Transport In Porous Media Research Articles

Data-Driven Closure Parametrizations with Metrics: Dispersive Transport

This work presents a data-driven framework for multi-scale parametrization of velocity-dependent dispersive transport in porous media. Pore-scale flow and transport simulations are conducted on periodic pore geometries, and volume averaging is used to isolate dispersive transport, producing parameters for the dispersive closure term at the representative elementary volume scale. After validation on unit cells with symmetric and asymmetric geometries, a convolutional neural network is trained to predict dispersivity directly from pore geometry images. Descriptive metrics are also introduced to better understand the parameter space and are used to build a neural network that predicts dispersivity based solely on these metrics. While the models predict longitudinal dispersivity well, transversal dispersivity remains difficult to capture, likely requiring more advanced models to fully describe pore-scale transversal dynamics.

Solute transport due to periodic loading in a soft porous material

In soft porous media, deformation drives solute transport via the intrinsic coupling between flow of the fluid and rearrangement of the pore structure. Solute transport driven by periodic loading, in particular, can be of great relevance in applications including the geomechanics of contaminants in the subsurface and the biomechanics of nutrient transport in living tissues and scaffolds for tissue engineering. However, the basic features of this process have not previously been systematically investigated. Here, we fill this hole in the context of a one-dimensional model problem. We do so by expanding the results from a companion study, in which we explored the poromechanics of periodic deformations, by introducing and analysing the impact of the resulting fluid and solid motion on solute transport. We first characterise the independent roles of the three main mechanisms of solute transport in porous media – advection, molecular diffusion and hydrodynamic dispersion – by examining their impacts on the solute concentration profile during one loading cycle. We next explore the impact of the transport parameters, showing how these alter the relative importance of diffusion and dispersion. We then explore the loading parameters by considering a range of loading periods – from slow to fast, relative to the poroelastic time scale – and amplitudes – from infinitesimal to large. We show that solute spreading over several loading cycles increases monotonically with amplitude, but is maximised for intermediate periods because of the increasing poromechanical localisation of the flow and deformation near the permeable boundary as the period decreases.

Nanoparticles Transport in Porous Media During EOR Operations: A Wide-Ranging Review of Mechanisms, Mathematical Models, Influencing Parameters, Challenges, and Prospects

Nanoparticles Transport in Porous Media During EOR Operations: A Wide-Ranging Review of Mechanisms, Mathematical Models, Influencing Parameters, Challenges, and Prospects

A Model of the Degrading Solute Transport in Porous Media based on the Multi-Stage Kinetic Equation

A mathematical model of solute transport in porous media with two adsorption zones was developed, incorporating balance and kinetic equations, and initial and boundary conditions. The model was enhanced to account for multistage deposition kinetics in both adsorption zones, and numerical methods were employed to solve the problem. An algorithm using the finite difference method was presented as a solution. Computer experiments were conducted to ascertain the effect of different parameters of the model on solute transport, and the results of the study were analyzed. The primary focus of this study is to assess the impact of parameters within the kinetic equations on the transport process. These parameters are crucial in determining the intensity of adsorption during various stages of the process. The findings of this study demonstrate that multistage deposition kinetics significantly influences both the transport and adsorption processes. Furthermore, the presence of two distinct intensity areas in the concentration profile of the adsorbed substance is observed. This phenomenon is attributed to the effects of multistage kinetics.

Gas transport in saturated porous media at pore scale: Numerical simulations and hypergravity experiments

Gas transport in porous media has been widely investigated in the geo-environmental, geotechnical, and chemical engineering fields. However, the mechanism for the transition of the gas flow pattern under the influence of the gravity field is not clear. This study gives some insights into this issue by using a hypergravity microfluidic experiment and pore-scale simulations based on the phase-field method. As the centrifugal acceleration increases, the gas transport pattern undergoes a gradual transition from a continuous finger flow to a discontinuous bubbly flow. An increase in pore size results in a weakening of the capillary effect, allowing the buoyancy force to gradually become the dominant force. The numerical simulation method reproduces experimental results of hypergravity microfluidics for chips with different pore sizes. Enhanced buoyancy effect leads to a significant reduction in sweep efficiency. Hypergravity field enhances separation of gas and liquid phases, thereby facilitating the generation of discontinuous bubbles. The dividing line between continuous and discontinuous flow is defined based on dimensionless numbers, which are supplemented by the numerical simulation results.

