Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Gas migration in porous media.
Articles de revues sur le sujet « Gas migration in porous media »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Gas migration in porous media ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Mahabadi, Nariman, Xianglei Zheng, Tae Sup Yun, Leon van Paassen et Jaewon Jang. « Gas Bubble Migration and Trapping in Porous Media : Pore-Scale Simulation ». Journal of Geophysical Research : Solid Earth 123, no 2 (février 2018) : 1060–71. http://dx.doi.org/10.1002/2017jb015331.
Texte intégral
2
Van De Ven, C. J. C., et Kevin G. Mumford. « Visualization of gas dissolution following upward gas migration in porous media : Technique and implications for stray gas ». Advances in Water Resources 115 (mai 2018) : 33–43. http://dx.doi.org/10.1016/j.advwatres.2018.02.015.
Texte intégral
3
Wang, Yang, Ping Liu, Yangwen Zhu, Guanli Xu, Zijing Cui et Ruotong Du. « Effect of Janus nanoparticles on foam snap off in porous media ». Tenside Surfactants Detergents 61, no 3 (1 mai 2024) : 240–49. http://dx.doi.org/10.1515/tsd-2023-2573.
Texte intégralRésumé :
Abstract Nanoparticles can be adsorbed at the gas-liquid interface to improve the stability of foam. However, homogeneous nanoparticles exhibit low surface activity, and their migration to the gas-liquid interface requires significant energy input. This leads to harsh foaming conditions and severely limits the application of homogeneous nanoparticles in foam stability. A microfluidic visualisation model for the study of Janus nanoparticle complex systems was used to investigate the formation behaviour of trapped bubbles in a single connected pore-throat model. The foam generated in the pore showed reduced quantities, sizes, improved quality, and enhanced stability compared to both surfactant systems and hydrophilic nanoparticle complex systems.
4
Jung, Jongwon, Hongsig Kang, Shuang Cindy Cao, Riyadh I. Al-Raoush, Khalid Alshibli et Joo Yong Lee. « Effects of Fine-Grained Particles’ Migration and Clogging in Porous Media on Gas Production from Hydrate-Bearing Sediments ». Geofluids 2019 (23 mai 2019) : 1–11. http://dx.doi.org/10.1155/2019/5061216.
Texte intégralRésumé :
The migration of fine particles in porous media has been studied for different applications, including gas production from hydrate-bearing sediments. The clogging behavior of fine particles is affected by fine particle-pore throat size ratio, fine particle concentration, ionic concentration of fluids, and single/multiphase fluid flow. While previous studies presented valuable results, the data are not enough to cover a broad range of particle types and sizes and pore throat size in natural hydrate-bearing sediments. This paper presents a novel micromodel to investigate the effects of fine particle-pore throat size ratio, fine concentration, ionic concentration of fluid, and single/multiphase fluid flow on clogging or bridging in porous media. The results show that (1) the concentration of fine particles required to form clogging and/or bridging in pores decreased with the decrease in fine particle-pore throat size ratio, (2) the effects of ionic concentration of fluid on clogging behaviors depend on the types of fine particles, and (3) fine particles prefer to accumulate along the deionized water- (DW-) CO2 interface and migrate together, which in turn easily causes clogging in pores. As a result, multiphase fluid flow during gas production from hydrate-bearing sediments could easily develop clogging in pore throats, where the relative permeability of DW-CO2 in porous media decreases. Accordingly, the relatively permeability of porous media should be evaluated by considering the clogging behavior of fines.
5
Peng, Zhigao, Shenggui Liu, Songlei Tang, Yuechao Zhao et Yingjun Li. « Multicomponent Lattice Boltzmann Simulations of Gas Transport in a Coal Reservoir with Dynamic Adsorption ». Geofluids 2018 (12 juillet 2018) : 1–13. http://dx.doi.org/10.1155/2018/5169010.
Texte intégralRésumé :
Gas adsorption occurs when the dynamic adsorption equilibrium conditions of the local adsorptive sites are broken. In the overall process of unconventional natural gas generation, enrichment, storage, and production, this phenomenon plays a significant role. A double-distribution Lattice Boltzmann model for solving the coupled generalized Navier-Stokes equation and advection-diffusion equation with respect to the gas-solid dynamic adsorption process is proposed for multicomponent gas migration in the unconventional reservoir. The effective diffusion coefficient is introduced to the model of gas transport in the porous media. The Langmuir adsorption rate equation is employed to control the adsorption kinetic process of gas-solid adsorption/desorption. The model is validated in two steps through fluid flow without and with gas diffusion-adsorption between two parallel plates filled with porous media, respectively. Simulation results indicate that with other parameters being equal, the rate of gas diffusion in the porous material and the area of the dynamic adsorption equilibrium-associated region increase with the matrix porosity/permeability. Similar results will happen with a greater saturation adsorption amount or a lower Langmuir pressure. The geometric effect on adsorption is also studied, and it is found that a higher specific surface area or free flow region can enhance the gas transport and the rate of adsorption.
6
MEAKIN, PAUL, GERI WAGNER, VIDAR FRETTE, JENS FEDER et TORSTEIN JØSSANG. « FRACTALS AND SECONDARY MIGRATION ». Fractals 03, no 04 (décembre 1995) : 799–806. http://dx.doi.org/10.1142/s0218348x95000709.
