Solutes In Porous Media Research Articles

A perspective view of salt crystallization from solution in porous media: morphology, mechanism, and salt efflorescence.

Salt efflorescence is one of the major hazards to cultural heritages, masonries, and highways etc. It is now generally accepted that damages caused by salt efflorescence are mainly due to continuous cycles of salt crystallization/dissolution or hydration/dehydration in confined spaces. The position where salt efflorescence occurs and its type are closely related to the degree of damages caused by salt efflorescence. It is known that water is the key environmental factor determining the salt crystallization position. But influence of the correlation between water supply and evaporation on the position of salt crystallization is still not clearly understood. In this work, a set of experiments are designed to investigate salt efflorescence in porous matrix. It is found that the types and positions of salt efflorescence have little to do with nucleation, but are mainly governed by crystal growth, which is controlled by the rates of water evaporation, water and salt supply, capillary forces and surface properties of the porous matrices.

MATHEMATICAL MODEL AND NUMERICAL METHODS OF FILTRATION PROCESSES OF LIQUID SOLUTIONS

Filtration processes of liquid solutions are fundamental in many natural and industrial applications, such as environmental protection, chemical engineering, water purification, and petroleum extraction. This article develops a mathematical model for describing filtration processes and explores various numerical methods for solving the governing equations. The model is based on Darcy’s law, continuity equation, and constitutive relations of liquid solutions in porous media. Numerical methods, including finite difference, finite element, and finite volume approaches, are discussed with applications to various filtration scenarios. We also provide analysis of the stability, convergence, and efficiency of these methods.

Transient flow of electrolyte solution in porous media with membranes fitted at the upper wall surface and lower charged surface

Transient flow of electrolyte solution in porous media with membranes fitted at the upper wall surface and lower charged surface

PERIODIC FOAMING DURING SELECTIVE ISOLATION OF HIGHLY PERMEABLE CHANNELS OF POROUS MEDIUM

Selective isolation of watered interlayers by forming barriers formed by highly viscous gels or insoluble precipitates does not always lead to the desired results. Field experience confirms that at some distance from the formed barrier, the filtration flow restores its configuration and the water injected into the formation again moves through highly permeable channels. An increase in the efficiency of flow deflection can be achieved by creating not a single barrier, but a whole sequence of alternating deep-penetrating insulating barriers, separated from each other by a certain distance in highly permeable pores. The paper presents the results of studies of quasi-periodic foaming in order to control mobility under conditions of selective isolation of water in pore channels of high permeability. Foaming occurs due to the in-bulk reaction between concentrated aqueous solutions of gas-generating and gas-generating solutions. Flow pattern of injected aqueous solutions of foaming reagents along current tubes is investigated. The task is to determine the space-time distribution of reagents in given zones of the porous medium. The problem of establishing the correlation between the spatial distribution of the gas formation zone and the dynamics of the gas formation process over time on the one hand, as well as the concentration of reactants, the diffusion rate (mutual diffusion), the gas generation rate and the probability of nucleation on the other hand was solved. The degree of flow blockage in highly permeable zones of the formation depends on the rate of in-situ foam generation and the simulation consists in the fact that it is similar to the law of filtration with a limiting gradient. The paper discusses the process of quasi-periodic gas formation during the movement of mixing solutions in porous media. In stationary filtration in a homogeneous porous medium, the process is described by the proposed system of equations. A system of equations is proposed that describes the movement of a liquid taking into account adsorption of reagents, diffusion and dynamics of the foaming reaction. The results obtained can serve as the basis for developing a method for controlling the water cut of porous media during waterflooding of oil formations. This, in turn, leads to the leveling of the displacement front and an increase in the completeness of coverage.

Harnessing elastic instabilities for enhanced mixing and reaction kinetics in porous media

Turbulent flows have been used for millennia to mix solutes; a familiar example is stirring cream into coffee. However, many energy, environmental, and industrial processes rely on the mixing of solutes in porous media where confinement suppresses inertial turbulence. As a result, mixing is drastically hindered, requiring fluid to permeate long distances for appreciable mixing and introducing additional steps to drive mixing that can be expensive and environmentally harmful. Here, we demonstrate that this limitation can be overcome just by adding dilute amounts of flexible polymers to the fluid. Flow-driven stretching of the polymers generates an elastic instability, driving turbulent-like chaotic flow fluctuations, despite the pore-scale confinement that prohibits typical inertial turbulence. Using in situ imaging, we show that these fluctuations stretch and fold the fluid within the pores along thin layers ("lamellae") characterized by sharp solute concentration gradients, driving mixing by diffusion in the pores. This process results in a [Formula: see text] reduction in the required mixing length, a [Formula: see text] increase in solute transverse dispersivity, and can be harnessed to increase the rate at which chemical compounds react by [Formula: see text]-enhancements that we rationalize using turbulence-inspired modeling of the underlying transport processes. Our work thereby establishes a simple, robust, versatile, and predictive way to mix solutes in porous media, with potential applications ranging from large-scale chemical production to environmental remediation.

