Global well-posedness to non-isothermal porous media system

Methane hydrate formation in porous media: Overview and perspectives

Modelling clogging dynamics in groundwater systems using multiscale homogenized physics informed neural network (MHPINN)

ABSTRACTCO2 replacement method is an auspicious method for the CH4 extraction from gas hydrate and the CO2 geological storage into sediments. The replacement of CO2CH4 hydrate in porous medium system is jointly affected by many factors such as heat transfer, mass transfer, and reaction. It is of great significance to deeply understand the mechanism and dynamics of different factors influencing the replacement characteristics of CO2CH4 hydrate in porous media. In this study, the molecular dynamics simulation method was employed to study the replacement characteristics and kinetic process of CO2CH4 hydrate in porous medium system with varying conditions expecting to offer significant theoretical direction and a point of reference for the CO2 replacement method of natural gas hydrate extraction in permafrost regions in reality. The quantitative influence and internal mechanism of different factors on the replacement process of CO2CH4 hydrate were revealed. The results show that, in the porous medium system, when the temperature was ranged of 265–270 K and the pressure was ranged of 10–20 MPa, the replacement effect of CO2CH4 hydrate is the best under the initial concentration of CO2 of 100%. It was further indicated that the replacement effect is appropriate when the initial concentration of CO2 was ranged of 40%–60% under the case of 265 K and 10 MPa. Moreover, the result also indicated that the effects of some certain factors, including temperature, pressure, and initial concentration of CO2 on the replacement process of CO2CH4 hydrate, exist slightly different. Owing to the adsorption effect of porous media on CO2 molecules, it reduced the replacement efficiency between CO2CH4 hydrate. Additionally, the initial concentration of CO2 imposed a more significant influence on the replacement of CO2CH4 hydrate in porous medium system considering the adsorption effect of porous. It does not mean that the higher the initial concentration of CO2, the better the replacement effect of hydrate. The diffusion capacity of CO2 depends on the concentration of H2O molecules and the adsorption effect of porous media.

We focus on the inter-related roles of scale and heterogeneity of porous medium properties for fluid flow and contaminant transport in isothermal and non-isothermal multiphase systems across a range of scales. Multiscale network and macro-scale continuum models, and detailed laboratory experiments are used to support the investigation. We demonstrate the critical role of scale in determining the dominant forces in a porous medium system, the importance of heterogeneity across a range of scales, and the dominant role of block heterogeneities on macro-scale fluid flow and non-isothermal contaminant remediation. We give special attention to the numerical approximations of pressure-saturation-conductivity relations in heterogeneous systems, and we show the effects of interface approximation schemes on both the ability to resolve phenomena of concern and on the efficiency of the numerical simulator.

As an essential greenhouse gas, CO2 is the leading cause of global warming and environmental problems. An efficient strategy to lower CO2 emissions is the hydrate‐based method of CO2 geological storage. The stability and formation process of hydrate is the premise and foundation of the hydrate method of CO2 geological storage. However, the formation rule of CO2 hydrate has a significant impact on the formation characteristics of CO2 hydrate. This paper thoroughly examines the formation properties of CO2 hydrate in porous media systems. The quantitative impacts and laws of many parameters on the CO2 hydrate production process are thoroughly examined. On this basis, the internal mechanism of particle size, pore distribution, and critical size of particles in porous media systems on the kinetics of CO2 hydrate formation are detailed. Finally, the shortcomings of the studies on CO2 hydrate formation kinetics in porous media systems and the main directions in the future are pointed out. The influence of pore distribution in porous media on the CO2 hydrate formation process still needs further study. The relative results will be useful in the future for CO2 capture and sequestration in sediments. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