Texte intégralRésumé :
The process of secondary migration, in which oil and gas are transported from the source rocks, through water saturated sedimentary carrier rocks, to a trap or reservoir can be described in terms of the gravity driven penetration of a low-density non-wetting fluid through a porous medium saturated with a wetting fluid. This process has been modeled in the laboratory and by computer simulations using homogeneous porous media. Under these conditions, the pattern formed by the migrating fluid can be described in terms of a string of fractal blobs. The low density internal structure of the fractal blobs and the concentration of the transport process onto the self-affine strings of blobs (migration channels) both contribute to the small effective hydrocarbon saturation in the carrier rocks. This allows the hydrocarbon fluids to penetrate the enormous volume of carrier rock without all of the hydrocarbon being trapped in immobile isolated bubbles. In practice, heterogeneities in the carrier rocks play an important role. In some cases, these heterogeneities can be represented by fractal models and these fractal heterogeneity models provide a basis for more realistic simulations of secondary migration. Fractures may play a particularly important role and migration along open fractures was simulated using a self-affine fractal model for the fluctuating fracture aperture.
7
Ezeuko, C. C., et S. R. McDougall. « Modeling Flow Transitions during Buoyancy-Driven Gas Migration in Liquid-Saturated Porous Media ». Vadose Zone Journal 9, no 3 (août 2010) : 597–609. http://dx.doi.org/10.2136/vzj2009.0037.
Texte intégral
8
Masum, S. A., P. J. Vardon, H. R. Thomas, Q. Chen et D. Nicholson. « Multicomponent gas flow through compacted clay buffer in a higher activity radioactive waste geological disposal facility ». Mineralogical Magazine 76, no 8 (décembre 2012) : 3337–44. http://dx.doi.org/10.1180/minmag.2012.076.8.46.
Texte intégralRésumé :
AbstractAt the post-closure stage of a geological disposal facility for higher activity radioactive waste several species of gas are likely to be generated in the near-field environment. These could alter the sealing and chemical properties of the bentonite buffer and the local geochemical environment significantly. The authors' attempt to simulate multicomponent gas flow through variably saturated porous media is presented. Governing equations have been developed for a reactive gas-flow model to simulate the thermo-hydro-gas-chemical-mechanical behaviour, with specific reference to the performance of highly compacted bentonite buffer subjected to repository gas generation and migration. The developed equations have been included in the bespoke numerical model COMPASS and some generic simulations are also presented. The model presented extends current capability to assess buffer performance.
9
Munholland, Jonah L., Kevin G. Mumford et Bernard H. Kueper. « Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating ». Journal of Contaminant Hydrology 184 (janvier 2016) : 14–24. http://dx.doi.org/10.1016/j.jconhyd.2015.10.011.
Texte intégral
10
An, Huaming, Ruyue Gong, Xingxing Liang et Hongsheng Wang. « Numerical Simulation Study on Gas Migration Patterns in Ultra-Long Fully Mechanized Caving Face and Goaf of High Gas and Extra-Thick Coal Seams ». Fire 8, no 1 (31 décembre 2024) : 13. https://doi.org/10.3390/fire8010013.
Texte intégralRésumé :
The purpose of this study is to understand the law of gas migration in the goaf and reduce the gas on the working face. Taking the N2105 working face of the coal mining industry as the research object, the mathematical model of gas seepage in the goaf was established based on the percolation theory of porous media, and the model was solved. Using Fluent software to simulate the initial pressure, the working face airflow, and gas concentration distribution, different ventilation modes of gas concentration distribution and migration law with different wind speeds after the initial gas pressure. It is concluded that for the first time, the effect of gas on the working face is insignificant, and the influence of the initial pressure on the working surface is gradually revealed. The influence of airflow speed on the goaf is mainly concentrated in the 20~30 m area near the working face, which is affected by the airflow speed of the working face. The gas concentration in the goaf is low, and the fluctuation is obvious. The types of ventilation directly affect the seepage law of goaf gas. The U + I and U + L type ventilation can reduce the gas concentration in the upper corner and f gas seepages from goaf to the working face.
11
Mei, Liang, Sune Svanberg et Gabriel Somesfalean. « Combined optical porosimetry and gas absorption spectroscopy in gas-filled porous media using diode-laser-based frequency domain photon migration ». Optics Express 20, no 15 (11 juillet 2012) : 16942. http://dx.doi.org/10.1364/oe.20.016942.
Texte intégral
12
Amaziane, Brahim, Leonid Pankratov et Andrey Piatnitski. « Homogenization of immiscible compressible two-phase flow in highly heterogeneous porous media with discontinuous capillary pressures ». Mathematical Models and Methods in Applied Sciences 24, no 07 (14 avril 2014) : 1421–51. http://dx.doi.org/10.1142/s0218202514500055.
Texte intégralRésumé :
This paper presents a study of immiscible compressible two-phase, such as water and gas, flow through highly heterogeneous porous media with periodic microstructure. Such models appear in gas migration through engineered and geological barriers for a deep repository for radioactive waste. We will consider a domain made up of several zones with different characteristics: porosity, absolute permeability, relative permeabilities and capillary pressure curves. Consequently, the model involves highly oscillatory characteristics and internal nonlinear interface conditions. The microscopic model is written in terms of the phase formulation, i.e. where the wetting (water) saturation phase and the non-wetting (gas) pressure phase are primary unknowns. This formulation leads to a coupled system consisting of a nonlinear parabolic equation for the gas pressure and a nonlinear degenerate parabolic diffusion-convection equation for the water saturation, subject to appropriate transmission, boundary and initial conditions. The major difficulties related to this model are in the nonlinear degenerate structure of the equations, as well as in the coupling in the system. Moreover, the transmission conditions are nonlinear and the saturation is discontinuous at interfaces separating different media. Under some realistic assumptions on the data, we obtain a nonlinear homogenized coupled system with effective coefficients which are computed via a cell problem and give a rigorous mathematical derivation of the upscaled model by means of the two-scale convergence.
13
Sarsembayeva A.S., Sarsembayeva A. S., Collins P. E. Collins P.E. et Slambekova Zh S. Slambekova Zh.S. « Vapour transfer in the freezing soils – physical phenomena of the frost heave ». Рroblems of engineering and professional education 57, no 2 (13 décembre 2022) : 10. http://dx.doi.org/10.32523/2220-685x-2020-57-2-10.