Enhancing heavy‐oil displacement efficiency through viscoelasticity of polymer solution by investigating the viscosity limit of crude oil: An experimental study

AbstractThe world is rich in ordinary heavy‐oil resources. Exploring the limit of the crude oil viscosity limits can further expand the application of polymer flooding technology in heavy‐oil reservoirs and improve the development efficiency of heavy‐oil reservoirs. On the basis of the polymer flooding that has been implemented in the Bohai offshore oilfield, this study characterized the in situ viscoelasticity of the polymer solution SNF3640C. We compared the polymer flooding and glycerol flooding performance in low‐viscous oil reservoirs (with a viscosity of 6.5 cp) and high‐viscous oil reservoirs (with a viscosity of 65 cp) by conducting microscopic dead‐end experiments and macroscopic core‐flooding experiments, and then analyzing the impact of polymer's viscoelasticity on the oil displacement efficiency of heavy oil. Finally, multiple crude oils with a wide range of viscosity were used to explore the crude oil viscosity limits under which the efficiency of heavy‐oil displacement could be improved through polymer viscoelasticity. The results demonstrate that: (1) the SNF3640C polymer solution can exhibit a certain degree of viscoelasticity in deep formation. At a distance of 140 m from the wellbore in the reservoir, a solution with a concentration of 1500 mg/L can still have a first normal stress difference of 2.5 Pa. Polymers can effectively improve the efficiency of heavy‐oil displacement through elastic action. (2) The viscosity limit that can improve the efficiency of heavy‐oil displacement under current experimental conditions does not exceed 5486 cp. The efficiency of polymer flooding for crude oil has decreased to 31.68%, and the contribution of elastic flooding is only 1.5%. The research method of using viscous glycerol as a comparison to demonstrate the contribution of polymer elasticity to oil displacement effectiveness effectively solves the problem of isolating the contribution by polymer solution's viscosity and elasticity, and clarifies the development direction of polymer flooding for developing heavy crude oil. Enhancing the elastic effect of polymer solution in porous media can increase the viscosity range of polymer flooding heavy oil.

Simulation and experimental study of heat-moisture-solute transfer during drying process of porous media

Fruits and vegetables, being typical porous media, allow for the migration of nutrients (solutes) and the transport of moisture simultaneously during the drying process. To reveal the migration mechanism of heat-moisture-solute during the drying process of porous media, a comprehensive mathematical model was established that accounts for the coupled phenomena of heat and moisture transfer, along with solute migration. The model was simulated using COMSOL to provide insights into these complex interactions. Hot-air drying experiments were conducted using apple slices as the subject to validate the accuracy and reliability of the model. The simulation results and experimental results of temperature, moisture content, and sugar concentration were in good agreement. The findings demonstrate that as the drying process progresses, the interface between temperature, moisture gradients, and sugar concentration shifts from the outer layers toward the inner regions. We investigated the effects of hot air temperature, thickness, and porosity on the heat-moisture-solute transfer in porous media. The results provide support for accurately predicting the migration and transport mechanisms of solutes in porous media.

Heterogeneous ice nucleation of salt solution in porous media.

Water ubiquitously exists with dissolved salt in both natural and engineered porous media, such as soil, rock, concrete, and tissue; therefore, its freezing temperature depression behavior is of particular interest to various scientific communities tackling with mechanics and physics of porous media. To date, it remains elusive which physical mechanism accounts for its freezing temperature depression and how dissolved ions affect it. Herein, a series of pore-scale experiments were designated to investigate the freezing temperature of salt solutions in tubes with varying pore diameters, pore solution volumes, solid-liquid interfacial areas, ion concentrations, and ion types. The results reveal two main findings: (i) the freezing temperature depression of pore solutions is governed by the heterogeneous ice nucleation (HIN) at the water-solid interface, as evidenced by the observation that the freezing temperature decreases with the decreasing solid-liquid interfacial areas, regardless of pore diameter and pore solution volume; (ii) the dissolved salts alter HIN processes via changing the osmotic potential across the ice embryo-liquid water interface, as indicated by the observation that the freezing temperature is mainly determined by the salt concentration irrespective of salt types. Furthermore, the classical nucleation theory model is adapted for the freezing behavior of pore solutions by including an osmotic potential term. The model shows excellent performance in capturing experimental data with various pore solution concentrations, further substantiating the HIN as the physical mechanism governing pore solution freezing.

