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Using high-resolution micro-CT imaging at 2.98 μm/voxel, we compared the percolation of hydrogen in gas injection with gas expansion for a hydrogen-brine system in Bentheimer sandstone at 1 MPa and 20 °C, representing hydrogen storage in an aquifer. We introduced dimensionless numbers to quantify the contribution of advection and expansion to displacement. We analysed the 3D spatial distribution of gas and its displacement in both cases and demonstrated that in gas injection, hydrogen can only advance from a connected cluster in an invasion-percolation type process, while in gas expansion, hydrogen can access more of the pore space even from disconnected clusters. The average gas saturation in the sample increased from 30% to 50% by gas expansion, and we estimated that 10% of the expanded volume is attributed to hydrogen exsolution from the brine. This work emphasises the importance of studying the combined effects of pressure decline and gas withdrawal in hydrogen storage to assess the influence of gas expansion on remobilising trapped gases. [Display omitted] • High-resolution X-ray imaging studied hydrogen injection and expansion in a sandstone. • Disconnected gas clusters can expand and reconnect during pressure decline. • Gas expansion increased the average gas saturation from 30% to 50% as pressure declined. • Hydrogen exsolution from brine increased the expanded gas volume by 10%. • Hydrogen accessed more of the larger pores by expansion than by injection. [ABSTRACT FROM AUTHOR]

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random distribution functions. We developed a mathematical model of gas–water two-phase flow based on the Navier–Stokes equation. The gas-driven water processes in porous media were described using the level-set method and solved through the finite element method. We investigated the effects of the nonhomogeneous structure of pore media, wettability, and repulsion rate on gas-driven water channeling. The nonhomogeneity of the pore medium is the most critical factor influencing the flow. The size of the throat within the hydrophilic environment determines the level of difficulty of gas-driven water flow. In regions with a high concentration of narrow passages, the formation of extensive air-locked areas is more likely, leading to a decrease in the efficiency of the flow channel. In the gas–water drive process, water saturation changes over time according to a negative exponential function relationship. The more hydrophilic the pore medium, the more difficult the gas-phase drive becomes, and this correlation is particularly noticeable at higher drive rates. The significant pressure differentials caused by the high drive-off velocities lead to quicker methane breakthroughs. Instantaneous flow rates at narrow throats can be up to two orders of magnitude higher than average. Additionally, there is a susceptibility to vortex flow in the area where the throat connects to the orifice. The results of this study can enhance our understanding of gas–water two-phase flow in porous media and help commercialize the exploitation of clean energy in the deep ocean. [ABSTRACT FROM AUTHOR]

This study extensively investigates the influence of different pyrolysis temperatures and organic matter contents on the fluid flow and heat transfer properties in oil shale samples. Utilizing CT images to generate three-dimensional digital rock, coupled simulations of CO 2 flow and heat transfer were conducted, analyzing parameters such as velocity fields, permeability, temperature fields, average temperatures, and heat transfer coefficients. The results reveal that, for relatively homogeneous oil shale samples, the permeability exhibits a monotonous increase with rising pyrolysis temperature. While the effect of pyrolysis temperature on the distribution characteristics of velocity and temperature fields is minimal, it significantly impacts the heat transfer coefficients. Specifically, the heat transfer coefficients increase significantly in the direction perpendicular to the bedding plane, while they decrease or remain unchanged parallel to it. Additionally, the organic matter content significantly influences the fluid flow and heat transfer properties of shale samples. After undergoing heat treatment, the heterogeneity of pore structures in shale samples varies significantly, affecting the characteristics of fluid flow and heat transfer. The influence of organic matter content and pyrolysis temperature on fluid flow and heat transfer in shale primarily stems from the effect of organic matter pyrolysis on the original pore structure. The development and connectivity of pore networks are closely related to the distribution characteristics of the original organic matter and are not directly correlated with the organic matter content. These findings provide essential theoretical guidance and technical support for the development and utilization of oil shale resources, while also offering valuable references and insights for future research. [ABSTRACT FROM AUTHOR]

Micro‐continuum models are versatile and powerful approaches for simulating coupled processes in two‐scale porous systems. Initially oriented for modeling static single‐phase flow in microtomography images with sub‐voxel porosity, the concept has been extended over the years to multi‐phase flow, reactive transport, and poromechanics. This paper introduces an integrated micro‐continuum framework to model coupled processes in porous media. It reviews state‐of‐the‐art models and discusses applications in geosciences including Digital Rock Physics with sub‐voxel porosity, moving fluid‐solid interface at the pore‐scale due to geochemical reactions, fracture‐matrix interactions, and solid deformation. Finally, the paper discusses future developments in micro‐continuum models. Key Points: Micro‐continuum models are hybrid‐scale approaches for solving flow and transport in porous mediaState of the art micro‐continuum models handle full Temperature‐Hydrodynamics‐Mechanics‐Chemistry coupling in unsaturated environmentsApplications include Digital Rock Physics with sub‐voxel porosity, pore‐scale reactive transport, and poromechanics [ABSTRACT FROM AUTHOR]

The core pore structure of the target shale oil block was finely characterized using scanning electron microscopy， and a microscopic numerical model of the pore-scale core was constructed to elucidate the intrinsic mechanisms and the main controlling factors of spontaneous imbibition of fracturing fluid within the complex pore space of shale. On this basis， research was conducted on spontaneous imbibition within the fracture-matrix system. The Navier-Stokes （N-S） equations were coupled with the level-set method to track changes in the oil and water interface， thus clarifying the oil and water two-phase flow characteristics and evaluating the efficiency of spontaneous imbibition under the influence of the wettability， viscosity ratio of oil and water， and interfacial tension. The research results revealed that large and small intercommunicating pores in shale form intricate microscopic displacement units under capillary action. When the rock wettability presents a water-wet state， water preferentially infiltrates from the fracture into the smaller pores， expelling oil from larger pores into the fracture， and the produced range of crude oil within the matrix pores is wider， resulting in higher spontaneous imbibition efficiency. When the rock wettability turns oil-wet， crude oil within the small pores cannot be produced during spontaneous imbibition， while the water invades from larger pores， causing crude oil to be displaced from other large pores. This results in a lower spontaneous imbibition efficiency and a small range of crude oil produced in the matrix pores. The spontaneous imbibition in the initial phase is faster but gradually slows over time. Stronger water wettability of shale indicates a lower viscosity ratio of oil and water and higher interfacial tension， resulting in a wider range of crude oil produced within the matrix pores and a cumulative efficiency of spontaneous imbibition of more than 15%.