In this paper, experimental and numerical studies were conducted to differentiate solvent exsolution and liberation processes from different heavy oil–solvent systems in bulk phases and porous media. Experimentally, two series of constant-composition-expansion (CCE) tests in a PVT cell and differential fluid production (DFP) tests in a sandpacked model were performed and compared in the heavy oil–CO2, heavy oil–CH4, and heavy oil–C3H8 systems. The experimental results showed that the solvent exsolution from each heavy oil–solvent system in the porous media occurred at a higher pressure. The measured bubble-nucleation pressures (Pn) of the heavy oil–CO2 system, heavy oil–CH4 system, and heavy oil–C3H8 system in the porous media were 0.24 MPa, 0.90 MPa, and 0.02 MPa higher than those in the bulk phases, respectively. In addition, the nucleation of CH4 bubbles was found to be more instantaneous than that of CO2 or C3H8 bubbles. Numerically, a robust kinetic reaction model in the commercial CMG-STARS module was utilized to simulate the gas exsolution and liberation processes of the CCE and DFP tests. The respective reaction frequency factors for gas exsolution (rffe) and liberation (rffl) were obtained in the numerical simulations. Higher values of rffe were found for the tests in the porous media in comparison with those in the bulk phases, suggesting that the presence of the porous media facilitated the gas exsolution. The magnitudes of rffe for the three different heavy oil–solvent systems followed the order of CO2 > CH4 > C3H8 in the bulk phases and CH4 > CO2 > C3H8 in the porous media. Hence, CO2 was exsolved from the heavy oil most readily in the bulk phases, whereas CH4 was exsolved from the heavy oil most easily in the porous media. Among the three solvents, CH4 was also found most difficult to be liberated from the heavy oil in the DFP test with the lowest rffl of 0.00019 min−1. This study indicates that foamy-oil evolution processes in the heavy oil reservoirs are rather different from those observed from the bulk-phase tests, such as the PVT tests.

The entrapment of nonwetting phase fluids in unconsolidated porous media systems is strongly dependent on the porescale geometry and topology. Synchrotron X-ray tomography allows us to nondestructively obtain high-resolution (on the order of 1-10 micron), three-dimensional images of multiphase porous media systems. Over the past year, a number of multiphase porous media systems have been imaged using the synchrotron X-ray tomography station at the GeoSoilEnviroCARS beamline at the Advanced Photon Source. For each of these systems, we are able to: (1) obtain the physically-representative network structure of the void space including the pore body and throat distribution, coordination number, and aspect ratio; (2) characterize the individual nonwetting phase blobs/ganglia (e.g., volume, sphericity, orientation, surface area); and (3) correlate the porous media and fluid properties. The images, data, and network structure obtained from these experiments provide us with a better understanding of the processes and phenomena associated with the entrapment of nonwetting phase fluids. Results from these experiments will also be extremely useful for researchers interested in interphase mass transfer and those utilizing network models to study the flow of multiphase fluids in porous media systems.

We derive a novel two-phase flow system in porous media as a relaxation limit of compressible multi-fluid systems. Considering a one-velocity Baer–Nunziato system with friction forces, we first justify its pressure-relaxation limit toward a Kapila model in a uniform manner with respect to the time-relaxation parameter associated with the friction forces. Then, we show that the diffusely rescaled solutions of the damped Kapila system converge to the solutions of the new two-phase porous media system as the time-relaxation parameter tends to zero. In addition, we also prove the convergence of the Baer–Nunziato system to the same two-phase porous media system as both relaxation parameters tend to zero. For each relaxation limit, we exhibit sharp rates of convergence in a critical regularity setting. Our proof is based on an elaborate low-frequency and high-frequency analysis via the Littlewood–Paley decomposition and includes three main ingredients: a refined spectral analysis of the linearized problem to determine the frequency threshold explicitly in terms of the time-relaxation parameter, the introduction of an effective flux in the low-frequency region to overcome the loss of parameters due to the overdamping phenomenon, and renormalized energy estimates in the high-frequency region to cancel higher-order nonlinear terms. To justify the convergence rates, we discover several auxiliary unknowns allowing us to recover crucial O(ε) bounds.