Texte intégralRésumé :
Study of the hydraulic conductivity in the freezing soils and the frost heave mechanism started as far as in the 30’s of the last century and even earlier. However explanation of frost heave mechanism with hydraulic conductivity is fundamentally wrong approach which lead
Study of the hydraulic conductivity in the freezing soils and the frost heave mechanism started as far as in the 30’s of the last century and even earlier. However explanation of frost heave mechanism with hydraulic conductivity is fundamentally wrong approach which leads to the complication in the calculations and the predictions of frost heave. The presented work explains the detailed description of the moisture migration in a gas phase within the freezing porous media and gives the mathematical modelling based on the phase transitions of moister as water–gas–water-ice. The proposed method is based on the thermodynamically and phases equilibrium and allows to determine the speed of the mass transfer in the freezing media. The calculations were shown in an example of the experimental testing data. The obtained results admit the strong relationship of the frost heave and air void volume. They also emphasize the impact of soil density, void ratio and moisture content on the amount of built ice in the freezing zone of the soil.
s to the complication in the calculations and the predictions of frost heave. The presented work explains the detailed description of the moisture migration in a gas phase within the freezing porous media and gives the mathematical modelling based on the phase transitions of moister as water–gas–water-ice. The proposed method is based on the thermodynamically and phases equilibrium and allows to determine the speed of the mass transfer in the freezing media. The calculations were shown in an example of the experimental testing data. The obtained results admit the strong relationship of the frost heave and air void volume. They also emphasize the impact of soil density, void ratio and moisture content on the amount of built ice in the freezing zone of the soil.
14
Mascle, Matthieu, Olivier Lopez, Herve Deschamps, Lars Rennan, Nicolas Lenoir, Alessandro Tengattini et Souhail Youssef. « Investigation of salt precipitation dynamic in porous media by X-ray and Neutron dual-modality imaging ». Science and Technology for Energy Transition 78 (2023) : 11. http://dx.doi.org/10.2516/stet/2023009.
Texte intégralRésumé :
In this work, a new dual modality monitoring technique is presented to demonstrate its interest to investigate the salt precipitation dynamics induced by gas flow-through drying. It consists of imaging simultaneously a core flood using both Neutron and X-ray beams. A method to calibrate and process the two signals is presented. It takes advantage of the difference in attenuation between the two ionizing radiations to quantify the different phase saturations and compositions as well as the reduction of porosity caused by salt precipitation. A set of experiments has been conducted at the NeXT-Grenoble beamline of the Institute Laue-Langevin facilities (ILL, France). Experiments were conducted on a homogeneous rock sample of Bentheimer sandstone using dry nitrogen and a 100 g/L KBr brine. The two first experiments aimed to calibrate the dual modality for the different phases. The last two experiments have been conducted with a brine capillary contact maintained at the gas outlet. Experimental data have given new insights into the organization of the three phases (the brine, the gas, and the precipitated salt) when a salt bank is formed in the sample. These quantities computed using dual-modality imaging show great similarities with published work. The salt accumulation was used to estimate the flow rate of brine pumped through the capillary contact to compensate for the brine evaporation in the gas phase. Observations have shown that a reduction of the initial porosity in some sections of the sample by 12–14% was enough to trigger a gas draw-down characterized by the migration of the salt toward the gas inlet. In some conditions (low gas inlet pressure for example), the rise of the water could be fast enough to form a second salt bank higher in the sample. It has been observed that the formation of the second salt bank could spread the precipitated salt in a less damaging configuration for the gas flow, triggering a phase of gas build-up characterized by the withdrawal of the water. These phases of gas draw-down and build-up could alternate until the sample clogs.
15
Narkuniene, Asta, Gintautas Poskas et Gytis Bartkus. « Modelling of the Corrosion-Induced Gas Impact on Hydraulic and Radionuclide Transport Properties of Geological Repository Barriers ». Minerals 14, no 1 (19 décembre 2023) : 4. http://dx.doi.org/10.3390/min14010004.
Texte intégralRésumé :
The geological disposal of high-level radioactive waste is the final step in the nuclear fuel cycle. It is realized via isolating the high-level radioactive waste in the geological environment with an appropriate system of engineered barriers. Radionuclides-containing materials must be isolated from the biosphere until the radioactivity contained in them has diminished to a safe level. In the case of high-level radioactive waste, it could take hundreds of thousands of years. Within such a long timescale, a number of physical and chemical processes will take part in the geological repository. For the assessment of radionuclide migration from a geological repository, it is necessary to predict the repository’s behavior once placed in the host rock as well as the host-rock response to disturbances due to construction. In this study, the analysis of repository barriers (backfill, concrete, inner excavation disturbed zone (EDZ), outer EDZ, host rock) thermo–hydraulic–mechanical (THM) evolution was performed, and the scope of gas-induced desaturation was analyzed with COMSOL Multiphysics. The analysis was based on modelling of a two-phase flow of miscible fluid (water and H2) considering important phenomena such as gas dissolution and diffusion, advective–diffusive transport in the gaseous phase, and mechanical deformations due to thermal expansion of water and porous media. The importance of proper consideration of temperature-dependent thermodynamic properties of water and THM couplings in the analysis of near-field processes was also discussed. The modelling demonstrated that such activities as 50 years’ ventilation of the waste disposal tunnel in initially saturated porous media, and such processes as gas generation due to corrosion of waste package or heat load from the waste, also led to desaturation of barriers. H2 gas generation led to the desaturation in engineered barriers and in a part of the EDZ close to the gas generation place vanishing soon after finish of gas generation, while the host rock remained saturated during the gas generation phase (50–100,000 years). Radionuclide transport properties in porous media such as effective diffusivity are highly dependent on the water content in the barriers determined by their porosity and saturation.
