Transport Behavior In Porous Media Research Articles

Study on advection–dispersion behavior for simulation of 3H, 99Tc, and 90Sr transport in crushed sandstone of column experiments

Abstract In order to establish a universal and safety-compliant post-closure safety assessment technique, it is necessary to develop appropriate models to explain the migration behavior of radioactive materials within the rock system. Advection-dispersion experiments (ADE) have proven successful in designing transport models through a calibration/validation process of breakthrough curves (BTCs). In the present investigation, we employed a dynamic column device to examine the transport of Tritium (3H), Technetium-99 (99Tc), and Strontium-90 (90Sr) in crushed sandstone. Non-reactive transport experiments utilizing conservative tracers enabled us to determine the transport parameters, including retardation factors (R) and dispersivity (α). Our study focused on investigating the surface complexation model (SCM) using an additive approach coupled with the advection-dispersion equation to simulate the reactive transport behavior of 90Sr. The results affirm the robustness of our chosen thermodynamic database and modeling approach, emphasizing the criticality of accurately modeling and predicting reactive transport behavior in porous media.

Molecular simulations of hydrogen diffusion in underground porous media: Implications for storage under varying pressure, confinement, and surface chemistry conditions

Assessing the feasibility of porous formations for hydrogen geo-storage demands a comprehensive understanding of hydrogen (H2) transport behavior in porous media at subsurface conditions. In this study, we employ molecular dynamics simulations to evaluate the effects of pressure (20–500 atm), pore size (2–20 nm), and surface composition on H2 diffusion and interactions within organic and inorganic slit pores. Our analysis of H2 density profiles and interaction energies reveals a distinct preference for H2 molecules to adsorb more readily onto graphene surfaces than kaolinite surfaces. However, self-diffusion results demonstrate that H2 molecules interact relatively weakly with both substrate types. Further insights are provided by velocity autocorrelation functions, emphasizing the occurrence of wall-mediated collisions as H2 molecules diffuse along the pore surfaces, particularly within kaolinite. This highlights the significance of surface roughness in mitigating H2 loss via diffusion in subsurface nanopores, given the small molecular size of H2 and its limited interactions with both organic and inorganic materials. Furthermore, the results demonstrate that self-diffusion coefficients in both pore types increase with pore size and decrease with pressure. Notably, surface composition plays a critical role in low-pressure environments, with self-diffusion coefficients beginning to converge beyond a pressure of 100 atm. Self-diffusion coefficients also become less sensitive to slit aperture beyond a pressure of 50 atm. In high-pressure environments, hydrogen transport is governed by thermal collisions between gas molecules, leading to negligible property variations between pore types. These findings hold significance in the investigation of efficient H2 storage within porous media and caprock formations.

A pore-scale numerical framework for solute transport and dispersion in porous media

Pore-scale modeling plays a crucial role in understanding and upscaling solute transport behavior in porous media. Direct simulation offers the highest fidelity in resolving pore-scale fluid flow and mass transfer, nevertheless, with unacceptable computational costs for practical applications. Pore network models (PNM), on the other hand, provide an efficient alternative but with reduced accuracy in representing transport dynamics. In this study, we propose a new framework of pore network models that ensures both accuracy and efficiency, which reproduces the pore-scale shear dispersion effect by utilizing the pore-scale shear dispersion coefficient to calculate the diffusive mass exchange rate between network elements. The coefficient is determined based on the extension of Taylor-Aris theory that expands the classical Taylor-Aris theory to encompass the pre-asymptotic regime. Additionally, the framework adopts a physically representative pore network, where the conduit length and volume of network elements are determined based on local resistance equivalence. After verifying its accuracy and reliability, we conduct a series of numerical cases on tube networks, sphere packs, and sand packs. The breakthrough curves and concentration profiles obtained from our new model show good agreement with direct simulation results and experimental data, while the simulation outcomes of the models that rely on the molecular diffusion coefficient or Taylor dispersion coefficient for local mass exchange may exhibit significant errors. We finally demonstrate that the significance of pore-scale shear dispersion on solute transport weakens for tube networks with increasing degrees of geometrical disorder. The proposed model provides an accurate and efficient numerical framework for the study of solute transport and dispersion in porous media.

A synthetic microplastic fiber-manufacturing method and analysis of airborne microplastic fiber transport behavior in porous media.

