Multiscale modelling of transport in clays from the molecular to the sample scale

Abstract

Multiscale modelling of transport in clays from the molecular to the sample scale. Comptes Rendus Géoscience, AbstractWe report some recent applications of multiscale modelling to the transport of ions, water and CO 2 in clays. On the one hand, simulations on different scales allow to investigate the physico-chemical processes underlying the geochemical and transport behaviour of these fluids in the interparticle pores and at the surface of clay minerals. We discuss more specifically the insights gained from molecular simulations on the acidity of surface edge sites, ion exchange and the behaviour of clay interlayers in contact with a CO 2 reservoir. On the other hand, upscaling the descriptions from the molecular level to the macroscopic scale without forgetting the fundamental role of interfaces on the mesoscopic scale provides a means to capture complex phenomena such as electrokinetic couplings. We illustrate the complementarity of molecular dynamics, lattice-based mesoscopic simulations and Pore Network Models to address this issue.

Ionic Transport in Nano-Porous Clays with Consideration of Electrostatic Effects

“…21). Upscaling strategies have been developed to derive macroscopic diffusion parameters from microscopic information (Rotenberg et al 2007a(Rotenberg et al ,b, 2014Jardat et al 2009;Bourg and Sposito 2010;Churakov and Gimmi 2011;Churakov et al 2014) and these can be complemented by RT modeling that takes into account the complexity of the chemical reactivity of the material in fi ner details (e.g., adsorption processes, activity coeffi cients) However, it is noteworthy that the interpretation of diffusion data is complicated by complex microstructures that are dependent on physical and chemical conditions, and that these microstructures have not been yet characterized down to the scale of the smallest pores, i.e., the interlayer pores. The connectivity of the pore network connectivity across the full range of pore sizes has not been successfully determined for any of the investigated systems as well.…”

Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies

“…Quantum mechanics (QM) techniques have been used to study clay-cation and clay-cation-water interactions (Chatterjee et al, 1999;Sposito et al, 1999;Ren et al, 2012;Tribe et al, 2012). A recent multiscale approach including ab initio molecular dynamics (MD), classical MD and mesoscopic simulations emphasized the challenge in describing the phenomena with different length and time scales in clay studies (Rotenberg et al, 2014). The benefits of using molecular modelling are evident because the understanding of the chemical reactions requires that the description of the electron structure of the system and the dependence of the thermodynamics as a function of time are known.…”

A fractional differential scheme for the effective transport properties of multiscale reactive porous media: Applications to clayey geomaterials

“…However, Archie's relationship is no longer valid for geomaterials such as clay materials containing nanopores of only a few nanometers in length that are filled with an electrolyte possessing special transport properties. These particular transport properties, existing at nanopore scale, result from complex surface physico‐chemical phenomena occurring at the liquid‐mineral interface; these include chemical reactions at mineral surface sites, electrostatic interactions between the surface and ions, wettings, and electrokinetic couplings 55–57 . All these surface physico‐chemical phenomena often refer to surface conduction 12,30,32,58 or surface diffusion 59–60 .…”