16
Ye, Yongjun, Wenhao Wu, Chunhua Huang et Kimberlee J. Kearfott. « Experimental study of the effect of seepage on radon exhalation in circular tubular porous emanation media ». Indoor and Built Environment 29, no 5 (4 juillet 2019) : 701–10. http://dx.doi.org/10.1177/1420326x19861781.
Texte intégralRésumé :
Radium, which is naturally present in many rocks, decays to the radioactive gas radon, which is then exhaled from the surface of underground tunnels and other underground buildings and is a major source of human exposure to radioactivity. A mathematical model for the migration of radon from a circular tubular emanation medium was established based on the seepage–diffusion migration theory for radon in porous emanation media, such as artificial retaining walls and the surrounding rocks in these locations. An analytical solution for the distribution of radon concentrations and the calculation formula for the radon exhalation rate under steady-state conditions were then obtained. An experimental device was designed to determine the radon exhalation rate under different pressure gradients. The theoretical calculation values for the radon exhalation rate and the total amount of radon exhalation are in good agreement with the experimental results. The radon exhalation rate at the low-pressure side increases with an increase in seepage velocity (pressure difference), while the radon exhalation rate at the high-pressure side is on the contrary. The total amount of radon exhalation increased over time with an increase in the seepage velocity and tended towards a maximum value.
17
Zhang, Moxi, Xinglong Chen et Weifeng Lyu. « Research on the Evolution Characteristics and Influencing Factors of Foamy Oil Bubbles in Porous Media ». Molecules 30, no 5 (5 mars 2025) : 1163. https://doi.org/10.3390/molecules30051163.
Texte intégralRésumé :
This study systematically investigates the formation mechanism and development characteristics of the “foamy oil” phenomenon during pressure depletion development of high-viscosity crude oil through a combination of physical experiments and numerical simulations. Using Venezuelan foamy oil as the research subject, an innovative heterogeneous pore-etched glass model was constructed to simulate the pressure depletion process, revealing for the first time that bubble growth predominantly occurs during the migration stage. Experimental results demonstrate that heavy components significantly delay degassing by stabilizing gas–liquid interfaces, while the continuous gas–liquid diffusion effect explains the unique development characteristics of foamy oil—high oil recovery and delayed phase transition—from a microscopic perspective. A multi-scale coupling analysis method was established: molecular-scale simulations were employed to model component diffusion behavior. By improving the traditional Volume of Fluid (VOF) method and introducing diffusion coefficients, a synergistic model integrating a single momentum equation and fluid volume fraction was developed to quantitatively characterize the dynamic evolution of bubbles. Simulation results indicate significant differences in dominant controlling factors: oil phase viscosity has the greatest influence (accounting for ~50%), followed by gas component content (~35%), and interfacial tension the least (~15%). Based on multi-factor coupling analysis, an empirical formula for bubble growth incorporating diffusion coefficients was proposed, elucidating the intrinsic mechanism by which heavy components induce unique development effects through interfacial stabilization, viscous inhibition, and dynamic diffusion. This research breaks through the limitations of traditional production dynamic analysis, establishing a theoretical model for foamy oil development from the perspective of molecular-phase behavior combined with flow characteristics. It not only provides a rational explanation for the “high oil production, low gas production” phenomenon but also offers theoretical support for optimizing extraction processes (e.g., gas component regulation, viscosity control) through quantified parameter weightings. The findings hold significant scientific value for advancing heavy oil recovery theory and guiding efficient foamy oil development. Future work will extend to studying multiphase flow coupling mechanisms in porous media, laying a theoretical foundation for intelligent control technology development.
18
Faybishenko, Boris, Yifeng Wang, Jon Harrington, Elena Tamayo-Mas, Jens Birkholzer et Carlos Jové-Colón. « Phenomenological Model of Nonlinear Dynamics and Deterministic Chaotic Gas Migration in Bentonite : Experimental Evidence and Diagnostic Parameters ». Transport in Porous Media 141, no 2 (janvier 2022) : 585–606. http://dx.doi.org/10.1007/s11242-021-01733-9.
Texte intégralRésumé :
AbstractUnderstanding gas migration in compacted clay materials, e.g., bentonite and claystone, is important for the design and performance assessment of an engineered barrier system of a radioactive waste repository system, as well as many practical applications. Existing field and laboratory data on gas migration processes in low-permeability clay materials demonstrate the complexity of flow and transport processes, including various types of instabilities, caused by nonlinear dynamics of coupled processes of liquid–gas exchange, dilation, fracturing, fracture healing, etc., which cannot be described by classical models of fluid dynamics in porous media. We here show that the complexity of gas migration processes can be explained using a phenomenological concept of nonlinear dynamics and deterministic chaos theory. To do so, we analyzed gas pressure and gas influx (i.e., input) and outflux (i.e., output), recorded during the gas injection experiment in the compact Mx80-D bentonite sample, and calculated a set of the diagnostic parameters of nonlinear dynamics and chaos, such a global embedding dimension, a correlation dimension, an information dimension, and a spectrum of Lyapunov exponents, as well as plotted 2D and 3D pseudo-phase-space strange attractors, based on the univariate influx and outflux time series data. These results indicate the presence of phenomena of low-dimensional deterministic chaotic behavior of gas migration in bentonite. In particular, during the onset of gas influx in the bentonite core, before the breakthrough, the development of gas flow pathways is characterized by the process of chaotic gas diffusion. After the breakthrough, with inlet-to-outlet movement of gas, the prevailing process is chaotic advection. During the final phase of the experiment, with no influx to the sample, the relaxation pattern of gas outflux is resumed back to a process of chaotic diffusion. The types of data analysis and a proposed phenomenological model can be used to establish the basic principles of experimental data-gathering, modeling predictions, and a research design.