Long-term environmental contamination through microplastic (MP) exposure remains poorly understood and may pose economic and geochemical threats. Notably, only a few studies have been conducted on MP contamination of soils. This study investigated the migration of AMP fibers and their influence on water flow rates through porous media. Multiple columns with diameters of 5 cm and water flow rates of 3 ml/min were filled with glass beads or sand. The particle sizes varied between 3 mm for glass beads and 1-2 or 2-4 mm for sand. A method on how to artificially manufacture MP fibers with sizes ranging from 500 to 1000 μm representing AMP fibers occurring in the environment is introduced. The MP fibers were then introduced into water at varying concentrations that were reported in previous studies. The results revealed that regardless of their concentration, the MP fibers suspended in the water did not clog the porous media. In fact, although the fibers penetrated and accumulated in the soil, they did not disrupt the water flow. We recommend that future research focuses on using MP particles with varying densities and at lower concentrations, to prevent flocculation and increase the experiment run time.

Prediction of diffusional conductance in extracted pore network models using convolutional neural networks

Pore network modeling (PNM) based on networks extracted from tomograms is a well-established tool for simulating pore-scale transport behavior in porous media. A key element of this approach is the accurate determination of pore-to-pore conductance values, which is a complex task that greatly affects the accuracy of flow and diffusive mass transport studies. Classic methods of conductance estimation based on analytical solutions and shape factors only apply to simple pore geometries, whereas real porous media contain irregular-shaped pores. Although direct numerical simulations (DNS) can accurately estimate conductance considering pores' real morphology, it has a high computational cost that becomes infeasible for large tomograms. The present work remedies this problem using a deep learning (DL) approach, with a specific focus on diffusional transport which has received less attention than hydraulic conductance. A convolutional neural network (CNN) model was trained to estimate diffusive conductance of PNM elements from volumetric images of porous media. The developed framework estimates the diffusive conductance by analyzing individual pore-to-pore 3D images isolated from the tomogram to fully capture the topology and shapes. A key outcome of the present work is that only images of the pore regions are used as input data, avoiding excessive preprocessing time for data preparation. The results of the diffusive conductance prediction show good agreement with the test data obtained by DNS method, with 0.94 R2 prediction accuracy and a speedup of 500x in prediction runtime.

A Closer Look: High-Resolution Pore-Scale Simulations of Solute Transport and Mixing Through Porous Media Columns

Mixing is pivotal to conservative and reactive transport behaviors in porous media. Methods for investigating mixing processes include mathematical models, laboratory experiments and numerical simulations. The latter have been historically limited by the extreme computational resources needed for solving flow and transport at the microscopic scale within the complex pore structure of a three-dimensional porous medium, while dealing with a sufficiently large domain in order to generate meaningful emergent continuum-scale observables. We present the results of such a set of virtual column experiments, which have been conducted by taking advantage of modern high-performance computing infrastructure and Computational Fluid Dynamics software capable of massively parallel simulations. The computational approach has important advantages such as full control over the experimental conditions as well as high spatial and temporal resolution of measurements. Hydrodynamic dispersion results agree with the empirical and theoretical literature and link dispersivity to median grain size, while elucidating the impact of grain size variability on the critical Péclet number. Reactive transport results also indicate that the relative degree of incomplete mixing is related to the granular material’s mean hydraulic radius and not directly to the median grain size. When compared to a well-known laboratory experiment with similar configuration, less incomplete mixing is observed in our simulations. We offer a partial explanation for this discrepancy, by showing how an apparent nonlinear absorbance–concentration relationship may induce laboratory measurement error in the presence of local concentration fluctuations.

10-m long slim sandpack experiments to investigate gel system transport behavior in porous media

10-m long slim sandpack experiments to investigate gel system transport behavior in porous media

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media under various chemical conditions

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media were elucidated via column experiments under a series combination of electrolytes, pH, and humic acid (HA) conditions. Fragmental PET microplastics showed low mobility in porous media with a small mass recovery rate (<50.1%) even under unfavorable retention conditions. The electrolyte, pH, and HA showed combined impact on PET microplastic transport. PET microplastics mobility was enhanced with decreasing electrolyte concentration, increasing pH, and increasing HA concentration. Basic properties (e.g. destiny and shape) of PET microplastics showed stronger effect on their transport behaviors in porous media rather than the experimental chemical conditions. In general, both environmental factors and basic properties played important roles in controlling the retention and transport of PET microplastics in porous media. A numerical model considering the second order kinetic deposition sites was applied to depict the retention and transport of PET microplastics in porous media. Model simulations well matched the experimental breakthrough curves. Given the fragmental PET microplastics have more realistic and irregular shapes, results from this study can improve present knowledge of the environmental fate and risk of microplastics in underground soil and water systems.

