HS8.1.2

Hydrocarbon contamination is among the most frequent sources of soil and water environmental impacts. Many remediation methods have been implemented to clean up the contaminated environment so far. In-Situ Chemical Oxidation has attracted attention as it has shown efficiency in contaminants removal and cost-effectivity. In addition, soil washing by surfactant foam has been recently proven as a promising method. The combination of these two methods can take the advantage of oxidation while eliminating the challenges regarding the poor distribution of treatment fluid in a heterogeneous porous media. The ultimate goal of this study is to use surfactant foam for delivering oxidant (persulfate) through diesel-contaminated soil in permafrost. However, the interaction between the surfactant and the oxidant needs to be studied first. A better understanding of the impact of surfactants and oxidants on each other can lead to an optimized process. At the first stage of this study, different concentrations of surfactant solutions (sodium dodecyl sulfate: cocamidopropyl betaine in a mass ratio of 1:1) were mixed with a constant persulfate concentration activated with alkali, in absence of hydrocarbon. The preliminary results showed that the initial concentration of the oxidant has no significant effect on its decomposition rate. Also, as the concentration of surfactant was increased above the Critical Micellar Concentration (CMC), the persulfate decomposition rate decreased, likely due to the formation of micelles. However, as the micelles started to be destroyed, the decomposition rate of the oxidant increased gradually and the highest rate was observed when the concentration of surfactant was close to the CMC. When no micelle was left in the solution, the decomposition rate of the oxidant waned to a low value. Thus, coupling the surfactant and the oxidant can be effective for the degradation of hydrocarbon contaminants. Micelles bring part of the hydrocarbon into the aqueous phase and then the micelles are destroyed by the oxidant that can also degrade the hydrocarbon effectively over time.

How to cite: Abolhosseini, P., Robert, T., Martel, R., and Kaur Brar, S.: Effect of surfactant concentration on the decomposition rate of alkaline activated persulfate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2112, https://doi.org/10.5194/egusphere-egu22-2112, 2022.

Natural porous systems, like soils and aquifers, are physically and chemically highly heterogeneous. Microorganisms inhabiting these environments are therefore exposed to heterogeneous fluid flow velocities and nutrient landscapes. Bacteria capable of biasing their motion to swim along chemical gradients – known as chemotaxis – profit from their ability to localize and navigate towards nutrient hot spots, such as soil aggregates or plant roots.
We propose a novel experimental microfluidic platform to study chemotaxis at the pore-scale, allowing full optical access to the pore space and simultaneously enabling control over the spatio-temporal availability of nutrients. The microfluidic device contains hydrogel features, acting as nutrient hotspots, embedded in a porous medium, made out of transparent polydimethylsiloxane (PDMS) pillars. Nutrients are transported by diffusion from the access channels through the hydrogel into the porous medium, where they are released. The generated nutrient gradients downstream of the hotspots under flow conditions drive the swimming of chemotactic bacteria.
This approach enables the study of subsurface processes at the pore-scale under more realistic conditions, and shed new light onto the influence of physical and chemical heterogeneity on bacterial dispersion and residence time in the subsurface.

Keywords: porous media, soil, chemotaxis, microfluidics, heterogeneity

How to cite: Stoll, M. F., Stocker, R., and Jimenez-Martinez, J.: A pore-scale study of bacterial chemotaxis with segregated and controlled nutrient sources, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3964, https://doi.org/10.5194/egusphere-egu22-3964, 2022.

Chaotic advection can be created by engineered sequence of extraction and injection of groundwater in aquifers and by creating an engineered oscillatory flow. It has been used in a wide range of applications, including enhancement of degradation during aquifer remediation, in-situ leaching of metals to enhance mining recovery, and dissipation of energy in geothermal systems. Most of these works are based on numerical simulations and little experimental evidence are reported in the literature. In this work, we analyze how an engineered oscillatory flow can favor mixing-induced precipitation, increasing the total amount and the extension of precipitation zone, with the objective to provide new corrective measures based on permeability reduction. For instance, one can isolate a target aquifer region hydraulically by creating an impervious barrier in the mixing zone. Laboratory experiments were used to study the effect of chaotic advection on mixing-induced precipitation. The experiments were performed in a transparent horizontal two-dimensional tank made of plexiglass filled with glass beads. In the experimental investigation, two different chemical solutions containing CaCl and NaCO3 were injected in separate inlet ports with different concentration. oscillatory flow was created by tuning the inflow rate, we analyze the effect of different injection rates on precipitation. As a result, a calcite precipitate layer with different width was formed between the individual solutions. Color tracer tests were injected before and after the experiment to visualize the impact of precipitation.

