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Recoupling flow and chemistry in variably saturated reactive transport modelling - An algorithm to accurately couple the feedback of chemistry on water consumption, variable porosity and flow

Abstract : Most reactive transport codes and algorithms decouple the flow from the reactive transport calculations. In some cases, geochemical reactions lead to significant modifications of porosity or water-content, which can have an impact on the flow. The flow problem is based on the continuity equation and is described in terms of pressure. However, most reactive transport codes do not model the pressure-evolution through mineral reactions. The aim of this study is to recouple the reactive transport and the flow, by providing an accurate description of the evolution of both the porosity and the water in the reactive system. We discuss a formulation of the geochemical solver, based on a mole-conservation, which allows an accurate computation of the volume and masses of all phases. This allows for a water and pore volume computation at the scale of the REV which can impact the fluid-pressure, hence the flow. Additionally, solving the geochemical equilibrium in terms of moles instead of concentrations is more accurate for problems involving important mineral reactions. Finally, this method is suited to saturated, unsaturated and two-phase flow. This method is easy to implement and can be used in different reactive transport simulators, regardless of their numerical approaches. We also test the numerical efficiency of this approach and apply it to fully-coupled problems involving variable porosity, variable saturation, water production/consumption.
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https://hal-mines-paristech.archives-ouvertes.fr/hal-01909167
Contributor : Vincent Lagneau <>
Submitted on : Tuesday, October 30, 2018 - 9:42:06 PM
Last modification on : Thursday, November 12, 2020 - 3:18:02 PM

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Nicolas Seigneur, J. Corvisier, A. Dauzères, Vincent Lagneau. Recoupling flow and chemistry in variably saturated reactive transport modelling - An algorithm to accurately couple the feedback of chemistry on water consumption, variable porosity and flow. Advances in Water Resources, Elsevier, 2018, 122, pp.355-366. ⟨10.1016/j.advwatres.2018.10.025⟩. ⟨hal-01909167⟩

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