Insights into the Effects of Salinity on the Transport Behavior of Polymer-Enhanced Branched-Preformed Particle Gel Suspension in Porous Media

The branched-preformed particle gel (B-PPG) is a novel viscoelastic particle gel used for improving sweep efficiency and enhancing oil recovery in a heterogeneous mature reservoir. To improve the performance of B-PPG, partially hydrolyzed polyacrylamide (HPAM) is used to increase the viscosity and to prepare a homogeneous B-PPG suspension. Although some encouraging progress has been made in the application of polymer-enhanced B-PPG suspension, its transport behavior in porous media is still unclear, which is crucial for its application in enhanced oil recovery (EOR) in a heterogeneous reservoir. Due to the complex reservoir condition of different brine salinities, the physiochemical property of polymer-enhanced B-PPG suspension as well as its transport behavior in porous media can be affected, which may lead to unsatisfactory results. Understanding the effects of salinity on the transport behavior of polymer-enhanced B-PPG suspension in porous media is of vital importance in figuring out the flow behavior and improving the sweep efficiency in the mature reservoir. In this study, the effects of salinity on the swelling ratio, particle size, viscosity property, and suspension stability of B-PPG and polymer-enhanced B-PPG suspension were studied. Meanwhile, sand pack flow experiments were conducted to study the transport behavior of polymer-enhanced B-PPG suspension in porous media. The results show that when the brine salinity increases, the swelling ratio and particle size of B-PPG, as well as the viscosity and the suspension stability of polymer-enhanced B-PPG suspension all demonstrate a decreasing trend. In the range of 3550–10 651 mg·L–1, as the brine salinity increases, the resistance factor decreases and the transportation of polymer-enhanced B-PPG suspension in porous media becomes easier. In this case, the ratio of swollen B-PPG particle diameter to the pore throat diameter turns out to be the determining factor that governs the transport behavior. However, when the brine salinity is higher than 10 651 mg·L–1, with the increase of brine salinity, the resistance factor increases. As a result, the effects of viscosity and suspension stability of polymer-enhanced B-PPG suspension become more prominent.

Data-driven prediction and analysis method for nanoparticle transport behavior in porous media

Engineering nanoparticles, as one of the application tools of nanotechnology, their transport behavior is closely related to applications such as reservoir sensing and environmental protection. Therefore, it is necessary to develop a general method to predict and analyze the nanoparticle transport behavior. In this paper, a data-driven prediction and analysis method for nanoparticle transport behavior in porous media is proposed. Firstly, a dataset of nanoparticle transport containing 411 samples is established, in which the missing data are effectively filled by random forest combining one-hot encoding. Then, a categorical boosting algorithm combined with synthetic minority oversampling technique is used to predict the retention fraction and retention profile. Finally, the Shapley additive explanation (SHAP) method is adopted to analyze feature significance. The results show that the proposed method has good performance on the prediction of nanoparticle transport behavior which is described by retention fraction and retention profile. At the same time, the interpretability of the SHAP method in analyzing nanoparticles transport behavior is also verified, which provides a new perspective for the further research and application.

Effects of phosphate on the transport of graphene oxide nanoparticles in saturated clean and iron oxide-coated sand columns

In this study, transport behaviors of graphene oxide (GO) in saturated uncoated (i.e., clean sand) and goethite-coated sand porous media were examined as a function of the phosphate. We found that phosphate enhanced the transport of GO over a wide range of solution chemistry (i.e., pH 5.0–9.0 and the presence of 10 mmol/L Na+ or 0.5 mmol/L Ca2+). The results were mainly ascribed to the increase of electrostatic repulsion between nanoparticles and porous media. Meanwhile, deposition site competition induced by the retained phosphate was another important mechanism leading to promote GO transport. Interestingly, when the phosphate concentration increased from 0.1 to 1.0 mmol/L, the transport-enhancement effect of phosphate in goethite-coated sand was to a much larger extent than that in clean sand. The observations were primarily related to the difference in the total mass of retained phosphate between the iron oxide-coated sand and clean sand columns, which resulted in different degrees of the electrostatic repulsion and competitive effect of phosphate. When the background solution contained 0.5 mmol/L Ca2+, phosphate could be bind to sand/ goethite-coated sand surface by cation bridging; and consequently, promoted competition between phosphate and nanoparticles for deposition sites, which was an important mechanism for the enhanced effect of phosphate. Moreover, the DLVO theory was applicable to describe GO transport behaviors in porous media in the absence or presence of phosphate. Taken together, these findings highlight the important status and role of phosphate on the transport and fate of colloidal graphene oxide in the subsurface environment.

