Abstract
GeoChemFoam is an open-source OpenFOAM-based toolbox that includes a range of additional packages that solve various flow processes from multiphase transport with interface transfer, to single-phase flow in multiscale porous media, to reactive transport with mineral dissolution. In this paper, we present a novel multiphase reactive transport solver for simulations on complex pore geometries, including microfluidic devices and micro-CT images, and its implementation in GeoChemFoam. The geochemical model includes bulk and surface equilibrium reactions. Multiphase flow is solved using the Volume-Of-Fluid method, and the transport of species is solved using the continuous species transfer method. The reactive transport equations are solved using a sequential operator splitting method, with the transport step solved using GeoChemFoam, and the reaction step solved using Phreeqc, the US geological survey’s geochemical software. The model and its implementation are validated by comparison with analytical solutions in 1D and 2D geometries. We then simulate multiphase reactive transport in two test pore geometries: a 3D pore cavity and a 3D micro-CT image of Bentheimer sandstone. In each case, we show the pore-scale simulation results can be used to develop upscaled models that are significantly more accurate than standard macro-scale equilibrium models.
Highlights
Reactive transport in porous media is an essential field of study with broad ranging applications in a range of industries including oil and gas production, carbon dioxide (CO2 ) and hydrogen (H2 ) storage, geothermal energy production, nuclear waste disposal, and subsurface contaminant transport (Steefel et al 2005)
One of the objectives of this paper is to demonstrate that an accurate modelling of interface boundary conditions, such as carried out in the continuous species transport (CST) method, is necessary for robust modelling of multiphase reactive transport, because without such modelling artificial mass transfer may arise that can critically damage the chemical equilibrium
We presented a novel multiphase reactive transport model to perform direct numerical simulation of multiphase flow, multicomponent transport and geochemical reactions on pore space images
Summary
Reactive transport in porous media is an essential field of study with broad ranging applications in a range of industries including oil and gas production, carbon dioxide (CO2 ) and hydrogen (H2 ) storage, geothermal energy production, nuclear waste disposal, and subsurface contaminant transport (Steefel et al 2005). Haroun et al (2010) introduced the singlefield approach to model species transport in multiphase systems with interfacial conditions Their method is based on the Volume-Of-Fluid (VOF) method (Hirt and Nichols 1981), where the interface between the two fluids is captured using an indicator function, which is a phase volume fraction. Marschall et al (2012) developed Haroun’s single-field approach into a versatile and precise method for multiphase transport during bubbly flow labelled continuous species transport (CST) This method was extended to problems with moving contact lines by Graveleau et al (2017) and later improved by Maes and Soulaine Maes and Soulaine (2018a) with the introduction of interface compression. We present the simulation and upscaling of reactive transport with two model test cases: (1) first, we simulate carbonic acid formation during dissolution of a CO2 gas bubble in a 3D pore cavity, and (2) we introduce the first results of a multiphase reactive transport simulation on a real 3D pore space with injection of a CaCl2 solution into a micro-CT image of Bentheimer sandstone
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