19
Liu, Nannan, Binshan Ju, Xinglong Chen, Eric Thompson Brantson, Shuaichen Mu, Yong Yang, Jian Wang et B. M. Mahlalela. « Experimental study of the dynamic mechanism on gas bubbles migration, fragment, coalescence and trapping in a porous media ». Journal of Petroleum Science and Engineering 181 (octobre 2019) : 106192. http://dx.doi.org/10.1016/j.petrol.2019.106192.
Texte intégral
20
Mendonça, Carlos A., Rory Doherty, Nathan D. Amaral, Blathnaid McPolin, Michael J. Larkin et Andrea Ustra. « Resistivity and induced polarization monitoring of biogas combined with microbial ecology at a brownfield site ». Interpretation 3, no 4 (1 novembre 2015) : SAB43—SAB56. http://dx.doi.org/10.1190/int-2015-0057.1.
Texte intégralRésumé :
The accumulation of biogenic greenhouse gases (methane, carbon dioxide) in organic sediments is an important factor in the redevelopment and risk management of many brownfield sites. Good practice with brownfield site characterization requires the identification of free-gas phases and pathways that allow its migration and release at the ground surface. Gas pockets trapped in the subsurface have contrasting properties with the surrounding porous media that favor their detection using geophysical methods. We have developed a case study in which pockets of gas were intercepted with multilevel monitoring wells, and their lateral continuity was monitored over time using resistivity. We have developed a novel interpretation procedure based on Archie’s law to evaluate changes in water and gas content with respect to a mean background medium. We have used induced polarization data to account for errors in applying Archie’s law due to the contribution of surface conductivity effects. Mosaics defined by changes in water saturation allowed the recognition of gas migration and groundwater infiltration routes and the association of gas and groundwater fluxes. The inference on flux patterns was analyzed by taking into account pressure measurements in trapped gas reservoirs and by metagenomic analysis of the microbiological content, which was retrieved from suspended sediments in groundwater sampled in multilevel monitoring wells. A conceptual model combining physical and microbiological subsurface processes suggested that biogas trapped at depth may have the ability to quickly travel to the surface.
21
Amaziane, B., S. Antontsev, L. Pankratov et A. Piatnitski. « Homogenization of Immiscible Compressible Two-Phase Flow in Porous Media : Application to Gas Migration in a Nuclear Waste Repository ». Multiscale Modeling & ; Simulation 8, no 5 (janvier 2010) : 2023–47. http://dx.doi.org/10.1137/100790215.
Texte intégral
22
Smaï, Farid. « A model of multiphase flow and transport in porous media applied to gas migration in underground nuclear waste repository ». Comptes Rendus Mathematique 347, no 9-10 (mai 2009) : 527–32. http://dx.doi.org/10.1016/j.crma.2009.03.011.
Texte intégral
23
Spurin, Catherine, Catherine Callas, Nihal Darraj, Maja Rücker et Sally Benson. « The Importance and Challenges Associated with Multi-scale Heterogeneity for Geological Storage ». InterPore Journal 2, no 1 (26 février 2025) : IPJ260225–2. https://doi.org/10.69631/ipj.v2i1nr76.
Texte intégralRésumé :
Understanding multi-scale heterogeneity in porous media has become increasingly critical as the world transitions from fossil fuel production to geological storage of CO2 and H2 for climate change mitigation. This commentary examines why small-scale heterogeneities have taken on a heightened importance in modeling subsurface fluid migration. We identify three key factors: increased public scrutiny and stricter permitting requirements for storage projects, different risk tolerances requiring long-term monitoring, and distinct flow physics compared to traditional oil and gas extraction. Drawing from current research, we demonstrate how current models consistently underestimate CO2 plume spread, likely due to inadequate representation of small-scale heterogeneities, which will also heavily impact H2 storage in porous rocks. We review the current state of research on incorporating small-scale heterogeneities into field scale models, discuss relevant spatial scales for both CO2 and H2 storage applications, and highlight promising directions for future research in this critical area.
24
Bourgeat, Alain, Mladen Jurak et Farid Smaï. « Two-phase, partially miscible flow and transport modeling in porous media ; application to gas migration in a nuclear waste repository ». Computational Geosciences 13, no 1 (30 août 2008) : 29–42. http://dx.doi.org/10.1007/s10596-008-9102-1.
Texte intégral
25
Li, Xiaofei, Aifen Li, Wanjiang Guo, Shiqi Liu et Shiti Cui. « Experimental Study on Mechanism of Water-Alternating-Gas Injection in thick Sandstone Reservoir ». E3S Web of Conferences 338 (2022) : 01001. http://dx.doi.org/10.1051/e3sconf/202233801001.
Texte intégralRésumé :
For the thick sandstone reservoir, due to gravity differentiation, water drive mainly uses the bottom oil of the reservoir, while gas drive mainly drives the oil along the top of the reservoir. Water-alternating gas (WAG) injection can effectively combine the advantages of water flooding and gas injection, so that gas and water can work in synergy, thus further expanding swept volume and enhancing oil recovery. Over the past half century, the technology has been successfully applied to more than 60 oilfields worldwide, but its mechanism remains to be further studied. In this paper, a total of three tests were conducted through conventional water-flooding (WF), water flooding followed by gas flooding and WAG in sand-packed 2d-model. These experimental processes are recorded by video with time so that the saturation distribution of each phase in porous media can be observed，migration law of gas and water is studied, and the mechanism of WAG displacement is analyzed. The results show that gravity and capillary force have great influence on the process of gas water alternation, thus increasing the overall swept volume of water and gas; The water/gas alternating injection has the highest oil recovery factor (RF) of 75.45% in test 3, in comparison with water flooding followed by gas flooding (70.85% in test 2) and water-flooding (66.7%in test 1); Increase in cycles of WAG tends to reduce residual oil saturation.