Effects of flow-interruption on the bacteria transport behavior in porous media

Attachment is an important strategy for microorganisms to survive, grow, and perform biogeochemical functions in soil and groundwater systems. This study investigated the effect of flow-interruption (FI) that is common in subsurface environments on bacterial attachment/detachment using a metal-reducing bacterium Shewanella oneidensis strain (MR1) as an example. Column experiments and one dimensional bacterial transport models were performed by varying flow interruption duration, fluid ionic strength, and solid grain surface electrostatic properties with a goal to understand the effect of FI on bacterial attachment/detachment. The results indicated that MR1 generally behaved as colloidal particles in transport and attachment/detachment under continuous flow conditions. However, the FI events induced a significant release of MR1 in both injection and elution phases, showing a peak MR1 concentration, which was higher than that in the injecting solution, immediately after the FI events. The peak MR1 concentrations were higher in systems with lower adhesive forces between bacteria and solid grains, a lower attachment site capacity in porous media, and a longer FI duration. The diffusive release of the previously attached bacteria during the FI events and the momentum force when flow re-started immediately after the FI events were likely the mechanisms leading to bursting release of bacteria with the release concentrations higher than that in the influent solutions. The results have important implication for understanding bacterial migration and attachment, and their subsequent functions, especially in dynamic hydraulic environments such as in hyporheic zones or in soils subject to dynamic changes in infiltration rates under for example extreme precipitation and drought conditions.

Different surface charged plastic particles have different cotransport behaviors with kaolinite ☆particles in porous media

The wide utilization of plastic related products leads to the ubiquitous presence of plastic particles in natural environments. Plastic particles could interact with kaolinite (one type of typical clay particles abundant in environments) and form plastic-kaolinite heteroaggregates. The fate and transport of both plastic particles and kaolinite particles thus might be altered. The cotransport and deposition behaviors of micron-sized plastic particles (MPs) with different surface charge (both negative and positive surface charge) with kaolinite in porous media in both 5 and 25 mM NaCl solutions were investigated in present study. Both types of MPs (negatively charged carboxylate-modified MPs (CMPs) and positively charged amine-modified MPs (AMPs)) formed heteroaggregates with kaolinite particles under both solution conditions examined, however, CMPs and AMPs exhibited different cotransport behaviors with kaolinite. Specifically, the transport of both CMPs and kaolinite was increased under both ionic strength conditions when kaolinite and CMPs were copresent in suspensions. While, when kaolinite and positively charged AMPs were copresent in suspensions, negligible transport of both kaolinite and AMPs were observed under examined salt solution conditions. The competition deposition sites by kaolinite (the portion suspending in solution) with CMPs-kaolinite heteroaggregates led to the increased transport both CMPs and kaolinite when both types of colloids were copresent. In contrast, the formation of larger sized AMPs-kaolinite heteroaggregates with surface charge heterogeneity led to the negligible transport of both kaolinite and AMPs when they were copresent in suspensions. The results of this study show that when plastic particles and kaolinite particles are copresent in natural environments, their interaction with each other will affect their transport behaviors in porous media. The alteration in the transport of MPs or kaolinite (either increased or decreased transport) is highly correlated with the surface charge of MPs.

Cotransport and deposition of colloidal polystyrene microplastic particles and tetracycline in porous media: The impact of ionic strength and cationic types