How to cite: Gonzalez-Subiabre, G., Fernàndez-Garcia, D., Trabucchi, M., and Carrera, J.: Effect of chaotic advection generated by oscillatory flow on mixing-induced precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5191, https://doi.org/10.5194/egusphere-egu22-5191, 2022.

The understanding of the dynamics of reaction diffusion (RD) fronts is crucial for a wide variety of applications in chemistry, biology, physics and ecology, and it is especially important for hydrogeological problems involving chemical reactions. Reactive transport in geological media is generally controlled by the interplay of physical and chemical processes, which can give rise to complex dynamics of the reaction front. An important subset of RD fronts is represented by autocatalytic fronts, for which it is well known that the coupling of diffusion and chemical processes gives rise to self-organization phenomena and pattern forming instabilities [1]. When the initial interface between the reactant and the catalyst is a straight line, the autocatalytic front behaves as a solitary wave, which means that the shape of the front remains unchanged as it travels towards the nonreacted species [2]. The coupling with uniform advection does not change the picture, provided that the system is described in the proper comoving reference frame.

However, in this work we show that the geometrical properties of the injection source have a significant impact on the reaction front dynamics. Indeed, if the injection of one reactant into the other is performed radially at a constant flow rate, the pre-asymptotic dynamics of the front is strongly affected by the nonuniform velocity field. Moreover, although at long times the front still behaves as a solitary wave, the efficiency of the reaction is strongly increased in virtue of the increasing volume occupied by the radial front. We show how injecting a finite amount of reactant into the catalyst gives rise to collapsing fronts and we characterize their dynamics in terms of their position, width and the production rate. In contrast, when the reactant is injected into the catalyst at a constant flow rate, a stationary regime is reached where, unlike the case of solitary waves, the autocatalytic front does not move.      

References:

[1] I. R. Epstein and J. A. Pojman, An Introduction to Nonlinear Dynamics: Oscillations, Waves, Patterns, and Chaos (Oxford University Press, Oxford, 1998)

[2] P. Gray, K. Showalter, and S. K. Scott, J. Chim. Phys. 84, 1329 (1987)

How to cite: Comolli, A., Brau, F., and De Wit, A.: Effect of radial geometry on autocatalytic reaction-diffusion-advection fronts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5286, https://doi.org/10.5194/egusphere-egu22-5286, 2022.

The kinetic interface-sensitive (KIS) tracer, relying on a zero-order reaction on the fluid-fluid interface, is a newly developed method to measure the fluid-fluid interfacial area (FIFA) in drainage processes. The concentration of the reaction product, obtained by measuring the water samples after the breakthrough, is interpolated with numerical model to determine the FIFA. However, a major limitation of the previous method is that the volume of available water sample is highly dependent on the sand type and the system parameters, and the measurement is not applicable when the water sample is not sufficient. An alternative is to apply the KIS tracer in the “push-pull” test, meaning the drainage process is followed by an imbibition process with the flow direction reversed. This study applies the pore-scale numerical simulation and the column experiment to study the KIS tracer reactive transport during a push-pull test. The breakthrough curve of the product concentration is interpolated with both macro-scale numerical model and a modified analytical solution for the push-pull process. It is found the shapes of the concentration breakthrough curves from the pore-scale simulations and the column experiments are fit, showing a non-linear descending trend with respect to time. The KIS tracer reactive transport process in the push-pull test and the validation of the measured FIFA from the concentration breakthrough curve, are demonstrated based on the pore-scale simulation results. Finally, for the (n-octane/water) displacement process in the column packed with the glass beads with diameter of 240 μm (at the capillary number of 5×10^-7), the FIFA is measured 210 m^-1 at the water saturation of 0.33, which is consistent with some literature data.

How to cite: Gao, H., Tatomir, A., Abdullah, H., and Sauter, M.: A push-pull kinetic interface-sensitive tracer method to quantify the fluid-fluid interfacial area in dynamic two-phase flow in porous media, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6606, https://doi.org/10.5194/egusphere-egu22-6606, 2022.

