Advances in porous media science and engineering from InterPore2020 perspective

    Natural, artificial, and biological porous media can be seen everywhere in our daily lives. Transport phenomena in porous media, such as flow, diffusion, reaction, adsorption and deformation, are encountered in a wide variety of practical applications and scientific interests over widely disparate length scales, from molecular, to pore, core, and field scales. However, determination of transport properties in porous media remains a challenging issue. During the 12th Annual Meeting of the International Society for Porous Media (InterPore), held online from August 31-September 4, 2020, advances on porous media science and engineering in very broad areas were presented. The meeting was attended by more than 750 participants from across the globe, and a significant milestone was achieved in the history of InterPore conferences due to its online interactive platform. Participants could access the pre-recorded talks, leave comments and questions, chat with each other, one week before the conference. Then, all the feedback related to a talk was discussed in the presence of the author during several Q&A sessions. Invited and Keynote talks were live, and were also recorded. Each Q&A session was moderated by two experts, who first reviewed the 8 contributions of their session and then summarized the questions for each talk. The author could further elaborate their work and answer the questions.Cited as: Cai, J., Hajibeygi, H., Yao, J., Hassanizadeh, S.M. Advances in porous media science and engineering from InterPore2020 perspective. Advances in Geo-Energy Research, 2020, 4(4): 352-355, doi: 10.46690/ager.2020.04.0

Two sides of a coin: a critical review, and mathematical and phenomenological study of what we call hydromechanical coupling

In this paper a brief and critical review of the current literature on hydro-mechanical coupling is presented. Furthermore, anenhanced discrete element model is used to investigate the mutual relationship of soil water retention curve and suction stress curves and how the two are affected as a result of change in the initial porosity of the soil sample. The model revealed the suction stress values in wetting were less affected as in drying branch as a result of the change in the initial porosity of the soil sample

Modeling the dynamics of partial wetting

The behavior of interfaces and contact lines arises from intermolecular interactions like Van der Waals forces. To consider this multi–phase behavior on the continuum scale, appropriate physical descriptions must be formulated. While the Continuum Surface Force model is well–engineered for the description of interfaces, there is still a lack of treatment of contact lines, which are represented by the intersection of a fluid–fluid interface and a solid boundary surface. In our approach we use the “non compensated Young force” to model contact line dynamics and therefore use an extension to the Navier–Stokes equations in analogy to the extension of a two–phase interface in the CSF model. Because particle–based descriptions are well–suited for changing and moving interfaces we use Smoothed Particle Hydrodynamics. In this way we are not only able to calculate the equilibrium state of a two–phase interface with a static contact angle, but also for instance able to simulate droplet shapes and their dynamical evolution with corresponding contact angles towards the equilibrium state, as well as different pore wetting behavior. Together with the capability to model density differences, this approach has a high potential to model recent challenges of two–phase transport in porous media. Especially with respect to moving contact lines this is a novelty and indispensable for problems, where the dynamic contact angle dominates the system behavior

Modeling the Transport and Retention of Nanoparticles in a Single Partially Saturated Pore in Soil

Pore-network models are powerful tools for studying particle transport in complex porous media, and investigating the role of interfaces in their fate. The first step in simulating particle transport using pore-network models is to quantitatively describe particle transport in a single pore, and obtain relationships between pore-averaged deposition rate coefficients and various pore-scale parameters. So, in this study, a three-dimensional (3D) mathematical model is developed to simulate the transport and retention of nanoparticles within a single partially saturated pore with an angular cross-section. The model accounts for particle deposition at solid-water interfaces (SWIs), air-water interfaces (AWIs), and air-water-solid (AWS) contact regions. We provide a novel formulation for particle diffusive transport from AWI to AWS, where particles are assumed to be retained irreversibly by capillary forces. The model involves 12 dimensionless parameters representing various physicochemical conditions. The 3D model results are averaged over the pore cross-section and then fitted to breakthrough curves from one-dimensional (1D) advection-dispersion-sorption equations with three-site kinetics to estimate 1D-averaged deposition rate coefficients at interfaces. We find that half-corner angle, particle size, radius of curvature of AWI, and mean flow velocity have a significant effect on those coefficients. In contrast, chemical parameters such as ionic strength and surface potentials of particles and interfaces have negligible effects. AWS is found to be the major retention site for particles, especially for hydrophobic particles. We develop algebraic relationships between 1D-averaged deposition rate coefficients at interfaces vis-à-vis various pore-scale parameters. These relationships are needed for pore-network models to upscale nanoparticle transport to continuum scale

Experimental determination of in-plane permeability of nonwoven thin fibrous materials