The cotransport behaviors of colloidal polystyrene microplastic particles (PSMPs) and tetracycline (TC) (20 mg/L) were investigated in saturated porous media in KCl and CaCl2 solutions of various ionic strengths (1, 10, 50, 100 mM). Furthermore, the effects of TC concentration (0, 1, 5, 10, 20 mg/L) on the cotransport behaviors of PSMPs and TC in 100 mM KCl solution were assessed. The cotransport behaviors were analyzed by comparing the individual transport behaviors of PSMPs or TC. When cotransported, the presence of TC (20 mg/L) slightly inhibited PSMPs mobility in K+ solutions (the C/C0 decreased in the range of 0–5.9%), but facilitated it in Ca2+ solutions (the C/C0 increased in the range of 6.7–42.6%). In KCl solutions, although the presence of TC (PSMPs) did not significantly affect the transport behaviors of PSMPs (TC), the attachment efficiencies of both PSMPs and TC showed a non-linear and non-monotonic change with increase in ionic strength. However, in CaCl2 solutions, the effects of TC (PSMPs) on the transport behaviors of PSMPs (TC) were remarkable and a non-linear non-monotonic change was observed. The adsorption of TC on PSMPs might play a critical role during the cotransport. Thus, the balance between the transport-inhibiting (e.g., the reduction in electrostatic repulsive force) and transport-facilitating effects (e.g., the effects on hydrophilicity/hydrophobicity of PSMPs due to TC adsorption) may be responsible for the observed changes. Overall, the results demonstrated that the cotransport behaviors of PSMPs and TC were more complicated than their individual transport behaviors in porous media, which might vary considerably with environmental conditions. This work could greatly improve our understanding of complex cotransport behaviors and environmental risk of PSMPs.

Application of Fractional Flow Theory for Analytical Modeling of Surfactant Flooding, Polymer Flooding, and Surfactant/Polymer Flooding for Chemical Enhanced Oil Recovery

Fractional flow theory still serves as a powerful tool for validation of numerical reservoir models, understanding of the mechanisms, and interpretation of transport behavior in porous media during the Chemical-Enhanced Oil Recovery (CEOR) process. With the enrichment of CEOR mechanisms, it is important to revisit the application of fractional flow theory to CEOR at this stage. For surfactant flooding, the effects of surfactant adsorption, surfactant partition, initial oil saturation, interfacial tension, and injection slug size have been systematically investigated. In terms of polymer flooding, the effects of polymer viscosity, initial oil saturation, polymer viscoelasticity, slug size, polymer inaccessible pore volume (IPV), and polymer retention are also reviewed extensively. Finally, the fractional flow theory is applied to surfactant/polymer flooding to evaluate its effectiveness in CEOR. This paper provides insight into the CEOR mechanism and serves as an up-to-date reference for analytical modeling of the surfactant flooding, polymer flooding, and surfactant/polymer flooding CEOR process.

Cotransport and deposition of biochar with different sized-plastic particles in saturated porous media

Plastic particles recently are reported to be ubiquitous in natural environments, while biochar is widely employed as an amendment into natural environments e.g. soil for pollution remediation. It is highly likely their transport behaviors in porous media would be altered due to interaction with each other. In this study, the cotransport and deposition behaviors of biochar and plastic particles (0.02 μm nanoplastics (NPs), 0.2 μm and 2 μm micrometer-plastics (MPs)) in quartz sand were investigated at both low (5 mM) and high ionic strength (25 mM) in NaCl solutions at pH 6. The results demonstrated that smaller sized plastic particles (0.02 μm NPs and 0.2 μm MPs) increased biochar transport under both 5 and 25 mM NaCl solutions, while large plastic particles (2 μm MPs) increased biochar transport in 5 mM NaCl solutions yet decreased biochar transport in 25 mM NaCl solutions. For all sized plastic particles, biochar significantly decreased their transport at both low (5 mM) and high (25 mM) ionic strengths in NaCl solutions. The change of zeta potentials of biochar due to heteroaggregation with plastic particles, and the steric repulsion induced by the suspended plastic particles contributed to the enhanced biochar transport with the copresence of smaller sized plastic particles (0.02 μm NPs and 0.2 μm MPs). While, the cotransport of biochar with 2 μm MPs due to their heteroaggregation contributed to the varied transport behaviors of biochar observed at low and high ionic strength with the copresence of 2 μm MPs. The formation of plastic particles-biochar heteroaggregates drove to the decreased transport of all three different sized plastic particles with the copresence of biochar. Considering the coexistence of biochar and plastic particles in natural environment, they would interact with each other (form heteroaggregates) and thus lead to the change of transport behaviors in porous media.

