. Hidalgo, Yoar Cabeza, Marco Dentz, Jesús Carrera |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088360
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| Publikation (Nr.) |
 EGU/EGU2014-2458.pdf |
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| Zusammenfassung |
| The evolution of porosity in carbonate reservoirs during CO2 injection, and the wormhole
formation in karst aquifers can be attributed to fast equilibrium reactions, which are
characterized by large Damköhler numbers. Under these conditions the reaction
rate is mixing-controlled, and can be quantified in terms of the mixing rate of the
conservative components of the chemical system [De Simoniet al. (2005), Water. Resour.
Res.].
Here, we study the calcite dissolution during the convective-driven mixing of CO2 in a
carbonate saline aquifer. The CO2-brine mixture is denser than the two initial fluids, leading
to a Rayleigh-Bénard-type instability known as convective mixing, which greatly accelerates
CO2 dissolution. The dissolution front can display a stable or fingering shape depending on
the relation of the governing forces.
We explore the feedback between fluid instabilites, porosity evolution, and permeability
changes by means of numerical simulations of a CO2 stationary layer dissolving into brine
using an analogue-fluid system with a non-monotonic density-concentration curve
[Neufeld et al. (2010), Geophys. Res. Lett.; Backhaus, et al. (2011), Phys. Rev. Lett.;
Hidalgoet al. (2013), Adv. Water Resour.]. We derive an analytical expresion for the
speciation contribution to the reaction rate which is valid under a wide range of
reservoir conditions (pH< 8.3). This allows us to analyze systematically the impact of
conservative mixing mechanisms on the dynamics of the complex reactive flow
system.
Our findings show how the developed porosity patterns depend on the fingering
instabilities caused by the convective-driven dissolution of the CO2, the movement
of the receding CO2-brine interface, and the properties of the chemical system. |
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