The process of mineral precipitation and crystal growth begins with nucleation, which is usually overlooked in reactive transport simulators. Nucleation controls the location and timing of solid mineral formation in porous media. For an accurate prediction of the hydrodynamics of the porous medium after mineral precipitation, it is crucial to know the spatial distribution of stable secondary nuclei. We developed a novel probabilistic nucleation approach wherein induction time is treated as a random variable in order to better understand the nucleation process. The probabilistic induction time statistically spreads around the measured or reported induction time, either obtained from experiments or approximated by the exponential nucleation rate equation suggested by the classical nucleation theory (CNT). In this study, we used the classical nucleation theory. The location and time of nucleation are both probabilistic in our model, affecting transport properties at different time and length scales.

We developed a pore-scale Lattice Boltzmann reactive transport model incorporated with the new probabilistic nucleation model to investigate the effect of nucleation rate and reaction rate on the extent, distribution, and precipitation pattern of the solid phases. The simulation domain is a 2D substrate with an infinite source of the supersaturated solution. We use Shannon entropy to measure the disorder of the spatial mineral distributions. The results of the simulations show that all the reactions follow similar random behavior with different Gauss-Laplace distributions. The simulation scenarios start from a fully ordered system with no solid precipitation on the substrate (entropy of 0). Entropy starts to increase as the secondary phase precipitates and grows on the surface until it reaches its maximum value (entropy of 1). Afterward, the overall disorder declines as more surface areas are being covered, and eventually, entropy approaches a constant value. The results indicate that the slower reactions have longer windows of the probabilistic regime before entering the deterministic regime. The outcomes provide the basis for implementing mineral nucleation and growth for reactive transport modeling across time-scales and length-scales.

How to cite: Masoudi, M., Nooraiepour, M., and Hellevang, H.: On the effect of probabilistic nucleation on the distribution of mineral precipitates in porous media, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8398, https://doi.org/10.5194/egusphere-egu22-8398, 2022.

Interfacial fluid instabilities are ubiquitous in Nature and are responsible for many important phenomena. In some cases, they play a constructive role like in the redistribution of energy in a system but, in some other cases, the role is destructive and may pose a serious threat to technical or industrial applications. In most cases, these fluids involve reactants that are known to modify the instability itself.

Fingering instabilities are special cases of fluid instabilities that occur when a high mobility fluid displaces a low mobility one [1]. Processes like enhanced oil recovery or other fluid displacements in porous media, such as chromatography, are examples in which the existence of fingering instability is crucial for the overall extraction performance. At a laboratory scale, these instabilities are studied in experimental arrangements known as Hele-Shaw cells. A particularity of these cells is that the flow inside them is representative of the flow in porous media.

In this work, we propose a chemical system likely to produce instabilities. We endow it with the appropriate chemical reactions at the interface that make it possible to control the activation or deactivation of the fingering instability at will. In particular, we consider two different fluids with different viscosities and analyze the displacement of one fluid by the other injected into a radial Hele-Shaw cell. We studied two different scenarios depending on which fluid is used as displacing/displaced solution [2].

In the first case, where the most viscous fluid displaces the less viscous one (initially stable configuration), pattern formation is observed when the characteristic flow and reactive timescales are similar. The patterns show complex dynamics in which fingers not only grow but move forward/backward. In the second case (initially unstable configuration), the unfavorable mobility ratio produces complex wormhole structures similar to those observed in dissolving rock fractures [3,4]. The displacement stabilizes when flow, diffusive, and reactive timescales are comparable.

We extensively characterized and numerically modeled both scenarios. Our results establish the basis to control fluid instabilities that may arise in a broad variety of contexts.  

REFERENCES:

[1] Homsy, G. M. (1987). Viscous fingering in porous media. Annual review of fluid mechanics, 19(1), 271-311.

[2] Escala, D. M., & Muñuzuri, A. P. (2021). A bottom-up approach to construct or deconstruct a fluid instability. Scientific reports, 11(1), 1-16.

[3] Szymczak, P., & Ladd, A. J. C. (2009). Wormhole formation in dissolving fractures. Journal of Geophysical Research: Solid Earth, 114(B6).

[4] Kalia, N., & Balakotaiah, V. (2007). Modeling and analysis of wormhole formation in reactive dissolution of carbonate rocks. Chemical Engineering Science, 62(4), 919-928.

How to cite: Escala, D. M. and Pérez Muñuzuri, A.: Complex Pattern Formation and Viscous Fingering Stabilization in Radial Flow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10079, https://doi.org/10.5194/egusphere-egu22-10079, 2022.