A numerical model for the transport and drying of solutions in thin porous media — Coffee-stain effect and solute ring formation

We have developed a comprehensive numerical model for the transport and drying of solutions in thin porous media that consist of permeable fibers such as paper. We explicitly account for the gas-phase transport dynamics. Moreover, we introduce an empirical relation for the concentration- and molecular-weight dependence of the pore-fiber transport rate of the solutes. These two key elements enable us for the first time to realistically model two important phenomena relevant to inkjet printing technology. The first is the equivalent of the coffee-stain effect for dilute solutions in porous media. The second is the formation of solute rings for concentrated aqueous mixtures of compounds with a molecular weight significantly above that of water. Whereas the first is governed by spatially non-uniform solvent evaporation, the second case is dominated by solvent-mediated pore-fiber transport. We achieved a good qualitative agreement with the available experimental data.

Flow characteristic of polymer solutions in porous media: Influence of the molecular weight and concentration

Flow characteristic of polymer solutions in porous media: Influence of the molecular weight and concentration

Transfer of Metals under Hydrothermal Conditions in the Form of Colloidal Particles and Supersaturated True Solutions

Colloids of metals have been studied much more poorly in hydrothermal solutions than in surface and underground waters. Nevertheless, literature data indicate that colloidal particles containing metals are present in hydrothermal minerals, in geogas, in groundwaters above orebodies, in fluid inclusions of minerals, and in geothermal solutions. These particles are usually thought to be formed at nucleation in supersaturated solution, which is generated in conversion reactions of minerals or when fluids boil. Published experimental data confirm that colloidal particles can be formed and preserved in hydrothermal conditions. Experimental data on the filtration of supersaturated and colloidal solutions in porous media at elevated temperatures are still too scarce to enable a comprehensive and reasonably accurate assessment of the mobility of colloidal particles under these conditions. The involvement of colloids in the hydrothermal ore-forming process is most clearly manifested at formation of rich epithermal Au deposits. The example of a quartz geothermometer is employed to demonstrate that metals can be transferred in true supersaturated solution, and this mechanism may be even more efficient than colloidal transfer. Metals can thus be transferred in the hydrothermal process in significantly higher concentrations than it follows from the traditional approach based on equilibrium thermodynamics.

Advancing the knowledge of solute transport in the presence of bound water in mixed porous media based on low-field nuclear magnetic resonance

Bound water (BW) has significant effects on the physical and chemical properties of soils and other geologic formations. However, little is known about its effect on the non-Fickian transport of solute in porous media. This paper investigated the effect of BW on the non-Fickian solute transport characteristics in mixed porous media. Different porous media of quartz sand with variable contents of powdered minerals were prepared. The low-field nuclear magnetic resonance (LF-NMR) was used to quantitatively characterise BW and its spatial distribution. Then solute transport experiments were conducted in different prepared porous media and the measured breakthrough curves (BTCs) were analysed using the advection–dispersion equation (ADE), mobile-immobile (MIM) and continuous time random walk (CTRW) models. The results revealed that all measured BTCs exhibited the characteristics of early arrival and late-time tailing. However, stronger non-Fickian characteristics were observed as BW increased in content, indicating that BW influenced the non-Fickian transport of the solute. The optimised immobile water fraction of the MIM model consistently increased with increasing estimated BW fraction. Moreover, the coefficient of mass transfer rate (α) of MIM decreased as BW increased, meaning that the solute exchange between the mobile and immobile fluids became slower and consequently yielded strongly tailed BTCs. From the CTRW model, the solute transport velocity (vCTRW) increased with increasing BW, leading to a reduction in the breakthrough time of the solute. An increase in BW yielded a decreasing power law exponent (βCTRW) of the CTRW model, implying an enhancement of the non-Fickian transport characteristics. Furthermore, the porous media with BW<16.4% showed moderately non-Fickian solute transport whereas those with BW≥16.4% exhibited highly non-Fickian solute transport.