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random distribution functions. We developed a mathematical model of gas–water two-phase flow based on the Navier–Stokes equation. The gas-driven water processes in porous media were described using the level-set method and solved through the finite element method. We investigated the effects of the nonhomogeneous structure of pore media, wettability, and repulsion rate on gas-driven water channeling. The nonhomogeneity of the pore medium is the most critical factor influencing the flow. The size of the throat within the hydrophilic environment determines the level of difficulty of gas-driven water flow. In regions with a high concentration of narrow passages, the formation of extensive air-locked areas is more likely, leading to a decrease in the efficiency of the flow channel. In the gas–water drive process, water saturation changes over time according to a negative exponential function relationship. The more hydrophilic the pore medium, the more difficult the gas-phase drive becomes, and this correlation is particularly noticeable at higher drive rates. The significant pressure differentials caused by the high drive-off velocities lead to quicker methane breakthroughs. Instantaneous flow rates at narrow throats can be up to two orders of magnitude higher than average. Additionally, there is a susceptibility to vortex flow in the area where the throat connects to the orifice. The results of this study can enhance our understanding of gas–water two-phase flow in porous media and help commercialize the exploitation of clean energy in the deep ocean.

Summary: The effect of root hairs on water uptake remains controversial. In particular, the key root hair and soil parameters that determine their importance have been elusive.We grew maize plants (Zea mays) in microcosms and scanned them using synchrotron‐based X‐ray computed microtomography. By means of image‐based modelling, we investigated the parameters determining the effectiveness of root hairs in root water uptake. We explicitly accounted for rhizosphere features (e.g. root–soil contact and pore structure) and took root hair shrinkage of dehydrated root hairs into consideration.Our model suggests that > 85% of the variance in root water uptake is explained by the hair‐induced increase in root–soil contact. In dry soil conditions, root hair shrinkage reduces the impact of hairs substantially.We conclude that the effectiveness of root hairs on root water uptake is determined by the hair‐induced increase in root–soil contact and root hair shrinkage. Although the latter clearly reduces the effect of hairs on water uptake, our model still indicated facilitation of water uptake by root hairs at soil matric potentials from −1 to −0.1 MPa. Our findings provide new avenues towards a mechanistic understanding of the role of root hairs on water uptake. See also the Commentary on this article by Boursiac & Bauget 240: 2173–2175. [ABSTRACT FROM AUTHOR]

An investigation of one-temperature or two-temperature models in numerical simulations of the melting process of a phase change material is presented in this work. In this study, Kelvin cell was used to simulate a case in the pore scale and the results were compared with experimental values. For the first time that a real experiment in large dimensions is simulated at the pore scale. The problem was simulated based on the one-temperature porous model. It was shown that the one-temperature porous model compares well with the results of the pore-scale simulation. Furthermore, the two-temperature model is not required for these types of studies. Results for different models were compared carefully and the reasons for the discrepancy between results were explained. [ABSTRACT FROM AUTHOR]

The success of foam to reduce CO2 mobility in CO2 enhanced oil recovery and CO2 storage operations depends on foam stability in the reservoir. Foams are thermodynamically unstable, and factors such as surfactant adsorption, the presence of oil, and harsh reservoir conditions can cause the foam to destabilize. Pore-level foam coarsening and anti-coarsening mechanisms are not, however, fully understood and characterized at reservoir pressure. Using lab-on-a-chip technology, we probe dense (liquid) phase CO2 foam stability and the impact of Ostwald ripening at 100 bars using dynamic pore-scale observations. Three types of pore-level coarsening were observed: (1) large bubbles growing at the expense of small bubbles, at high aqueous phase saturations, unrestricted by the grains; (2) large bubbles growing at the expense of small bubbles, at low aqueous phase saturation, restricted by the grains; and (3) equilibration of plateau borders. Type 3 coarsening led to stable CO2 foam states eight times faster than type 2 and ten times faster than type 1. Anti-coarsening where CO2 diffused from a large bubble to a small bubble was also observed. The experimental results also compared stabilities of CO2 foam generated with hybrid nanoparticle–surfactant solution to CO2 foam stabilized by only surfactant or nanoparticles. Doubling the surfactant concentration from 2500 to 5000 ppm and adding 1500 ppm of nanoparticles to the 2500 ppm surfactant-based solution resulted in stronger foam, which resisted Ostwald ripening. Dynamic pore-scale observations of dense phase CO2 foam revealed gas diffusion from small, high-curvature bubbles to large, low-curvature bubbles and that the overall curvature of the bubbles decreased with time. Overall, this study provides in situ quantification of CO2 foam strength and stability dynamics at high-pressure conditions. Article Highlights A comprehensive laboratory investigation of CO2 foam stability and the impact of Ostwald ripening. Pore-level foam coarsening and anti-coarsening mechanisms insights. [ABSTRACT FROM AUTHOR]

Carbonate gas reservoirs with edge and bottom water contain abundant reserves, making them key production targets in the Tarim Basin, Sichuan Basin, Ordos Basin, and other petroleum provinces. Water invasion may occur in the middle and late development stages of such reservoirs, leading to reduction of gas displacement efficiency and gas recovery. In this paper, a pore-scale water-gas immiscible flow model is established by coupling the fluid flow equation and the gas-water contact (GWC) tracking equation. The process of gas displacement with water is simulated in the heterogeneous porous media generated by the quartet structure generation set (QSGS). Finally, the mechanisms of remaining gas distribution and formation are analyzed, and the variation mechanism of microscopic gas displacement efficiency is discussed. The results are obtained in three aspects. First, the remaining gas is distributed at the blind end, in the pore-throat and as clusters, with their proportions and scales jointly controlled by microscopic pore structures, wettability and capillary number. The remaining gas can be further produced by changing the production pressure differential to disturb the original pressure system and gas expansion, so as to improve the microscopic gas displacement efficiency. Second, the microscopic gas displacement efficiency is closely related to the gas flow process. Formation or expansion of each water flow path may cause rapid increase of water cut and slows down the increase of gas displacement efficiency. Third, the microscopic pore structure and wettability are the inherent features of the gas reservoir, so the capillary number can be optimized to change the mode of GWC advancement, and then to effectively improve the microscopic gas displacement efficiency. It is concluded that for real gas wells, the evolution of mechanical mechanisms of GWC advancement should be revealed depending upon the microscopic pore structure and wettability of the reservoir, and then the optimal capillary number can be determined. Furthermore, clarifying the pore-scale water-gas flow characteristics and physical mechanism of microscopic gas displacement provides guidance for the planning of enhanced gas recovery.