Knowledge of hydraulic properties is crucial for understanding and modeling fluid flow in thin porous media. In this work, we have developed a new simple custom-built apparatus to measure the intrinsic permeability of a single thin fibrous sheet in the in-plane direction. The permeability was measured for two types of nonwoven thin fibrous porous materials using either the water or gas phase. For each layer, the measurements have been done for different combinations of flow direction and fiber orientation. The permeability values measured using gas and water were approximately close to each other. The permeability of the two samples was found to be anisotropic and the principal permeabilities were determined based on the measurements

Experimental Evaluation of Fluid Connectivity in Two-Phase Flow in Porous Media During Drainage

This study aims to experimentally investigate the possibility of combining two extended continuum theories for two-phase flow. One of these theories considers interfacial area as a separate state variable, and the other explicitly discriminates between connected and disconnected phases. This combination enhances our potential to effectively model the apparent hysteresis, which generally dominates two-phase flow. Using optical microscopy, we perform microfluidic experiments in quasi-2D artificial porous media for various cyclic displacement processes and boundary conditions. Specifically for a number of sequential drainage processes, with detailed image (post-)processing, pore-scale parameters such as the interfacial area between the phases (wetting, non-wetting, and solid), and local capillary pressure, as well as macroscopic parameters like saturation, are estimated. We show that discriminating between connected and disconnected clusters and the concept of the interfacial area as a separate state variable can be an appropriate way of modeling hysteresis in a two-phase flow scheme. The drainage datasets of capillary pressure, saturation, and specific interfacial area, are plotted as a surface, given by f (Pc, sw, awn) = 0. These surfaces accommodate all data points within a reasonable experimental error, irrespective of the boundary conditions, as long as the corresponding liquid is connected to its inlet. However, this concept also shows signs of reduced efficiency as a modeling approach in datasets gathered through combining experiments with higher volumetric fluxes. We attribute this observation to the effect of the porous medium geometry on the phase distribution. This yields further elaboration, in which this speculation is thoroughly studied and analyzed

Improved pressure decay method for measuring CO2-water diffusion coefficient without convection interference

Carbon dioxide (CO2) storage in deep aquifers is a promising solution to mitigate anthropogenic CO2 emissions. CO2 solubility in brine results in a non-buoyant phase providing an effective trapping mechanism. However, experimental work and numerical simulation results have shown that this diffusion-driven mechanism is a relatively slow process. Accurate determination of CO2 diffusion coefficient is, therefore, essential. The pressure decay method is a widely employed technique for measuring diffusion coefficients of gases in bulk liquids or porous media. It involves introducing a volume of gas on top of the liquid in a closed system and monitoring the pressure decay over time. While the method is generally simple and accurate, artifacts from natural convection can significantly influence the measured diffusion for liquids that exhibit an increase in density due to gas dissolution. This work presents an improved experimental approach for measuring CO2 diffusion coefficients in water in a convection-fee system. Our setup consisted of single open-ended borosilicate capillary tubes filled with water inside a high-pressure vessel filled with CO2 gas. The water-filled capillary tubes were placed with their open ends facing down. This configuration exhibits bottom-top diffusion leading to gravity-stable CO2 diffusion in water free of gravity-induced convection and viscous fingering. The effects of pressure and salinity variations confirm the agreement between our results and values reported in the literature. We also performed additional analysis to determine the effective diffusion coefficient of CO2 in a porous medium. The proposed technique can be used to measure the diffusion coefficients for other gas-liquid systems

Experimental Analysis of Mass Exchange Across a Heterogeneity Interface: Role of Counter-Current Transport and Non-Linear Diffusion

Solute transport in heterogeneous and fractured systems is a complex process given the permeability contrasts and the time scales discrepancies of transport in high-permeability versus low-permeability regions. We studied this phenomenon by injecting a solute (dyed water) in a micromodel comprising a single channel in contact with a porous medium and evaluated the mass exchange across the interface between the channel and porous medium (resembling the interface between free flow and porous media regions). Two sets of transport experiments were performed at three injection rates of 0.01, 0.1, and 1 ml/hr. Injection of dyed water into a clean-water-filled micromodel (referred to as the loading process hereafter) and injection of clean water into a dyed-water-filled micromodel (referred to as the unloading process hereafter). The dynamics of solute transport was recorded using time-lapse optical imaging. Our experimental results demonstrated the change of the mass exchange rate coefficient with time and a much smaller transfer rate coefficient during the unloading compared to the loading process. It is proposed that concentration-dependent counter-current advection-diffusion cause slow-down and further delay in the transport. These results may provide further explanation for the observed slow release of contamination in aquifers