A COMSOL–GEMS interface for modeling coupled reactive-transport geochemical processes

Abstract

An interface was developed between COMSOL Multiphysics finite element analysis software and (geo)chemical modeling platform, GEMS, for the reactive-transport modeling of (geo)chemical processes in variably saturated porous media. The two standalone software packages are managed from the interface that uses a non-iterative operator splitting technique to couple the transport (COMSOL) and reaction (GEMS) processes. The interface allows modeling media with complex chemistry (e.g. cement) using GEMS thermodynamic database formats. Benchmark comparisons show that the developed interface can be used to predict a variety of reactive-transport processes accurately. The full functionality of the interface was demonstrated to model transport processes, governed by extended Nernst-Plank equation, in Class H Portland cement samples in high pressure and temperature autoclaves simulating systems that are used to store captured carbon dioxide (CO 2) in geological reservoirs.

A nearly self-sufficient framework for modelling reactive-transport processes in concrete

“…The framework for modelling reactive-transport ionic species in concrete is based on the solution of the mass conservation equation [24][25][26]:…”

“…1 is the sink/source term that accounts for the exchange between the solid and ionic species in the concrete pore solution following reactive processes such as chloride binding and release. The total flux of species, N i , in the concrete pore solution is written as a combination of diffusion, chemical activity, electrical migration, and advection mechanisms [24][25][26]:…”

“…where n s is the number of ionic species. It should be noted that electro-neutrality must be maintained throughout the system; therefore, the charge-balance of the ionic species in the electrolyte is also enforced [25]. The advection term in Eq.…”

“…8 represents a simplified version of moisture flow in concrete that is based on water content alone. Although they are not presented here, moisture transport models that consider the movement of vapour and liquid phases separately can be used for more accurate representation of the problem [25].…”

Computational Efficiency of Decoupling Approach in Solving Reactive Transport Model: A Case Study of Pyrite Oxidative Dissolution

“…For example, Shao et al [27] uses it to couple a dual-permeability model with a soil mechanics model for landslide stability evaluation on a hillslope scale. Azad et al [28] build up an interface between COMSOL and GEMS, a chemical modelling platform, for the reactive transport modelling in variably saturated porous media, while Nardi et al [29] and Jara et al [30] couple two standalone simulation programs, COMSOL and PHREEQC, for the reactive transport modelling.…”