In various natural and engineered systems, mineral–fluid interactions take place in the presence of multiple fluid phases. While there is evidence that the interplay between multiphase flow processes and reactions controls the evolution of these systems, investigation of the dynamics that shape this interplay at the pore scale has received little attention. Specifically, continuum scale models rarely consider the effect of multiphase flow parameters on mineral reaction rates or apply simple corrections as a function of the reactive surface area or saturation of the aqueous phase, without developing a mechanistic understanding of the pore-scale dynamics. In this study, we developed a framework that couples the two-phase flow simulator of OpenFOAM (open field operation and manipulation) with the geochemical reaction capability of CrunchTope to examine pore-scale dynamics of two phase flow and their impacts on mineral reaction rates. For our investigations, flat 2D channels and single sine wave channels were used to represent smooth and rough geometries. Calcite dissolution in these channels was quantified with single phase flow and two phase flow at a range of velocities. We observed that the bulk calcite dissolution rates were not only affected by the loss of reactive surface area as it becomes occupied by the non-reactive non-aqueous phase, but also largely influenced by the changes in local velocity profiles, e.g., recirculation zones, due to the presence of the non-aqueous phase. The extent of the changes in reaction rates in the two-phase systems compared to the corresponding single phase system is dependent on the flow rate (i.e., capillary number) and channel geometry, and follows a non-monotonic relationship with respect to aqueous saturation. The pore-scale simulation results highlight the importance of interfacial dynamics in controlling mineral reactions and can be used to better constrain reaction rate descriptions in multiphase continuum scale models. These results also emphasize the need for experimental studies that underpin the development of mechanistic models for multiphase flow in reactive systems.

Ostwald ripening of gas bubbles is a spontaneous mass transfer process that can impact the storage volume of trapped gas in the subsurface. In homogeneous porous media with identical pores, bubbles evolve toward an equilibrium state of equal pressure and volume. How the presence of two liquids impacts ripening of a bubble population is less known. We hypothesize that the equilibrium bubble sizes depend on the surrounding liquid configuration and oil/water capillary pressure. We investigate ripening of nitrogen bubbles in homogeneous porous media containing decane and water using a level set method that alternately simulates capillary-controlled displacement and mass transfer between bubbles to eradicate chemical-potential differences. We explore impacts of initial fluid distribution and oil/water capillary pressure on the bubble evolution. Ripening in three-phase scenarios in porous media stabilizes gas bubbles to sizes that depend on their surrounding liquids. Bubbles in oil decrease in size while bubbles in water increase in size with increasing oil/water capillary pressure. Bubbles in oil reach local equilibrium before the three-phase system stabilizes globally. A potential implication for field-scale gas storage is that the trapped gas fractions in oil and water vary with depth in the oil/water transition zone. • Level set approach to gas bubble ripening on three-phase fluid configurations in porous media. • Equilibrium bubble sizes in oil and water depend on oil/water capillary pressure and gas/liquid interfacial tensions. • Ripening of gas bubbles in three-phase fluid systems displays a different behaviour in porous media than in bulk liquids. • Oil/water capillary pressure impacts the equilibration time for three-phase ripening scenarios in porous media. [ABSTRACT FROM AUTHOR]

This study presents a pore-scale model of a complex homogeneous-heterogeneous reaction. It is based on the Stokes equations, convection-diffusion-reaction equations, and Robin boundary conditions. The fluid is considered non-Newtonian, and the Carreau model of viscosity is employed. A heterogeneous reaction is defined by the Langmuir isotherm, whereas a homogeneous reaction is described by cubic autocatalysis over the entire pore space. The finite element method is used for space discretization, namely, Taylor–Hood elements ( – ) for hydrodynamic processes and Lagrange polynomials of the first degree () for reactive transport. The Crank–Nicholson scheme is used for time discretization. Newton's iterative method is implemented to solve a non-linear problem for reactive mass transport and Picard iterations for non-Newtonian fluid flow. The fluid flow influences the species transport, but there is no backward influence of the species concentration on the fluid flow. The influence of the power law parameter of the Carreau model for viscosity on the reacting processes is verified. The dimensionless form of equations was used throughout the entire numerical analysis in this paper. The numerical results show that the fluid flow parameters slightly affect the breakthrough curves, specifically for the catalyst. [ABSTRACT FROM AUTHOR]

Select porous carbonate cores are used to carry out water-flooding oil micro-CT flooding experiments, and use image processing to separate oil, water, microfacies, and rock skeleton. The gray value is used to determine the distribution position of the microfacies sub-resolution remaining oil. The gray image resolution is improved by the SRCNN method to improve the pore identification accuracy. The distribution and evolution law of the sub-resolution remaining oil after the displacement is determined by the oil-water distribution results. Using the SRCNN method, the pore recognition accuracy of the original scanned images of the two samples was increased by 47.88 times and 9.09 times, respectively. The sub-resolution residual oil and the macro-pore residual oil were determined from the CT scan images after the brine was saturated and divided into five categories. With the increase in the displacement ratio, the columnar and droplet residual oil of the low-permeability samples first increased and then decreased, and the cluster residual oil gradually decreased. The continuous residual oil of the hypertonic samples gradually decreased, and the discontinuous residual oil gradually increased. According to the research results of carbonate pore throat identification and sub-resolution microscopic residual oil change characteristics after water flooding under the SRCNN method, a method for distinguishing porous carbonate reservoirs is provided. [ABSTRACT FROM AUTHOR]