26
SHENG, GUANGLONG, YULIANG SU, WENDONG WANG, FARZAM JAVADPOUR et MEIRONG TANG. « APPLICATION OF FRACTAL GEOMETRY IN EVALUATION OF EFFECTIVE STIMULATED RESERVOIR VOLUME IN SHALE GAS RESERVOIRS ». Fractals 25, no 04 (25 juillet 2017) : 1740007. http://dx.doi.org/10.1142/s0218348x17400072.
Texte intégralRésumé :
According to hydraulic-fracturing practices conducted in shale reservoirs, effective stimulated reservoir volume (ESRV) significantly affects the production of hydraulic fractured well. Therefore, estimating ESRV is an important prerequisite for confirming the success of hydraulic fracturing and predicting the production of hydraulic fracturing wells in shale reservoirs. However, ESRV calculation remains a longstanding challenge in hydraulic-fracturing operation. In considering fractal characteristics of the fracture network in stimulated reservoir volume (SRV), this paper introduces a fractal random-fracture-network algorithm for converting the microseismic data into fractal geometry. Five key parameters, including bifurcation direction, generating length ([Formula: see text]), deviation angle ([Formula: see text]), iteration times ([Formula: see text]) and generating rules, are proposed to quantitatively characterize fracture geometry. Furthermore, we introduce an orthogonal-fractures coupled dual-porosity-media representation elementary volume (REV) flow model to predict the volumetric flux of gas in shale reservoirs. On the basis of the migration of adsorbed gas in porous kerogen of REV with different fracture spaces, an ESRV criterion for shale reservoirs with SRV is proposed. Eventually, combining the ESRV criterion and fractal characteristic of a fracture network, we propose a new approach for evaluating ESRV in shale reservoirs. The approach has been used in the Eagle Ford shale gas reservoir, and results show that the fracture space has a measurable influence on migration of adsorbed gas. The fracture network can contribute to enhancement of the absorbed gas recovery ratio when the fracture space is less than 0.2 m. ESRV is evaluated in this paper, and results indicate that the ESRV accounts for 27.87% of the total SRV in shale gas reservoirs. This work is important and timely for evaluating fracturing effect and predicting production of hydraulic fracturing wells in shale reservoirs.
27
TANAKA, Yukihisa. « DEVELOPMENT OF NUMERICAL SIMULATION METHOD FOR GAS MIGRATION THROUGH DENSE BENTONITE USING MODEL OF TWO-PHASE FLOW THROUGH DEFORMABLE POROUS MEDIA ». Doboku Gakkai Ronbunshuu C 66, no 3 (2010) : 530–49. http://dx.doi.org/10.2208/jscejc.66.530.
Texte intégral
28
Smaï, Farid. « Existence of solutions for a model of multiphase flow in porous media applied to gas migration in underground nuclear waste repository ». Applicable Analysis 88, no 10-11 (octobre 2009) : 1609–16. http://dx.doi.org/10.1080/00036810902942226.
Texte intégral
29
Liu, Ning, Lehua Pan et Jianmei Cheng. « Numerical Modeling of CO2 and Brine Leakage through Open Fracture in a Fault Zone : Open Channel Flow or Darcy Flow ». Geofluids 2017 (2017) : 1–21. http://dx.doi.org/10.1155/2017/9035032.
Texte intégralRésumé :
Understanding fluids migration and leakage risk along the fault zone is necessary to guarantee the safety of CO2 geological storage. The validity of Darcy’s law gets challenged in dealing with the flow in open fractures since the occurring of turbulence flow. In this study, we develop a 2D model with usage of T2Well, an integrated wellbore-reservoir simulator, to investigate the leakage problem along open fractures which are embedded in a fault zone from the deep injection reservoir to shallow aquifers. The results record a positive feedback of gas expansion and pressure response in fracture, which causes a quick downward propagation of highly gas saturated zone from the top of fracture and an easy gas breakthrough in the shallower aquifers. The decreasing of aperture size of fracture significantly enhances the leakage rates in fracture, but with less influences as aperture increases. In comparison, the Equivalent Porous Media models show a good approximation with the momentum model of large apertures but poor for the small one. Nevertheless, the differences are small in terms of final CO2 distribution among various aquifers, suggesting that Darcy’s law may be still “effective” in solving flow problem along fractures in a constant injection system at a large time scale.
30
Liu, Yafei, Jingwen Yang, Tianjiang Wu, Yanhong Zhao, Desheng Zhou, Shun Liu et Andrea Brogi. « Pore-Scale Investigation on the Plugging Behavior of Submicron-Sized Microspheres for Heterogeneous Porous Media with Higher Permeability ». Geofluids 2020 (18 août 2020) : 1–9. http://dx.doi.org/10.1155/2020/8869760.
Texte intégralRésumé :
Reservoir heterogeneity is regarded as one of the main reasons leading to low oil recovery for both conventional and unconventional reservoirs. High-permeability layers or fractures could result in ineffective water or gas injection and generate nonuniform profile. Polymer microspheres have been widely applied for the conformance control to overcome the bypass of injected fluids and improve the sweep efficiency. For the purpose of examining the plugging performance of submicron-sized microspheres in high-permeability porous media, systematic investigations were implemented incorporating macroscale blocking rate tests using core samples and pore-scale water migration analysis via nuclear magnetic resonance (NMR). Experimental results indicate that microsphere particle size dominates the plugging performance among three studied factors and core permeability has the least influence on the plugging performance. Subsequently, microsphere flooding was conducted to investigate its oil recovery capability. Different oil recovery behaviors were observed for cores with different permeability. For cores with lower permeability, oil recovery increased stepwise with microsphere injection whereas for higher permeability cores oil recovery rapidly increased and reached a plateau. This experimental work provides a better understanding on the plugging behavior of microspheres and could be employed as a reference for screening and optimizing the microsphere flooding process for profile control in heterogeneous reservoirs.
