Mid-term thesis Nassim Cheikh

In this work we introduce a new pore-scale model for investigating particulate transport and  retention in porous media. This model is able to capture particle-particle interactions that has a big impact on the particulate motion in dense suspensions. Particles including mineral grain, iron oxides, microplastics and bacteria are ubiquitous in subsurface flow. These elements have numerous applications, for example,
the injection of nanoirons is foreseen to remediate contaminated groundwater. The aim of our work is to simulate the impact of particle transport on the properties of the porous medium. Our model relies on a
Euler-Euler approach that describes the suspension as two inter-penetrated continua — one for the carrier fluid and one for the solid particles — that exchange momentum through interphase coupling.
Unlike Euler-Lagrange approach that resolves all particle-particle and particle-wall interactions, including collisions, rolling, sliding, and others, Euler-Euler approach uses constitutive models. For example, non-Newtonian viscosity models represent these interactions and the overall mechanical behavior of the suspension (plastic, elastic, viscoelastic). We have implemented the rheology model proposed by for dense suspension. It consists in an effective shear viscosity and a normal particle pressure. The model accounts for the particles and the suspension compressibility. Using this framework, we investigate how permeability-porosity relationships evolve during particle transport in
dilute suspensions. We show that the agreement with CFD-DEM simulations is good, depending on the drag force model used. We then study the mechanical behavior of dense suspensions subject to compressive forces.
We highlight the important role played by solid pressure—that is, normal stresses—in reaching the compressibility limit. We subsequently focus on particle retention in a single pore and in a complex porous medium. In particular, we demonstrate that rheology plays a predominant role in clog formation, as do parameters such as the particle-to-throat diameter ratio W/D and particle concentration. The study also highlights several forms of particle trapping during particle transport. When the W/D ratio
is approximately equal to 3.5, a form of clogging typical of deep filtration beds—also known as straining—is observed. When the W/D ratio is less than 2, a filter cake forms at the entrance to the porous medium. The insights provided by this pore-scale model improve our understanding of physical clogging mechanisms and can guide subsurface engineering applications, including the mitigation of permeability decline near wellbores and the design of more effective remediation strategies for contaminants trapped by capillary forces within the pore space.