Two different coupling approaches for isothermal single-phase free flow and isothermal single-fluid-phase porous medium systems are considered: sharp interface and transition region approach. The sharp interface concept implies the Beavers–Joseph–Saffman velocity jump condition together with restrictions that arise due to mass conservation and balance of normal forces across the fluid-porous interface. The transition region model is derived by means of the thermodynamically constrained averaging theory (TCAT). The equations are averaged over the thickness of the transition zone in the direction normal to the free flow and porous medium domains being joined. Coupling conditions are the mass conservation, the momentum balance and a generalization of the Beavers–Joseph condition. Two model formulations are compared and numerical simulation results are presented. For discretization of the coupled problem the finite volume method on staggered grids is used.

In this study, we investigated the crystallization of a salt mixture during drying in a porous medium. Specifically, we focused on the ternary system of NaCl-NaNO3-H2O, which is also encountered in situ. In order to study the crystallization, we use a specialized 4.7 T NMR setup that allows us to directly measure the NaCl and NaNO3 concentrations in a porous medium and track their ratio during drying, providing direct insight into the phase diagram. The measurements indicate that the equilibrium phase diagram alone is not sufficient to describe the physical processes that occur in porous media during drying experiments. In the case of forced drying in this study, where advection of the ions is dominant (Pe > 5), the measurements indicate that we need to take supersaturation into account and that crystallization is driven by transport. As a result, the ratio of a salt mixture will remain constant in the porous medium throughout the experiments, as was seen for this ternary system Na+, Cl-, NO3 - resulting in the formation of both NaCl and NaNO3. These results indicate that the rate of evaporation, in combination with the effect of supersaturation and solution transport in the pore system, allows the saturation degree given by the phase diagram to be surpassed. This phenomenon is critical when assessing mixed salt systems in porous media and should be considered when evaluating phase diagrams alone.

The solid system in deformable porous media undergoes deformation with the flow of fluid. In this paper, in order to study the micro-mechanism of the deformation, the solid system in the porous media is represented by a pack of spherical particles and simulated by discrete element method. The fluid system in the porous media is also simulated by computational fluid dynamics. To consider the fluid–particle interactions in the porous media, the above techniques are coupled and applied for simulating the solid deformation and fluid flow. Different models consisting of different particle sizes are studied in dry (without the presence of fluid) and wet states (with the flow of fluid). The results show that with the decrease in the particle size, the solid deformation declines, which imitates the actual deformation in the porous media. More importantly, the comparison between the dry and wet models indicates that the effect of the fluid on the particle system is diminishing with the smaller packed particles. The solid deformation tendency is quantified by the reduction in the values of some micro-mechanical properties, such as permeability (absolute and relative), porosity and pore-size distribution.

Heat transfer and fluid flow in rotating porous media

Chemical flooding is important and effective enhanced oil recovery processes are applied to improve the recovery of heavy oil reservoirs. Emulsification occurs during chemical flooding processes, forming an oil-in-water (O/W) emulsion system. In this work, the heavy oil emulsion system is characterized as a three-phase (continuous oil phase, dispersed oil phase, and continuous water phase) system. Based on a capillary tube model, a new relative permeability model is proposed to describe the flow of the emulsion system in porous media quantitatively, considering the physicochemical properties of emulsions and the properties of porous media. A resistance factor is derived in this model to describe the additional resistance to the emulsion flow caused by the interaction between dispersed oil droplets and the pore system. Three dimensionless numbers related to the emulsion porous flow process were proposed and their different effects on the three-phase relative permeability are investigated. To validate the reliability of the proposed model, a one-dimensional O/W emulsion–oil displacement experiment is simulated. The maximum absolute error between the simulated results and experimental data is no more than 10%, and the new model can be used to describe the flow behavior of heavy oil emulsions in porous media.

Effective thermal conductivity of highly porous two-phase systems

Modeling cross model non-Newtonian fluid flow in porous media