Capillary-driven liquid transport in a multistage micropillar array

Liquid transport in porous media is governed by capillary pressure and permeability, which are influenced by pore size regionally. Additionally, there exists a trade-off between achieving high capillary pressure and maintaining high permeability. In this work, porous structures consisting of micropillar arrays of gradient pore sizes are designed to balance such a regional trade-off to enable enhanced capillary-driven liquid transport. A dimensionless analytical model describing the wicking dynamics is developed to optimize the pore distribution. The model determines the optimal pore configuration characterized by a negative structural gradient, which minimizes the global wicking time for a given length of the porous media. The optimization result shows that the liquid wicking time can be reduced by up to 25% in the gradient structure compared to a uniform structure of the same length. Experimental validation of the optimized configuration is performed by measuring the wicking dynamics of different liquids in the porous structures. The results show that two-stage and three-stage gradient structures reduce the wicking time by 13.4% and 18.1%, respectively, which agrees well with theoretical predictions. Furthermore, we demonstrate a pillar spacing of 200 μm with the optimal capillary performance parameter K/reff of 4.6 μm at a given side length–spacing ratio of 1.27. The proposed model provides a practical tool for designing and optimizing porous structures at the pore scale to achieve maximum capillary flow rates.

A theoretical model to predict the influence of physicochemical conditions on colloid transport, attachment, detachment, and blocking in porous media

A theoretical model to predict the influence of physicochemical conditions on colloid transport, attachment, detachment, and blocking in porous media

Effects of Pore‐Scale Three‐Dimensional Flow and Fluid Inertia on Mineral Dissolution

AbstractMineral dissolution releases ions into fluids and alters pore structures, affecting geochemistry and subsurface fluid flow. Thus, mineral dissolution plays a crucial role in many subsurface processes and applications. Pore‐scale fluid flow often controls mineral dissolution by controlling concentration gradients at fluid‐solid interfaces. In particular, recent studies have shown that fluid inertia can significantly affect reactive transport in porous and fractured media by inducing unique flow structures such as recirculating flows. However, the effects of pore‐scale flow and fluid inertia on mineral dissolution remain largely unknown. To address this knowledge gap, we combined visual laboratory experiments and micro‐continuum pore‐scale reactive transport modeling to investigate the effects of pore‐scale flow and fluid inertia on mineral dissolution dynamics. Through flow topology analysis, we identified unique patterns of 2D and 3D recirculating flows and their distinctive effects on dissolution. The simulation results revealed that 3D flow topology and fluid inertia dramatically alter the spatiotemporal dynamics of mineral dissolution. Furthermore, we found that the 3D flow topology fundamentally changes the upscaled relationship between porosity and reactive surface area compared to a conventional relationship, which is commonly used in continuum‐scale modeling. These findings highlight the critical role of 3D flow and fluid inertia in modeling mineral dissolution across scales, from the pore scale to the Darcy scale.

Visualization investigation of fluid transport in multiscale porous media for CO2-EOR based on microfluidic technology.