Liquid nitrogen (LN2) is of great potential in stimulating reservoirs. Thanks to the low viscosity and ultralow temperature, which makes it easy to penetrate rock pores and intensified rock failure. However, the flow and heat transfer characteristics of LN2 in rock pores are still not well understood, which limits the development of LN2 fracturing technology. To address this issue, a flow and heat transfer model was established based on Lattice Boltzmann Method (LBM). A connectivity sandstone pore model was presented, combining CT scanning and the improved connectivity algorithm proposed in this paper. A series of simulations were conducted to investigate how the existence of pores and the fluid flow affect heat transfer. Moreover, a pore-scale Lattice Boltzmann Method (LBM) simulation optimization method was proposed to improve the calculation efficiency. The results indicate that the existence of pores and fluid flow will inhibit and assist the heat transfer, respectively. Besides, the effect of pore itself on heat transfer is greater than that of pore flow. Meanwhile, the flow and heat transfer of LN2 and two other common fracturing fluids were compared. Under the same condition, the velocity of LN2 and its rate of cooling rock are the greatest, followed by supercritical carbon dioxide (SC-CO2) and water. As a kind of fracturing fluid, LN2 is better than the other two fluids in terms of flow and heat transfer characteristics. This study provides an in-depth understanding of the mechanism of heat transfer between rocks and LN2. [ABSTRACT FROM AUTHOR]

Fluid flow through porous material is relevant in different fields of engineering, such as in engine and vehicle development, and can be supported through CFD simulation. Numerical simulations at the pore-scale can be used to replace or reduce expensive laboratory measurements. These methods offer a valuable opportunity to connect the pore-scale properties of the porous material with displacement processes on the continuum-scale. Furthermore, they allow researchers to specify crucial flow properties, e.g., capillary pressure, which are crucial for REV-scale research. Three main methods, direct numerical, pore network modeling, and hybrid approaches, are widely used in order to analyze the pore-scale mechanics of fluid flow behavior through porous materials with CFD simulations. The present comprehensive review demonstrates and highlights the significant advantages, disadvantages, and critical challenges in the pore-scale fluid flow simulations. The main challenges include the characterization of material properties, and up-scaling process from pore to continuum or field-scale. [ABSTRACT FROM AUTHOR]

Water in municipal sludge has an electric double layer (EDL), and can be rapidly removed via electroosmosis. However, the understanding of the physical mechanisms of electroosmosis is limited owing to the complex pore structure of sludge porous media, which may restrict the development of electric dewatering (EDW) technology. In this study, the sludge microstructure was measured using the computerized tomography technique and quantitatively characterized using fractal geometry. A new pore-scale physical model for the electroosmotic flow through sludge porous media was developed based on the EDL theory, and the analytical expressions for the electroosmotic flow rate and permeability coefficient were determined. The proposed fractal pore-scale model for electroosmotic flow was validated by comparing it with the measured electroosmotic flow rate using a self-designed EDW device for municipal sludge composed of a hydraulic system and applied electric field. The results show that the electroosmotic flow rate of sludge porous media depends not only on the applied electric field, but also on the sludge microstructure including porosity, maximum pore size, and pore and tortuosity fractal dimensions. However, the correlation between the electroosmotic flow rate and the voltage gradient was usually nonlinear, and became linear only if the tortuosity fractal dimension equaled to one (straight flow path). The electroosmotic permeability coefficient increases with an increase in porosity; however, it is lowered by the increased pore and tortuosity fractal dimensions under a certain porosity. The electroosmosis phenomenon can effectively remove part of the interstitial water and surface water in sludge porous media, and the proposed electroosmotic physical model provides a useful theoretical basis for the development of EDW technology for municipal sludge. [ABSTRACT FROM AUTHOR]

The understanding of multiphase flow phenomena occurring in porous media at the pore scale is fundamental in a significant number of fields, from life science to geo and environmental engineering. However, because of the optical opacity and the geometrical complexity of natural porous media, detailed visual characterization is not possible or is limited and requires powerful and expensive imaging techniques. As a consequence, the understanding of micro-scale behavior is based on the interpretation of macro-scale parameters and indirect measurements. Microfluidic devices are transparent and synthetic tools that reproduce the porous network on a 2D plane, enabling the direct visualization of the fluid dynamics. Moreover, microfluidic patterns (also called micromodels) can be specifically designed according to research interests by tuning their geometrical features and surface properties. In this work we design, fabricate and test two different micromodels for the visualization and analysis of the gas-brine fluid flow, occurring during gas injection and withdrawal in underground storage systems. In particular, we compare two different designs: a regular grid and a real rock-like pattern reconstructed from a thin section of a sample of Hostun rock. We characterize the two media in terms of porosity, tortuosity and pore size distribution using the A* algorithm and CFD simulation. We fabricate PDMS-glass devices via soft lithography, and we perform preliminary air-water displacement tests at different capillary numbers to observe the impact of the design on the fluid dynamics. This preliminary work serves as a validation of design and fabrication procedures and opens the way to further investigations. [ABSTRACT FROM AUTHOR]

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• Novel simulation method explores diffusion in bi-dispersed pores. • Study critiques Maxwell and Nield models' predictivity limits. • Modifies random pore model, boosts accuracy in low macro-porosity. The classical diffusion models fail to predict the diffusivity of bi-dispersed porous materials, particularly at low macro-porosity. In this work, a pore-scale simulation is carried out to investigate the diffusion process inside ordered and random bi-dispersed pore structures under different growth phases and shapes. The applicability of existing models is evaluated. The results reveal that Maxwell and Nield models are inadequate to predict the diffusivity of the ordered macropore structure under different growth phase types and shapes. Meanwhile, the ordered distribution of microporous spherical particles is superior to that of macropores. For random pore structure, the macropore-macropore diffusion path contributes to the error of the random pore model, which depends on the ratio of the micropore-macropore diffusivity. [ABSTRACT FROM AUTHOR]

• A 3D model of multiphase reactive flow with solid dissolution is proposed. • The diagram of multiphase reactive flow including several patterns is established. • A new correlation of reactive surface area-porosity-saturation is formulated. • Different pore size distributions and bubble characteristics are quantified. • The mass transfer coefficient and effective reaction rate are evaluated. There are still many unclear mechanisms in the multiphase reactive flow with solid dissolution processes. In this study, the reactive transport processes coupled with solid dissolution and self-induced multiphase flow in three-dimensional (3D) structures with increasing complexity is studied by developing a 3D computational microfluidic method, which considers multiphase flow, interfacial mass transport, heterogeneous chemical reactions, and solid structure evolution. Solid dissolution diagram in a simple channel in the framework of multiphase flow is proposed, with six coupled multiphase flow and solid dissolution patterns identified and the transition between different patterns discussed. Then, multiphase reactive flow in a porous chip is further studied, and the interesting 3D phenomena are discovered, including enhanced solid dissolution in the middle and enriched bubble generation at the corner along the thickness direction. Considering the importance of reactive surface area, correlations of reactive surface area-porosity-saturation with different dissolution patterns are proposed based on the pore-scale results. Finally, the computational microfluidic model is extended to investigate the multiphase reactive flow in a 3D digital core. Different dissolution patterns are recognized using the local porosity evolution character, and the corresponding pore size distribution and bubble characteristics are deciphered. These findings advance understanding of multiphase reactive transport processes and contribute to improve continuum-scale reactive transport modeling. Computational microfluidic study of multiphase reactive flow with solid dissolution and bubble generation in a simple channel, a microfluidic porous chip, and a digital core. [Display omitted] [ABSTRACT FROM AUTHOR]