IDENTIFICATION OF TRANSPORT PARAMETERS FOR THE SOLUTE FILTRATION THROUGH POROUS MEDIA WITH CLOGGING

The transport of highly concentrated solutions in porous media was studied both numerically and experimentally. For numerical modeling we used a mobile-immobile (MIM) approach that considers clogging phenomenon. The impurity transition between the mobile and immobile phases was defined by second-order Langmuir kinetics. Kozeny-Carman expression modeled the clogging. The model has four phenomenological parameters which cannot be measured directly. These parameters were identified by minimization of the cost function, which is the squared distance between experimental and numerical data. Dependencies of concentration and mass flux at the outlet were analyzed. Twenty-five different experiments were conducted, and it was shown that transport parameters do not depend on impurity concentration or pressure drop between the ends of the column.

Characterization of Nonlinear Viscoelastic Properties of Enhanced Oil Recovery Polymer Systems Using Steady-Shear Rheometry

SummaryEnhanced oil recovery (EOR) polymer systems such as hydrolyzed polyacrylamide (HPAM) solutions flowing in porous media at high fluxes were reported to cause shear-thickening, a nonlinear viscoelastic (NLVE) phenomenon. Bulk rheological studies are usually performed to characterize the viscous and viscoelastic behaviors of polymer solutions in porous media. To characterize the viscoelastic properties, oscillatory shear rheology based on linear viscoelastic (LVE) data and extensional rheology based on NLVE data have been used. Although both extensional flow and high-speed shear flow can stretch and thicken polymer solutions in a nonlinear fashion, steady-shear rheometry has been used to measure only the viscous and thinning behavior of HPAM systems. In this paper, (a) the thickening ability of HPAM polymer systems formulated with contrasting salinity and molecular weight (MW) concentration is characterized in bulk shear rheometry to analyze if the thickening in the pure shear field correlates with the thickening behavior reported in porous media and other rheometry and (b) the thickening intensity of the polymer solutions of varying salinity concentration in the bulk shear field is compared with the reported mechanical degradation effects in the literature.The shear-thickening index obtained by fitting a power-law model to thickening data in steady-shear rheograms is higher for the high-saline, high-MW low-concentration HPAM systems that have inherently higher nonlinear viscoelasticity. Furthermore, the thickening behavior observed due to salinity variation in bulk steady shear contrasts with linear oscillatory shear behavior but conforms to the thickening behavior observed in porous media and in the extensional field. This signifies that polymer-EOR researchers performing comparative studies on low-salinity and high-salinity polymer floods, and having a shear rheometer at their disposal, must look beyond linear oscillatory rheology and make use of nonlinear steady-shear rheology. There is a direct relation between the shear-thickening index of saline HPAM solutions and their mechanical degradation intensity. This paper shows that the high-speed data in steady-shear rheometry that are usually ignored in EOR literature have useful information and the notion that HPAM solutions are purely thinning in the bulk shear field needs to be reconsidered.

Viscoelastic behavior of dilute polyelectrolyte solutions in complex geometries

In this work, we develop a theoretical model describing the viscoelastic behavior of dilute polyelectrolyte (PE) solutions using Onsager’s variational principle, with the effect of the polyelectrolyte charge and solvent salinity accounted for. The PE molecules are described as finitely extensible charged dumbbells suspended in a solvent containing ionic species which screen the charged sites on the macromolecules. The performance of the model was examined and compared against experimental data in simple flows, accounting for the magnitude of charge on the PE molecules and counterion screening effects. Numerical simulations of the flow past a single cylinder and an idealized porous medium with multiple cylinders were carried out and compared to flow of uncharged polymers in the same geometries to explore the effect of intramolecular electrostatic repulsion on the flow behavior. The extra rigidity offered by the repulsion between the charged monomeric units of the PE, and screening of these charged sites by the ionic species in the solvent led to significantly different behavior in complex flows when compared to that of uncharged polymers. The normal stresses generated in a complex flow show an increase with the polyelectrolyte molecule charge density, whereas enhanced screening of the charged sites by counterions suppresses this effect, showing behavior closer to that of uncharged polymers. Drag on a cylinder placed in the flow and pressure drop across the porous geometry increased with charge density of the molecules, exhibiting rheological behavior in complex geometries not shown by their uncharged counterparts. The results show the effects of the degree of hydrolysis and solvent salinity on the flow behavior of dilute PE solutions in complex geometries and has implications for biological systems in which PE species are commonly encountered, as well as operation of industrial processes such as enhanced oil recovery, which frequently involve the flow of dilute polyelectrolyte solutions in porous media. • Macroscopic flow behavior of dilute polyelectrolyte solutions is investigated. • Onsager’s Variational Principle used for developing model from first principles. • Reformulation of charged dumbbell model for simulating flows in complex geometries. • Polyelectrolyte charge density and solvent salinity influence flow behavior. • Drag coefficients and normal stresses increase with charged nature of molecules.