31
Двояшкин, Нариман Камилович, Марина Васильевна Белоусова et Рамис Нурутдинович Бурханов. « Nuclear spin-lattice magnetic relaxation of alkanes and water in a porous medium of clay minerals ». Нефтяная провинция, no 2(30) (30 juin 2022) : 61–76. http://dx.doi.org/10.25689/np.2022.2.61-76.
Texte intégralRésumé :
Исследования молекулярной подвижности жидкости в пористых средах связано с необходимостью понимания фундаментальных и практических вопросов. К фундаментальным вопросам относятся геометрические и транспортные характеристики порового пространства, взаимодействие жидкости с поверхностью твердой фазы. С практическими вопросами связаны миграция нефти и газа, влияние глинистости на емкостные и фильтрационные свойства коллекторов, подсчет запасов и добычу нефти, а также ряд других. Метод ядерного магнитного резонанса, в частности, изучение спин-решеточной ядерной магнитной релаксации жидкости в системах жидкость - пористая среда помогает получить ответы на перечисленные вопросы. При этом оказывается возможным иметь сведения как о молекулярном состоянии флюидов, так и о структуре пористой среды. Исходными количественными параметрами в подобных исследованиях являются времена ядерной магнитной релаксации. Как правило, зависимости времен релаксации от характеристик системы имеют сложную, неэкспоненциальную форму и трактуются по-разному различными авторами. Целью работы является выяснение особенностей спин-решеточной релаксации модельных жидкостей в пористых средах глинистых минералов - каолинита и монтмориллонита методом импульсного ядерно-магнитного резонанса. The molecular mobility of liquid in porous media studies are related to understand fundamental and practical issues. Fundamental issues include the pore space geometric and transport characteristics, the interaction between liquid and the solid phase surface. Practical issues include oil and gas migration, the impact of clay on reservoir capacity and permeability, estimation of reserves and oil production, and others. The nuclear magnetic resonance method, in particular, spin-lattice nuclear magnetic relaxation of a liquid in liquid-porous medium systems helps to get answers to the listed questions. Information is obtained on both molecular state of fluids and porous medium structure. The initial quantitative parameters in such studies are the times of nuclear magnetic relaxation. As a rule, the dependencies of relaxation times have a complex, non-exponential form and are interpreted in different ways by different authors. The purpose of the work is clarification the features of spin-lattice relaxation of model liquids in clay minerals porous media - kaolinite and montmorillonite by the method of pulsed nuclear magnetic resonance.
32
Zhang, Weidong, Qingyuan Zhao, Xuhui Guan, Zizhen Wang et Zhiwen Wang. « Experiment and Model of Conductivity Loss of Fracture Due to Fine-Grained Particle Migration and Proppant Embedment ». Energies 15, no 7 (24 mars 2022) : 2359. http://dx.doi.org/10.3390/en15072359.
Texte intégralRésumé :
In weakly cemented reservoirs or coal-bed methane reservoirs, the conductivity of hydraulic fractures always declines after a period of production, which greatly influences gas production. In this paper, a comprehensive model considering fine-grained particle migration and proppant embedment is proposed to give a precise prediction for conductivity decline. Then, an experiment was conducted to simulate this process. A published experiment using coal fines was also tested and simulated. The results indicate that both fine-grained particle migration and proppant embedment have great negative effect on conductivity of fractures in weakly cemented sandstone and coal-bed methane reservoirs. The formulation we proposed matches the experimental data smoothly and can be widely used in the prediction of conductivity decline in weakly cemented sandstone and coal-bed methane reservoirs. In order to discuss the influencing factors of the filtration coefficient in the particle transport model, a porous media network model was established based on the theoretical model. The simulation results show that the filtration coefficient increases with the increase in particle size and/or throat size, and the filtration coefficient increases with the decrease in the fluid velocity. At the same time, it was found that the large larynx did not easily cause particle retention. Large size particles tend to cause particle retention.
33
Zhang, Zhihao, Rui Wu et Changying Zhao. « Pore-Scale Study of Buoyancy-Driven Gas Bubble Migration, Breakup, Trapping, and Coalescence in the Near Injection Region of Liquid Saturated Porous Media ». Industrial & ; Engineering Chemistry Research 60, no 33 (17 août 2021) : 12419–28. http://dx.doi.org/10.1021/acs.iecr.1c01363.
Texte intégral
34
Xu, Zhongyi, Shaohua Gu, Daqian Zeng, Bing Sun et Liang Xue. « Numerical Simulation of Sulfur Deposit with Particle Release ». Energies 13, no 6 (23 mars 2020) : 1522. http://dx.doi.org/10.3390/en13061522.
Texte intégralRésumé :
Sulfur deposition commonly occurs during the development of a high-sulfur gas reservoirs. Due to the high gas flow velocity near the wellbore, some of the deposited sulfur particles re-enter the pores and continue to migrate driven by the high-speed gas flow. The current mathematical model for sulfur deposition ignores the viscosity between particles, rising flow caused by turbulence, and the corresponding research on the release ratio of particles. In order to solve the above problems, firstly, the viscous force and rising force caused by turbulence disturbance are introduced, and the critical release velocity of sulfur particles is derived. Then, a release model of sulfur particles that consider the critical release velocity and release ratio is proposed by combining the probability theory with the hydrodynamics theory. Notably, based on the experimental data, the deposition ratio of sulfur particles and the damage coefficient in the sulfur damage model are determined. Finally, a comprehensive particle migration model considering the deposition and release of sulfur particles is established. The model is then applied to the actual gas wells with visible sulfur deposition that target the Da-wan gas reservoir, and the results show that the model correctly reflects flow transport during the process of sulfur deposition in porous media. In addition, through the numerical simulation experiments, it was found that considering the release of sulfur particles reduces the saturation of sulfur particles within a specific range around the well and improve the reservoir permeability in this range. From the perspective of gas production rate, the release of sulfur particles has a limited effect on the gas production rate, which is mainly due to the sulfur particle release being limited, having only a 5 m range near the wellbore area, and thus the amount of gas flow from the unaffected area is basically unchanged.
