GeoChemFoam: Direct modelling of multiphase reactive transport in real pore geometries with equilibrium reactions

TL;DR

GeoChemFoam is a novel numerical tool that enables detailed pore-scale simulations of multiphase reactive transport in complex geometries, integrating geochemical reactions with advanced fluid flow modeling.

Contribution

The paper introduces GeoChemFoam, a new multiphase reactive transport solver that combines CFD and geochemical modeling for realistic pore geometries, validated against analytical solutions.

Findings

Pore-scale simulations can improve upscaled models' accuracy.

The model successfully simulates reactive transport in micro-CT images.

Validation confirms the model's reliability.

Abstract

We present the novel numerical model GeoChemFoam, a multiphase reactive transport solver for simulations on complex pore geometries, including microfluidic devices and micro-CT images. 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 our OpenFOAM-based Computational Fluid Dynamics toolbox, and the reaction step solved using Phreeqc, the US geological survey's geochemical solver. The model is validated by comparison with analytical solutions in 1D and 2D geometries. We then applied the model to 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.