The phase equilibrium conditions of methane hydrate, particularly the phase equilibrium pressure, are influenced by capillary pressure. In this study, the existing model for phase equilibrium pressure is enhanced, and a novel methane hydrate dissociation model is formulated by integrating it with the established hydrate dissociation model. A numerical simulation is conducted on experimental research, and the reliability of the model is validated through comparison with experimental data, yielding consistent results. The significance and necessity of considering capillary pressure between hydrate and water in the exploration of methane hydrate dissociation in micropores are elucidated. The proposed model is employed to further elucidate the evolution of various factors such as methane generation rate, phase distribution, temperature distribution, and phase equilibrium pressure distribution. The findings underscore the critical role of capillary pressure between hydrates and water, emphasizing its substantial impact on the accuracy of hydrate dissociation models. Specifically, the cumulative gas production and methane generation rate values obtained are relatively diminished when neglecting capillary pressure between hydrate and water. Capillary pressure, hydrate dissociation effects, and the coupled effect of interphase heat transfer collectively influence the distribution of phase equilibrium pressure, methane generation rate, phase distribution, temperature distribution, and phase equilibrium pressure distribution. Capillary pressure elevates the phase equilibrium pressure of hydrate, augments the driving force for hydrate dissociation, and accelerates the dissociation process. • Hydrate dissociation model is proposed based on an improved phase equilibrium model. • Significance and necessity of considering capillary pressure are elucidated. • Coupling effects of capillary pressure and hydrate dissociation are studied. • Capillary pressure raises hydrate phase equilibrium pressure and dissociation rate. [ABSTRACT FROM AUTHOR]

• Colloidal particle clogging is caused by both deposition and aggregation. • Rough concave surfaces play a dominant role in particle deposition. • Surface clogging is the ultimate type of clogging if recharge time is unlimited. Groundwater recharge engineering practices are usually accompanied by the migration and deposition of polydisperse particles. Solid particles may be retained in the pore space leading to clogging of the porous media and reducing groundwater recharge efficiency. However, the mechanism behind this clogging phenomenon remains poorly understood. Specifically, the relation of particle clogging at pore-scale and macroscale is unclear. Here, the influence of polydisperse particle size on clogging development patterns was studied utilizing a series of laboratory-scale column experiments in conjunction with pore-scale scanning electron microscopy (SEM) experiments. Particles with median particle sizes (d p50) of 0.66, 4.05, 11.83 μm were injected separately into the sand column to simulate particle clogging that occurs during groundwater recharge. SEM was used to directly observe particles deposition on porous media grain surface after the column experiments. By counting the size distribution of the particles on the media grain surface, the response of the particle deposition to the surface morphology of the media grains was analysed. Compared to d p50 of 4.05 and 11.83 μm, the spatial distribution of particles deposited in the sand column was more uniform at d p50 of 0.66 μm. The smallest particles (d p50 = 0.66 μm) used in the experiments ultimately formed mixed clogging, which was the result of the combined effects of particle deposition and aggregation. The particle deposition with d p50 = 4.05 and 11.83 μm ultimately exhibited hyper-exponential distribution and formed mixed and superficial clogging, respectively. At the same time, the concave region of the media grain surface played a dominant role in particle deposition. For d p50 = 4.05 μm, 69.41 % of the particles were deposited in the concave region, and for d p50 = 11.83 μm, the proportion was 90.1 %. The results help to better manage particle clogging in groundwater recharge and other engineering applications (e.g., groundwater source heat pump, and filtration project). In addition, these findings provide a theoretical reference for the development of numerical models to help recognize the probability of particles of different sizes to be captured in porous media. [ABSTRACT FROM AUTHOR]

• An Eulerian-Lagrangian solver is developed using the OpenFOAM library. • The effects of Brownian, Van der Waals, and electrostatic forces are considered. • The deposition ratio of nanoparticles is investigated by the pore-scale approach. • Open-cell foams with various porosities and Berea sandstone are studied. Nanoparticle deposition in a subsurface environment decreases the amount of material in the bulk fluid, increases surface roughness, and affects nanofluid flow. Nanoparticle transport in porous media is a complex, multiscale phenomenon. Its macroscopic behavior is determined by phenomena at the pore-scale. Hence, it is necessary and of interest to study the transport and deposition of nanoparticles in porous media using a pore-scale approach. A computational solver is developed using an Eulerian-Lagrangian approach within the OpenFOAM library. A Berea sandstone and three open-cell metal foams with porosities of 0.8, 0.85, and 0.9, constructed by Laguerre-Voronoi tessellation, were analyzed to study nanoparticle behavior in water. Nanoparticle deposition on solid surfaces is influenced by porosity, double layer thickness (N DL), surface potential magnitude (N E1), and nanoparticle diameter. Brownian motion that has a significant impact on nanoparticle transport and deposition is also examined. For nanoparticles with 20 nm diameter, the fraction of particles deposited in foam with 0.8 porosity is about 17 % more than the foam with 0.9 porosity. This difference decreases with nanoparticle diameter. For the particles with 100 nm diameter and more, the effects of Brownian motion on nanoparticle deposition becomes negligible. [Display omitted] [ABSTRACT FROM AUTHOR]