During oil extraction, the recovery rates of traditional methods have been gradually declining. CO2-enhanced oil recovery (CO2-EOR) has been utilized since the 1960s; however, in recent years, it has garnered renewed attention due to its environmental benefits and economic advantages. However, there are few reports addressing multiphase mass transfer in micro- and nano-scale pores. This study employs microfluidic technology to simulate the pore structures of real reservoir rocks. A fracture-matrix porous medium chip with a network channel structure and a microscale porous medium chip featuring multiple pore-throat ratios were designed to investigate the effects of cross-scale interactions, network channel geometries, and the Jamin effect on fluid flow patterns and oil recovery rates during both CO2 miscible and CO2 immiscible flooding processes. The experiments demonstrated that the cross-scale effect facilitates the rapid achievement of a 100% recovery rate during CO2 miscible flooding, but exacerbates gas channeling during CO2 immiscible flooding, resulting in a decreased recovery rate. The Jamin effect becomes more pronounced with increasing pore-throat ratios, and the substantial capillary resistance generated by this effect in regions with high pore-throat ratios significantly reduces the rate of increase in recovery during CO2 miscible flooding, as well as the overall recovery rate during CO2 immiscible flooding. This study enhances the understanding of multiphase mass transfer in reservoir conditions and provides critical insights for optimizing CO2-EOR strategies, ultimately contributing to more efficient oil recovery and supporting sustainable practices in the energy sector.

A Temporally Relaxed Theory of Nonequilibrium Solute Transport in Porous Media With Spatial Dispersivity Involving Flexible Boundary

A Temporally Relaxed Theory of Nonequilibrium Solute Transport in Porous Media With Spatial Dispersivity Involving Flexible Boundary

Unveiling the Impact of Microfractures on Longitudinal Dispersion Coefficients in Porous Media

Longitudinal dispersion coefficient is a key parameter governing solute transport in porous media, with significant implications for various industrial processes. However, the impact of microfractures on the longitudinal dispersion coefficient remains insufficiently understood. In this study, pore-scale direct numerical simulations are performed to analyze solute transport in microfractured porous media during unstable miscible displacement. Spatiotemporal concentration profiles were fitted to the analytical solution of the convection–dispersion equation to quantify the longitudinal dispersion coefficient across different microfracture configurations. The results indicate that the longitudinal dispersion coefficient is highly sensitive to microfracture characteristics. Specifically, an increased projection length of microfractures in the flow direction and a reduced lateral projection length enhance longitudinal dispersion at the outlet. When Peclet number ≥1, the longitudinal dispersion coefficient follows a three-stage variation pattern along the flow direction, with microfracture connectivity and orientation dominating its scale sensitivity. Furthermore, both diffusion-dominated and mixed advective-diffusion regimes are observed. In diffusion-dominated regimes, significant channeling alters the applicability of traditional scaling laws, with the relationship between longitudinal dispersion coefficient and porosity holding only when the Peclet number is below 0.07. These results provide a comprehensive scale-up framework for CO2 miscible flooding in unconventional reservoirs and CO2 storage in saline aquifers, offering valuable insights for the numerical modeling of heterogeneous reservoir development.

Relevance of Local Dispersion on Mixing Enhancement in Engineering Injection and Extraction Systems in Porous Media: Insights from Laboratory Bench-Scale Experiments and Modeling

This work investigates the dynamics of flow, transport and mixing in subsurface porous media during an engineered injection–extraction (EIE) system. We perform laboratory bench-scale experiments mimicking an EIE system in an unconfined aquifer, and we explore the role of local dispersion on mixing enhancement. The experimental setup is equipped with four wells operated in a sequence, one at a time, creating transient flows and a fluctuating water table impacting the transport dynamics of an injected dye tracer plume. A high-resolution imaging technique is applied to monitor the spatial and temporal evolution of the plume concentration. The experiments are performed in porous media with fine and coarse grain sizes and considering two different sequences of injection and extraction. The plume spreading and mixing are quantified by computing the spatial moments and the plume area, respectively. The Okubo–Weiss parameter is calculated over the plume area to correlate mixing enhancement with changes in flow topology. The results indicate that the operation of EIE system significantly enhances mixing and spreading, particularly when the effective Okubo–Weiss parameter is higher. Furthermore, the mixing enhancement is larger in the experiments performed in the coarse porous media, indicating the importance of local dispersion as a factor for mixing enhancement in EIE systems.