Experimental and modeling study of hydrophobic associative polyacrylamide for enhanced oil recovery in carbonate reservoir

In this study, hydrophobic associative polyacrylamide (HAPAM) was used in conjunction with the chemical flooding technique in a low-permeability carbonates reservoir. To test the efficacy of the proposed method, both a model and an experiment were created. Experiments were run to compare the relative permeability (Kr) curves, oil recovery rates, and rheological, physical, aging time, and petrophysical features of brine water and polymer flooding in a core. The purpose of these tests was to show how HAPAM can be used to boost oil recovery. Computer Modelling Group (CMG), a simulator, was then used. An oil-and-brine (or HAPAM solution) grid in three dimensions (3D) was developed. The validity of the suggested simulator was established by comparing its results to those obtained from commercial software and from the majority of brine or polymer flooding experiments. The developed simulator was used to undertake additional research into the non-Newtonian flow of brine or polymer solution in porous media. The experimental consequences indicated that the polymer solution has a shear thinning viscosity curve and flow behavior index. Shear thinning, viscosity, shear resistance, aging time, density, surface tension, and interfacial tension, and the water wet relative permeability curve are all improved by the adding 1500 ppm HAPAM to brine water. Moreover, oil recovery was about 80%. There was a strong agreement between the results of the modeling study and the experiments.

Influencing factors for effective establishment of residual resistance factor of polymer solution in porous media

Influencing factors for effective establishment of residual resistance factor of polymer solution in porous media

A baseline study of mineralogical and morphological properties of different size fractions of illite du Puy

The objective of this study is to revisit the mineralogical and physico-chemical properties of illite du Puy material (Puy-en-Velay, France), which is envisaged as a model clay system in the European Joint Programme on Radioactive Waste Management (EURAD) project. This illite material is compared to the raw illite material commonly extracted from the Velay ore site. Both materials were collected and separated into different subfractions (i.e., <0.05, 0.05–0.1, 0.1–0.2, and 0.2–2 μm) to examine the mineralogical heterogeneity. The X-ray diffraction bulk analyses indicated that the observed variability in the literature, in terms of the nature of accessory minerals and the presence of kaolinite, was directly related to the locations of geological sampling. Moreover, the respective mass contributions of the different subfractions were similar for the two materials.Further analyses were performed on the subfractions of the illite used for the EURAD project by utilizing a suite of different techniques. The clay mineralogy was refined as an illite–smectite mixed-layer mineral with a small amount (<5%) of smectite layers. No significant changes in chemical properties or particle lamellarity were observed between the different subfractions. However, the different subfractions displayed a wide range of specific surface areas (i.e., N2 BET surface) and cation exchange capacity values, the latter of which increased by factors of ~3 and ~ 5 from the 0.2–2 μm to the <0.05 μm size fractions, respectively. The EURAD illite and associated subfractions can be considered appropriate material models to be used for the refinement of our understanding of the adsorption and diffusion processes of solutes in porous media made from charged clay particles.

Dilution of Reactive Plumes: Evolution of Concentration Statistics Under Diffusion and Nonlinear Reaction

Concentration fields of solutes in porous media often exhibit large fluctuations, driven by physical and chemical heterogeneity from the pore to the Darcy scale. For many applications, ranging from reactive transport modeling to toxicology, the knowledge of mean concentrations is not sufficient, and quantifying concentration variability is necessary. The probability density function (PDF) of concentration quantifies the frequency of occurrence of concentration values throughout a spatial domain. While evolution equations and analytical solutions for the concentration PDF exist for conservative solutes, less is known about its evolution under the joint action of transport and reaction. In this work, we investigate how dilution of a reactive plume by diffusion affects the statistics of concentrations. While mixing has no effect on first-order reactions, its coupling with nonlinear reactions leads to non-trivial effective kinetics relevant for a broad range of reactive transport problems. We study the evolution of the concentration PDF under diffusion and nonlinear reaction in one spatial dimension, which represents a critical step toward further coupling with heterogeneous advection. We show that the dependence of the scalar dissipation rate on concentration encodes the impact of diffusive transport on the concentration PDF and derive a dynamical equation for its time evolution. Using a weak-coupling approximation for the reaction and diffusion dynamics, we derive analytical predictions for the concentration PDF and its moments. Our results provide new insights into how diffusion and reaction control concentration variability and open new opportunities for coupling mixing models with chemical reactions.

Analysis of the importance of the dispersion coefficient depending on the distance for the transport of solute in porous media

Analysis of the importance of the dispersion coefficient depending on the distance for the transport of solute in porous media