The kinetic interface sensitive (KIS) tracers have been the focus of research in the past decade, as a new, reactive tracer method to estimate the interfacial area between immiscible fluids in porous media. We present here a novel experimental approach to measure the capillary associated fluid-fluid interfacial area using the KIS tracers in simultaneous two-phase flow conditions. The new approach is applied in a sand column filled with glass-beads (d₅₀ = 170µm). Four laboratory experiments are performed in a simultaneous two-phase injection scheme using different fractional flow ratios (Flow rate of wetting phase: total flow rate). The different fractional ratios create different saturations inside the column, which correlate to different fluid-fluid interfacial areas. The new method, introduces also a new analytical method to handle reacted by-product concentration data acquired, different from the KIS tracer method in dynamic conditions. By comparing the results to other established techniques reported in the literature (i.e., interfacial partitioning tracer test and computed micro-tomography) used to measure fluid-fluid interfacial area we observe a good agreement.  The capillary associated interfacial area increases with decreasing wetting saturation until a maximum value, which then drops near the residual saturation. The maximum capillary associated interfacial area occurs at wetting saturation ranges between 0.45 < S_w < 0.6, which is slightly shifted towards the higher wetting saturation when compared to the other techniques. Furthermore, the results are simulated using a Darcy-scale reactive transport multiphase flow in porous media numerical model.

How to cite: Abdullah, H., Tatomir, A., and Sauter, M.: Experimental approach to measure capillary associated interfacial area using kinetic interface sensitive tracers in a simultaneous two-phase flow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11132, https://doi.org/10.5194/egusphere-egu22-11132, 2022.

Convective dissolution is the process by which CO₂ injected in geological formations dissolves into the aqueous phase and thus remains stored perennially by gravity. It can be modeled by buoyancy-coupled Darcy flow and solute transport. The transport equation should include a diffusive term accounting for hydrodynamic dispersion, wherein the effective diffusion coefficient is proportional to the local interstitial velocity. We investigate the impact of the hydrodynamic dispersion tensor on convective dissolution in two-dimensional (2D) and three-dimensional (3D) homogeneous porous media. Using a novel numerical model we systematically analyze, among other observables, the time evolution of the fingers’ structure, dissolution flux in the quasi-constant flux regime, and mean concentration of the dissolved CO₂; we also determine the onset time of convection, t_on. For a given Rayleigh number Ra, the efficiency of convective dissolution over long times is controlled by t_on. For porous media with a dispersion anisotropy commonly found in the subsurface, t_on increases as a function of the longitudinal dispersion’s strength (S), in agreement with previous experimental findings and in contrast to previous numerical findings, a discrepancy which we explain. More generally, for a given strength of transverse dispersion, longitudinal dispersion always slows down convective dissolution, while for a given strength of longitudinal dispersion, transverse dispersion always accelerates it. Furthermore, systematic comparison between 2D and 3D results shows that they are consistent on all accounts, except for a slight difference in t_on and a significant impact of Ra on the dependence of the finger number density on S in 3D.

How to cite: Méheust, Y., Dhar, J., Meunier, P., and Nadal, F.: Convective dissolution of Carbon Dioxide in two- and three-dimensional porous media: the impact of hydrodynamic dispersion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13563, https://doi.org/10.5194/egusphere-egu22-13563, 2022.

The reduction of carbon dioxide concentration in the atmosphere has become an important objective to diminish the predicted exponential increase in global temperatures. A promising long-term solution is carbon capture, and sequestration (CCS), whereby CO₂ is injected into saline aquifers containing high concentrations of divalent cations leading to the mineralization of carbonate salts. These precipitation reactions provide a potential long-term solution for storing and preventing reentry of this greenhouse gas into the atmosphere. Our study aims to understand the influence of the initial host solution composition on CCS. Using two glass plates separated by a thin gap (~1 mm), we steadily inject CO₂ gas above an alkaline aqueous solution of either calcium chloride and/or magnesium chloride and monitor the convective uptake of CO₂ and subsequent mineralization into calcium carbonate (e.g., calcite, aragonite, and vaterite), magnesium carbonate (e.g., hydromagnesite), or calcium magnesium carbonate (e.g., dolomite). The buoyancy-driven convective dynamics from the dissolution of CO₂ is monitored using schlieren imaging techniques. In addition, a pH indicator in the initial metal salt solution shows its acidification from the continuous uptake of CO₂. The mineral products are analyzed using X-ray diffraction, Raman spectroscopy and scanning electron microscopy to determine the composition, crystal structure, and crystal habit.

How to cite: Knoll, P. and De Wit, A.: The Effect of Calcium and Magnesium Ions on CO2 Convective Dissolution and Carbonate Precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13570, https://doi.org/10.5194/egusphere-egu22-13570, 2022.