The corrosion-induced permeability changes of nanoscale zero-valent iron (NZVI) are one of the crucial factors constraining the successful application of NZVI in the remediation of contaminated groundwater. It is of great significance to study the dynamic evolution of corrosion products of NZVI after NZVI is injected into porous media and its influence on pore plugging effect from the pore scale. Micro computed tomography (Micro-CT) imaging technology, mineralogical characterization and theoretical calculations were used to understand the details of NZVI corrosion plugging porous media at the pore scale. This study reveals the factors of NZVI corrosion plugging porous media, namely, gas production (H 2 ) in the early and middle stages of corrosion (before 90 days) and solid phase changes (NZVI volume increase and migration) in the later stages (after 90 days). The permeability loss rate of the porous media was 66.8%, 87.3%, 79.4%, and 53.6% at the corrosion times of 30, 60, 90, and 120 days, respectively. After 90 d of corrosion, the particle size of NZVI increases by 7.9%, and the secondary minerals formed by corrosion are mainly Fe 3 O 4 /γ-Fe 2 O 3 and FeOOH. In addition, this study also found that the migration of NZVI after 90 d was due to its corrosion reducing the magnetic attraction between particles, dissociating into smaller particles or agglomerates under the action of fluid dynamics, resulting in its redistribution in the porous medium and causing blockage. This study clarifies that NZVI corrosion plays a vital influence in affecting the permeability and clogging of porous media, providing valuable guidance for optimizing NZVI-based remediation technologies., Competing Interests: Declaration of competing interest The author declares that the research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Taking the non-stick coal from Yangchangwan Coal Mine as the research object, based on the micro-CT scanning experiment and Avizo processing software, the pore-fracture, minerals and coal matrix of the coal are accurately extracted and segmented. Through the three-dimensional reconstruction technology, the connected pores and fracture models are obtained. On this basis, an equivalent pore network model（PNM）with the morphological topological structure of pores and fractures was further established, and the pore-throat structure parameters in the coal were statistically analyzed, including pore radius, pore volume, throat radius, throat length, and coordination number. Based on the pore-scale seepage simulation, the visualization seepage of single-phase water in the pore-fracture space was realized, and the absolute permeability in three directions was calculated. The results show that the Yangchangwan non-stick coal is dominated by flaky pore clusters and large-scale vertical fractures. The average pore radius and throat radius is 106 μm and 27.79 μm, respectively, and the average coordination number is 3.45. In the process of single-phase water seepage, the seepage velocity in the pore-fracture space is higher than that of the outlet and inlet, and the permeability in the three directions shows obvious anisotropy. Among them, the absolute permeability value in the y direction is the largest, and in the x direction is the smallest.

We investigate reactive flow and transport in evolving porous media. Solute species that are transported within the fluid phase are taking part in mineral precipitation and dissolution reactions for two competing mineral phases. The evolution of the three phases is not known a-priori but depends on the concentration of the dissolved solute species. To model the coupled behavior, phase-field and level-set models are formulated. These formulations are compared in three increasingly challenging setups including significant mineral overgrowth. Simulation outcomes are examined with respect to mineral volumes and surface areas as well as derived effective quantities such as diffusion and permeability tensors. In doing so, we extend the results of current benchmarks for mineral dissolution/precipitation at the pore-scale to the multiphasic solid case. Both approaches are found to be able to simulate the evolution of the three-phase system, but the phase-field model is influenced by curvature-driven motion. [ABSTRACT FROM AUTHOR]

A pore-scale numerical simulation for combustion of methane-air mixtures in a two-layer porous media burner made of staggered arrangement of connected particles is preformed. Combustion is modeled by a one-step reaction mechanism, and solid surface radiation heat transfer is computed by discrete ordinates (DO) model. The bridge approach is used to deal with the point contact between adjacent particles. The present study is intended to investigate the non-equilibrium characteristics of gas velocity and temperature under two operating parameters such as the inlet velocity and equivalence ratio. A comparison of the numerical values and experimental values was carried out to prove the effectiveness of numerical model, and a good agreement is shown. The results showed considerable non-equilibrium of velocity and temperature along the space coordinate due to the inhomogeneous porous structure. The extent of flow non-equilibrium increases as inlet velocity and equivalence ratio are increased. The extent of gas temperature non-equilibrium decreases slightly with the inlet velocity, but the equivalence ratio effect on thermal non-equilibrium can be neglected.

We present two novel Volume-of-Solid (VoS) formulations for micro-continuum simulation of mineral dissolution at the pore-scale. The traditional VoS formulation (VoS-ψ) uses a diffuse interface localization function ψ to ensure stability and limit diffusion of the reactive surface. The main limitation of this formulation is that accuracy is strongly dependent on the choice of the localization function. Our first novel improved formulation (iVoS) uses the divergence of a reactive flux to localize the reaction at the fluid-solid interface, so no localization function is required. Our second novel formulation (VoS-ψ′) uses a localization function with a parameter that is fitted to ensure that the reactive surface area is conserved globally. Both novel methods are validated by comparison with experiments, numerical simulations using an interface tracking method based on the Arbitrary Eulerian Lagrangian (ALE) framework, and numerical simulations using the VoS-ψ. All numerical methods are implemented in GeoChemFoam, our reactive transport toolbox and three benchmark test cases in both synthetic and real pore geometries are considered: 1) dissolution of a calcite post by acid injection in a microchannel and experimental comparison, 2) dissolution in a 2D polydisperse disc micromodel at different dissolution regimes and 3) dissolution in a Ketton carbonate rock sample and comparison to in-situ micro-CT experiments. We find that the iVoS results match accurately experimental results and simulation results obtained with the ALE method, while the VoS-ψ method leads to inaccuracies that are mostly corrected by the VoS-ψ’ formulation. In addition, the VoS methods are significantly faster than the ALE method, with a speed-up factor of between 2 and 12.

Triply periodic minimal surface (TPMS) can control the structural characteristic parameters through implicit functions, which possesses great significance for the customization of porous matrix topologies used in transpiration cooling. An innovative geometric reconstruction and meshing method is developed to reconstruct different TPMS porous matrix, a pore-scale numerical simulation of transpiration cooling coupled with mainstream is performed, and a hot wind tunnel experiment is developed to validate the numerical method. The main conclusions are as follows: The flow resistance loss of coolant within porous matrix is greatly influenced by the shape and size of pore throat, and due to the interaction between mainstream and coolant, higher flow resistance loss doesn't mean a higher coolant injection pressure. The influence of pore morphology on cooling efficiency is more obvious at higher coolant dosage, and considering the coolant injection pressure and cooling efficiency at the same time, the W(B) structure shows the best comprehensive performance. The generation of counter-rotating vortex pairs (CRVPs) in coolant film might lead to the increase in skin-friction coefficient on the structure surface, and the complex outflow angle of coolant can inhibit the generation of CRVPs, so for the case needs to reduce the skin-friction resistance, W(A) structure is recommended. [ABSTRACT FROM AUTHOR]