Interaction of λ-cyhalothrin with chitosan and quartz sand: Attachment, transport, and cotransport in porous media

Interaction of λ-cyhalothrin with chitosan and quartz sand: Attachment, transport, and cotransport in porous media

The transport of polystyrene microplastics in saturated porous media: Impacts of functional groups and solution chemistry.

The transport of polystyrene microplastics in saturated porous media: Impacts of functional groups and solution chemistry.

Prediction of both diffusive and hydraulic conductance in the pore network model extracted from 3D images using deep learning

Abstract Pore network modeling (PNM) with network extracted from 3D images is widely used for studying mass transport in porous media, with its accuracy heavily dependent on the precise determination of hydraulic and diffusive conductance values of local pore pairs. Deep learning (DL) prediction based on true pore geometry offers a promising approach for conductance estimation. However, due to arbitrarily orientation and the lack of explicit inlet and outlet surfaces in 3D extracted pore pair geometries, existing studies [24,25] have relied only on 2D cross section images for hydraulic conductance prediction. A custom finite difference method was recently developed, capable exclusively of estimating diffusion conductance from 3D pore geometry [26]. In this work, a convolutional neural network (CNN) was trained to estimate both diffusive and hydraulic conductance values, with reference ground truth values obtained by applying the Lattice Boltzmann Method (LBM) on 3D pore pair geometries. The predicted pore pair conductance values from the CNN closely matched the LBM results on unseen segmented image data. This study highlights the importance of using the full 3D pore pair geometry for accurate hydraulic conductance evaluation, rather than relying solely on 2D throat cross sections. To evaluate the generality of our method, we calculated the permeability and diffusivity of 3D porous media across a wide range of porosities using PNM with local conductance values predicted by our DL model. Comparisons with results of LBM indicate that while diffusivity was accurately predicted, permeability was underestimated. This underestimation is attributed to the over-segmentation of pore spaces, which resulted in an underestimated flow rate.

Interception History Drives Colloid Transport Variance in Porous Media.

Colloid transport in porous media is traditionally predicted using the principle of constant fractional removal for each grain passed, such that concentrations decrease exponentially with transport distance. This approach successfully describes transport when repulsive barriers to attachment are absent. However, repulsive barriers characterize environmental contexts wherein attachment upon grain interception is inhibited, causing colloid concentrations to decay nonexponentially with distance from the source and thwarting prediction. The pervasiveness of these nonexponential trends across wide-ranging experiments suggests that a fundamental process is at play. Here, we propose a paradigm shift by considering constant fractional loss with each interception rather than with each grain passed. We show that by recognizing the history of grain interceptions, a pathway is revealed toward a simple and predictive framework in which nonexponential trends emerge. This shift in perspective offers the possibility of colloid transport prediction in settings that were previously infeasible using classic filtration theory, with potential applications in contexts ranging from environmental (e.g., groundwater aquifer protection) to biomedical (e.g., drug delivery).

Global sensitivity analysis of mass transfer and reaction dynamics for electrokinetic transport in porous media

Global sensitivity analysis of mass transfer and reaction dynamics for electrokinetic transport in porous media

Unraveling two-dimensional modeling of multispecies reactive transport in porous media with variable dispersivity

Unraveling two-dimensional modeling of multispecies reactive transport in porous media with variable dispersivity

Representative elementary volume (REV) and flow-dependent solute transport in homogenous porous media

Representative elementary volume (REV) and flow-dependent solute transport in homogenous porous media

Influence of iron-modified biochar on phosphate transport and deposition in saturated porous media under varying pH, ionic strength, and biochar dosage.

Influence of iron-modified biochar on phosphate transport and deposition in saturated porous media under varying pH, ionic strength, and biochar dosage.