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A 2.5D Reactive Transport Model for Fracture Alteration Simulation
journal contribution
posted on 2016-06-30, 00:00 authored by Hang Deng, Sergi Molins, Carl Steefel, Donald DePaolo, Marco Voltolini, Li Yang, Jonathan Ajo-FranklinUnderstanding fracture alteration
resulting from geochemical reactions
is critical in predicting fluid migration in the subsurface and is
relevant to multiple environmental challenges. Here, we present a
novel 2.5D continuum reactive transport model that captures and predicts
the spatial pattern of fracture aperture change and the development
of an altered layer in the near-fracture region. The model considers
permeability heterogeneity in the fracture plane and updates fracture
apertures and flow fields based on local reactions. It tracks the
reaction front of each mineral phase and calculates the thickness
of the altered layer. Given this treatment, the model is able to account
for the diffusion limitation on reaction rates associated with the
altered layer. The model results are in good agreement with an experimental
study in which a CO2-acidified brine was injected into
a fracture in the Duperow Dolomite, causing dissolution of calcite
and dolomite that result in the formation of a preferential flow channel
and an altered layer. With an effective diffusion coefficient consistent
with the experimentally observed porosity of the altered layer, the
model captures the progressive decrease in the dissolution rate of
the fast-reacting mineral in the altered layer.
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Keywords
reaction frontCO 2geochemical reactionspermeability heterogeneitydissolution ratefluid migrationflow channeldiffusion limitationfracture aperture change2.5 D Reactive Transport Modelreaction ratesFracture Alteration Simulationfracture planeDuperow Dolomiteflow fieldsnovel 2.5 D continuum reactive transport modelmineral phaseupdates fracture aperturesmodel resultsdiffusion coefficientfracture alteration
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