• A in-situ visualization protocol for pore-scale distribution of MAOM was developed. • The mobility of clay-sized MAOM was lower in the intra-aggregate zones. • Considerable amounts of MAOM in intra-aggregate zone was retained after leaching. • Colloid facilitated transport dominates the mobility of clay-sized MAOM. The mobility of different types of soil organic matter (SOM), including dissolved organic matter (DOM) and mineral associated organic matter (MAOM), along the soil profile in response to infiltration flow can significantly affect the carbon pools in subsoil. In addition, the soil heterogeneity on the pore-scale, comprising pore spaces within the intra-aggregate matrix and preferential pathways within inter-aggregate zones, can also affect the mobility of SOM. This is especially the case for clay-sized MAOM. However, the quantitative understanding of the clay-sized MAOM mobility in presence of pore-scale heterogeneity remains elusive. This study designed a novel microfluidic device to track the pore-scale distribution and mobility of fluorescence labeled clay-sized MAOM in heterogeneous soil pore structures. Results showed that the MAOM mobility was significantly lower in the intra-aggregate zones compared with in the inter-aggregate zones. Only 4.8 % to 47.9 % of MAOM in the intra-aggregate region was mobilized at high leaching flow rates of 81 to 163 mm/d. Moreover, colloid mobilization induced by shearing rather than solute desorption followed by solute dilution is expected to be the major factor facilitating the mobilization of clay-sized MAOM. This study demonstrated a new experimental protocol allowing the in-situ visualization and quantification of OMs mobility in presence of pore-scale heterogeneity. Moreover, our findings also highlighted the potential importance of heterogeneous mobility of clay-sized MAOMs that facilitated by the colloid transport on the SOM turnover and distribution. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dioxide-enhanced oil recovery (CO 2 -EOR) is an important means of improving oil recovery while lowering greenhouse gas emissions. However, it is still challenging to determine the pore-scale flow characteristics and interfacial interaction parameters, such as the wettability, interfacial curvature, and capillary pressure, under near-miscible conditions. In this study, X-ray microtomography (micro-CT) was used to determine the morphology of gas and oil phases and characterize the in-situ wettability under near-miscible conditions. The mean contact angle increased from 66.99° to 72.5° as the injected CO 2 pore volume (PV) increased from 5.5 PV to 33.1 PV. The wettability was locally altered as the local contact angle changed from 44.14° to 107.27° because of preferential adsorption of CO 2 molecules over oil molecules on solid surfaces. The mixed-wet condition was reflected by local contact angles both below and above 90°, and the capillary pressure exhibited a tower-shaped distribution with a peak value around zero, which promoted oil recovery. At the end of the displacement process, the interfaces were pushed toward the corners by a reduction in the capillary pressure, resulting in interface recession and a reduction in CO 2 clusters. Pore occupancy studies showed that under near-miscible conditions, gas usually occupies large pores and oil resides in pores of varying sizes, which can result in optimal recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrate phase transition and gas–water multi-phase flow were examined under pore-scale. • A LBM model of clayey silt hydrate-bearing sediment pore structure was constructed. • A quantitative description of the relationship between relative permeability and hydrate saturation was included. Unlike conventional oil and gas sources, natural gas hydrate (NGH) is stored in solid form within the pores of loose submarine sediments. Production by any method poses a complex problem involving phase transition and multi-phase flow of gas and water. The evolution of hydrate dissociation from the solid phase to gas and liquid phases in a hydrate reservoir is a dynamic process incorporating pore structure and multi-phase seepage. The solid–gas-liquid phase dissociation of NGH affects reservoir seepage properties by altering the micropore structure of the hydrate-bearing sediments. This study, based on the lattice Boltzmann method of modeling fluids flow, clearly demonstrates the micropore-scale changes in pressure and heat transfer that take place during hydrate dissociation. Pore-scale heterogeneity is found to influence the complex development of hydrates in a porous clayey silt medium during dissociation. The effect of hydrate, gas and water saturation on the evolution of relative permeability is identified, and the relationship between relative permeability and hydrate saturation during hydrate dissociation is quantified. These findings provide theoretical support for the implementation of marine natural gas hydrate production testing and future commercial production in China. [ABSTRACT FROM AUTHOR]

• Pore-scale modeling on the natural convection in reconstructed porous media. • The critical pore size where natural convection become significant is determined. • Effects of pore structure and heating direction on critical pore size are explored. • A general criterion is proposed to determine the significance of natural convection. Heat conduction in porous media is generally accompanied by the natural convection of the fluid within the pores driven by the temperature gradient. However, the criterion to determine the critical pore size of porous media where the natural convection cannot be neglected remains elusive. In this study, a pore-scale model is established to investigate the contributions of natural convection on the effective thermal conductivity (ETC) of porous media, which takes the reconstructed microstructures as the geometry input. We thus examine the effects of the porosity, thermal conductivity of the fluid and solid phases, and heating direction on the critical pore size where the natural convection starts to work. The results show that the critical pore size decreases with increasing porosity and heating temperature, but increases with the rise in the thermal conductivity of solid phase. Moreover, the critical pore size is significantly lower for the lateral heating, compared with the bottom heating. Finally, we proposed a new formula as an indicator to determine the significance of natural convection to the heat transfer in porous media. [ABSTRACT FROM AUTHOR]

We study pore-scale gas bubble ripening in porous media by combining a mass transfer method based on chemical potential differences with a level-set method for updating the gas/liquid configurations. We examine the impact of pore geometry and initial gas bubble distribution on the evolution, as well as the effect of mesh refinement and numerical parameters controlling the adaptive time steps in the model. Our results show that the pore geometry has a significant impact as it determines the rate of bubble pressure change with volume, while the area for mass transfer influences the time scale of the evolution. Simulations with different spatial patterns of bubbles with high and low pressures yield different ripening behaviors, classified as local and global ripening regimes. Simulations on sandstone with volumetrically similar bubble distributions display different ripening paths depending on the initial bubble locations, emphasizing the importance of capturing displacement history before ripening investigations. [Display omitted] • Pore throat geometry impacts bubble pressure–volume relations and ripening rates. • Bubble population ripening regime depends on the initial spatial distribution. • Different gas-bubble populations ripen at different rates and evolve differently. [ABSTRACT FROM AUTHOR]