Impact of pore structure and morphology on flow and transport characteristics in randomly repacked grains with different angularities

The flow and transport behaviors in porous media are closely linked to the structure and morphology of the pore space. A fundamental objective of most studies of porous media is to link the pore structure to the hydraulic functions, such as the permeability, capillary pressure and diffusivity, which are necessary for engineering applications. In this paper, an attempt is made to build a direct link between the hydraulic functions and the morphological measures of diverse porous media. Porous columns with different structures and morphologies are generated by randomly packing grains with different shapes and sizes. The pore structure of the repacked porous media is visualized through X-ray computed tomography and quantified by a series of parameters, including the set of Minkowski functionals, diverse characteristic pore sizes, geometric tortuosity and fractal dimension. The intrinsic permeability, molecular diffusivity and apparent thermal conductivity of the repacked porous media are simulated numerically. The Minkowski functionals have the capacity to characterize the microscale complex pore domain of the porous media in a macroscale way. A good linear relationship is shown among the effective pore size, nominal opening dimension and critical pore neck size obtained from the morphological analysis regardless of the shapes and sizes of the grains. The three different pores may serve as the characteristic pore correlation to the intrinsic permeability. The Kozeny-Carman equation can be used to mimic the intrinsic permeability and to serve as a quality-control tool for porous media with different grain angularities. A topologically based model can generally provide a single relationship for porous media randomly repacked with grains of different angularities. The molecular diffusivity of angular grains is found to be larger than that of round ones. The molecular diffusivity is linearly related to the porosity and fractal dimension. Porous media repacked with round grains tend to attain denser packing, a higher number of contacts per unit volume and higher thermal conductivity than media packed with angular particles. The apparent thermal conductivity has a negative linear correlation to the porosity and fractal dimension of porous media with different grain morphologies.

Mobility and transport behavior of lead in agricultural soils

Abstract The description of contaminant transport behavior in porous media is essential to optimally manage soils and subsurface aquifers, and to deal with chemical pollution in these resources. This study was conducted to examine the transport behavior of Pb through soil columns at different concentrations of Pb. Soil columns were collected from three different agricultural fields, namely, close canopy cocoa (CCC), open canopy cocoa (OCC) and an arable field grown with maize. The soils from all the three fields had a loamy sand texture. Soil from the CCC field had the best structure as evinced by the high total porosity (f), macroporosity (fm), soil organic carbon (SOC), and saturated hydraulic conductivity (Ks), and low bulk density (BD). The results indicated that high concentrations of applied Pb resulted in high concentrations of Pb in the effluents. In addition, the transport of Pb through the soil columns were found to be significantly affected by SOC, f, fm, Ks, and BD. The highest rates of Pb leaching at all application concentrations were observed in the CCC soil, and the least in the arable field.

Cotransport and Deposition of Iron Oxides with Different-Sized Plastic Particles in Saturated Quartz Sand.

The present study was designed to investigate the cotransport and deposition of different-sized plastic particle from nano- (0.02 μm) to micrometer-scale (0.2 and 2 μm) with goethite and hematite (two types of representative iron oxides abundant in natural environment) in porous media at both low (5 mM) and high ionic strength (25 mM) in NaCl solutions. We found that through different mechanisms (i.e., modification of surface properties of iron oxides, steric repulsion, or alteration in deposition sites on quartz sand), different-sized plastic particles induced different effects on the transport and deposition behaviors of iron oxides in quartz sand. Likewise, via different mechanisms such as change of surface properties or alteration in deposition sites on quartz sand, different transport behaviors for different sized plastic particles induced by the copresence of iron oxides were also observed. The results of this study suggested that cotransport of iron oxides and plastic particles in porous media is far more complex than those of individual colloid transport. Since both plastic particles and iron oxides are ubiquitous presence in natural environment, it is expected that they would interact with each other and thus alter the surface properties, leading to the change of transport behaviors in porous media.

Critical Review of Stabilized Nanoparticle Transport in Porous Media

Over the past few decades, due to the special features (i.e., easily produced, large-surface-area-to-volume ratio, and engineered particles with designed surface properties), nanoparticles have not only attracted great attentions from the oil and gas industry but also had various applications from drilling and completion, reservoir characterization, to enhanced oil recovery (EOR). As sensors or EOR agents, thus, fate and behavior of nanoparticles in porous media are essential and need to be investigated thoroughly. Nevertheless, most of the published review papers focus on particle transport in saturated porous media, and all of them are about steady-state flow conditions. So far, no attempts have been extended to systematically review current knowledge about nanoparticle transport in porous media with single-phase and two-phase flow systems under both steady-state and unsteady-state conditions. Accordingly, this review will discuss nanoparticle transport phenomena in porous media with its focus on the filtration mechanisms, the underlying interaction forces, and factors dominating nanoparticle transport behavior in porous media. Finally, mathematical models used to describe nanoparticle transport in porous media for both single-phase flow and two-phase flow under steady-state and transient flow conditions will be summarized, respectively.