Analysing spatial scaling effects in mineral reaction rates in porous media with a hybrid numerical model

Funding: Swiss National Science Foundation; 01.08.2018 – 14.10.2022

Researcher: Po-Wei Huang; PI: Anozie Ebigbo

Project partners: Bernd Flemisch (Universtiy of Stuttgart), Chao-Zhong Qin (Chongqing University, China)

The challenge addressed in this project is the fact that surface-specific reaction rates (including mineral dissolution and precipitation) as a result of flow and transport in porous media cannot be arbitrarily upscaled from the micro- to the macroscale (i.e. pore to Darcy scale). The upscaling is necessary because, while numerical models at the pore scale are accurate, they are computationally expensive and often infeasible for the description of laboratory-scale observations. The approach suggested in the research plan was the use of a hybrid model which spatially couples pore- and Darcy-scale models. The idea was to use a pore-scale model in those parts of the model domain where it is necessary to guarantee accuracy and a macroscale model throughout the rest of the domain.

During the course of the project, we decided to deviate from this approach and attempt an upscaling of the problem — despite the odds — using a bundle-of-tubes model. We decided that the new approach offered a more direct path to linking the two scales than a hybrid model. We focused on the dissolution process, though the approach can be extended to precipitation. See Publication 1 below for more details.

In addition to the upscaling research work, we conducted realistic reactive-transport modelling at the pore scale. To achieve this, we coupled a transport model written within FEniCS with the chemical simulator Reaktoro. This numerical model has been made publicly available by Po-Wei Huang as RetroPy. Within the project, RetroPy was used to investigate a special class of reactive-transport problems: reaction-driven flow. In particular, we studied the importance of the Nernst–Planck model to account for electromigration effects between charged species in aqueous environments. See Publication 2 below for more details. The figure below is an example of simulation results obtained during the project.

Simulation of CO2 dissolution in LiOH brine
Simulation of CO2 dissolution in LiOH brine in a Hele-Shaw cell

Project publications:

  1. Po-Wei Huang, Bernd Flemisch, Chao-Zhong Qin, Martin O. Saar, and Anozie Ebigbo (2022) Relating Darcy-Scale Chemical Reaction Order to Pore-Scale Spatial Heterogeneity. Transport In Porous Media, 144, 507–543.
  2. Po-Wei Huang, Bernd Flemisch, Chao-Zhong Qin, Martin O. Saar, and Anozie Ebigbo (2023) Validating the Nernst–Planck transport model under reaction-driven flow conditions using RetroPy v1.0, Geoscientific Model Development, 16, 4767–4791.

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Letzte Änderung: 12. September 2023