Microorganisms capable of biomineralization can catalyze mineral precipitation by modifying local physical and chemical conditions. In porous media, such as soil and rock, these microorganisms live and function in highly heterogeneous physical, chemical and ecological microenvironments, with strong local gradients created by both microbial activity and the pore-scale structure of the subsurface. Here, we focus on extracellular bacterial biomineralization, which is sensitive to external heterogeneity, and review the pore-scale processes controlling microbial biomineralization in natural and engineered porous media. We discuss how individual physical, chemical and ecological factors integrate to affect the spatial and temporal control of biomineralization, and how each of these factors contributes to a quantitative understanding of biomineralization in porous media. We find that an improved understanding of microbial behavior in heterogeneous microenvironments would promote understanding of natural systems and output in diverse technological applications, including improved representation and control of fluid mixing from pore to field scales. We suggest a range of directions by which future work can build from existing tools to advance each of these areas to improve understanding and predictability of biomineralization science and technology. [ABSTRACT FROM AUTHOR]

In this work, a hybrid method coupling a pseudo-potential lattice Boltzmann model (LBM) and a pore network model (PNM) to simulate drying in porous media is proposed. Based on the watershed method, the porous medium is firstly decomposed into pore regions. According to the liquid–vapor phase distribution at a given time, the pore regions are further divided into four pore types, namely two-phase pores where a liquid–vapor interface exists, buffer pores next to the two-phase pores, single-liquid and single-vapor phase pores. The pseudo-potential LBM is used in the two-phase and buffer pores to simulate liquid drying and track the movement of the interfaces, while the single-phase PNM simulations are conducted in the buffer and single-phase pores to simulate vapor or liquid flow. LBM and PNM are coupled in the buffer pores through exchange of boundary information. The hybrid method is applied to simulate liquid drying in a porous medium. The whole-domain LBM simulation is considered as the reference solution to validate the hybrid method. Liquid saturation variation during the drying process and detailed phase and pressure distributions obtained by the two methods match quite well, demonstrating the accuracy of the hybrid method. For the specific case studied, the hybrid method saves more than 60% computational time compared to the whole-domain LBM simulation. In addition, the speedup of the hybrid method becomes more significant for a larger computational domain. In summary, the hybrid method developed in this work combines the accuracy of LBM and the efficiency of PNM to simulate drying in porous media at pore scale and can lead to significant reduction of computation time, thus allowing the pore-scale consideration of drying in larger porous systems. [ABSTRACT FROM AUTHOR]

In this work, the pore‐scale dynamics of immiscible displacement of ScCO2–brine in a homogeneous pore network is studied using the volume of fluid method. The simulation results are verified with the theoretical equation and literature experimental data. First, the pore‐space filling is performed in a unit pore cell having an equal and unequal pore throat for both drainage and spontaneous imbibition. It is observed that the pore‐space filling sequence for drainage follows the rules described by the Young‐Laplace equation whereas the filling sequence did not follow the rule for spontaneous imbibition. Secondly, the simulation is performed for a homogeneous pore network. It is found that the transverse average volume fraction of ScCO2 from the simulation matches with the experimental data for intermediate and higher capillary numbers. Further, the present simulation is extended to study the flow regime identification and viscosity ratio and contact angle effects on ScCO2 volume fraction profile. [ABSTRACT FROM AUTHOR]

Holistic understanding of multiphase reactive flow mechanisms such as CO2 dissolution, multiphase displacement, and snap-off events is vital for optimisation of large-scale industrial operations like CO2 sequestration, enhanced oil recovery, and geothermal energy. Recent advances in three-dimensional (3D) printing allow for cheap and fast manufacturing of complex porosity models, which enable investigation of specific flow processes in a repeatable manner as well as sensitivity analysis for small geometry alterations. However, there are concerns regarding dimensional fidelity, shape conformity and surface quality, and therefore, the printing quality and printer limitations must be benchmarked. We present an experimental investigation into the ability of 3D printing to generate custom-designed micromodels accurately and repeatably down to a minimum pore-throat size of 140 μm, which is representative of the average pore-throat size in coarse sandstones. Homogeneous and heterogeneous micromodel geometries are designed, then the 3D printing process is optimised to achieve repeatable experiments with single-phase fluid flow. Finally, Particle Image Velocimetry is used to compare the velocity map obtained from flow experiments in 3D printed micromodels with the map generated with direct numerical simulation (OpenFOAM software) and an accurate match is obtained. This work indicates that 3D printed micromodels can be used to accurately investigate pore-scale processes present in CO2 sequestration, enhanced oil recovery and geothermal energy applications more cheaply than traditional micromodel methods. [ABSTRACT FROM AUTHOR]

In various natural and engineered systems, mineral–fluid interactions take place in the presence of multiple fluid phases. While there is evidence that the interplay between multiphase flow processes and reactions controls the evolution of these systems, investigation of the dynamics that shape this interplay at the pore scale has received little attention. Specifically, continuum scale models rarely consider the effect of multiphase flow parameters on mineral reaction rates or apply simple corrections as a function of the reactive surface area or saturation of the aqueous phase, without developing a mechanistic understanding of the pore-scale dynamics. In this study, we developed a framework that couples the two-phase flow simulator of OpenFOAM (open field operation and manipulation) with the geochemical reaction capability of CrunchTope to examine pore-scale dynamics of two phase flow and their impacts on mineral reaction rates. For our investigations, flat 2D channels and single sine wave channels were used to represent smooth and rough geometries. Calcite dissolution in these channels was quantified with single phase flow and two phase flow at a range of velocities. We observed that the bulk calcite dissolution rates were not only affected by the loss of reactive surface area as it becomes occupied by the non-reactive non-aqueous phase, but also largely influenced by the changes in local velocity profiles, e.g., recirculation zones, due to the presence of the non-aqueous phase. The extent of the changes in reaction rates in the two-phase systems compared to the corresponding single phase system is dependent on the flow rate (i.e., capillary number) and channel geometry, and follows a non-monotonic relationship with respect to aqueous saturation. The pore-scale simulation results highlight the importance of interfacial dynamics in controlling mineral reactions and can be used to better constrain reaction rate descriptions in multiphase continuum scale models. These results also emphasize the need for experimental studies that underpin the development of mechanistic models for multiphase flow in reactive systems.