35
Amaziane, B., S. Antontsev et L. Pankratov. « Time of complete displacement of an immiscible compressible fluid by water in porous media : Application to gas migration in a deep nuclear waste repository ». Nonlinear Analysis : Real World Applications 13, no 5 (octobre 2012) : 2144–53. http://dx.doi.org/10.1016/j.nonrwa.2012.01.009.
Texte intégral
36
Ortega-Villamagua, Erick, Marco Gudiño-Gomezjurado et Alex Palma-Cando. « Microbiologically Induced Carbonate Precipitation in the Restoration and Conservation of Cultural Heritage Materials ». Molecules 25, no 23 (24 novembre 2020) : 5499. http://dx.doi.org/10.3390/molecules25235499.
Texte intégralRésumé :
Microbiologically induced carbonate precipitation (MICP) is a well-known biogeochemical process that allows the formation of calcium carbonate deposits in the extracellular environment. The high concentration of carbonate and calcium ions on the bacterial surface, which serves as nucleation sites, promotes the calcium carbonate precipitation filling and binding deteriorated materials. Historic buildings and artwork, especially those present in open sites, are susceptible to enhanced weathering resulting from environmental agents, interaction with physical-chemical pollutants, and living organisms, among others. In this work, some published variations of a novel and ecological surface treatment of heritage structures based on MICP are presented and compared. This method has shown to be successful as a restoration, consolidation, and conservation tool for improvement of mechanical properties and prevention of unwanted gas and fluid migration from historical materials. The treatment has revealed best results on porous media matrixes; nevertheless, it can also be applied on soil, marble, concrete, clay, rocks, and limestone. MICP is proposed as a potentially safe and powerful procedure for efficient conservation of worldwide heritage structures.
37
Вирц, Рудольф Александрович. « Осесимметричная задача фильтрации газа в пороупругой среде ». Computational Continuum Mechanics 17, no 4 (13 janvier 2025) : 496–508. https://doi.org/10.7242/1999-6691/2024.17.4.40.
Texte intégralRésumé :
The formulation and solution of the problem of burying carbon dioxide (carbon dioxide) in a poroelastic medium are considered. The model is based on the equations describing the filtration of liquids or gases in deformable porous media, which are a generalization of Muskett Leverett's models of poroelastic media. The assumption that the speed of movement of the solid skeleton of the medium is small made it possible to reduce the system of constitutive equations to two equations so that the effective pressure and porosity can be found. The gas filtration area refers to a rock formation in which an injection well is located at depth, and, on the sides, the formation is confined by impermeable rocks. The top of the formation coincides with the Earth surface and is permeable. The migration of carbon dioxide and its release to the surface occurs due to an increase in porosity at the top of the formation. Based on these assumptions, boundary conditions for the velocities of the gas and solid phases are set and then rewritten in terms of the desired function of the effective pressure of the medium. The resulting initial boundary value problem is solved numerically using a scheme of alternating directions and the fourth-order Runge-Kutta method. A difference scheme and an algorithm for solving the problem are given. The orders of uniform convergence in spatial and temporal variables were determined, and an approximate estimate for the rate of convergence of the numerical solution was obtained. Numerical modeling of several options for injecting carbon dioxide into the formation at different well depths and with different injection rates was carried out. Optimal gas injection conditions for its long-term geological storage were determined.
38
Su, Huanjie, Hailong Wang, Qingfu Li et Wengyan Zhang. « Study on the Strength and Microstructure of Coal Gangue Concrete Using Sulfurized CO2 Composite Gas and Steam Carbon Fixation ». Sustainability 17, no 1 (31 décembre 2024) : 243. https://doi.org/10.3390/su17010243.
Texte intégralRésumé :
Addressing the complex physicochemical properties of coal gangue from typical mining areas in Inner Mongolia, this study focuses on this area’s abundant reserves coupled with the low utilization rate and significant strength variability of ecological slope protection materials. Notably, research on the alkalization–carbonization of coal gangue remains scarce. To bridge this gap, we propose a method leveraging the moisture migration behavior of coal gangue porous media. By utilizing continuous displacement high-temperature steam carbon sequestration enhancement technology, internal moisture is gradually and precisely controlled to induce the formation of high-temperature carbonic acid gas. This process facilitates internal carbon sequestration and effectively locks in the sequestration effect. This approach enables effective loading of sulfurized CO2 composite gases in a reversible manner, achieving passive carbon sequestration driven by moisture migration. Consequently, it enhances the negative carbon content within the aggregates while bolstering their mechanical properties. After alkalization pretreatment with various concentrations and three hours of carbon sequestration, the microhardness of the aggregate surface and transition zone were observed to have increased by 24.3% and 36.4%, respectively. Additionally, the compressive and splitting tensile strengths of coal gangue concrete rose by 4.8 MPa and 0.4 MPa, respectively, while porosity decreased by up to 3.6%, and the proportion of harmful pores dropped from 11.22% to 6.54%. A strong correlation between the proportion of harmless/low-harm pores and strength development was observed. Overall, the high-temperature carbonic acid steam displacement method with sulfurized CO2 composite gases effectively improves the physicochemical properties of coal gangue aggregates and enhances surface activity and hydration in the interface transition zone, meeting the engineering standards for in situ ecological remediation in Inner Mongolia’s mining areas.
39
Kleinknecht, Simon Matthias, Holger Class et Jürgen Braun. « Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media ». Hydrology and Earth System Sciences 21, no 3 (8 mars 2017) : 1381–96. http://dx.doi.org/10.5194/hess-21-1381-2017.
Texte intégralRésumé :
Abstract. Non-aqueous-phase liquid (NAPL) contaminants introduced into the unsaturated zone spread as a liquid phase; however, they can also vaporize and migrate in a gaseous state. Vapor plumes migrate easily and thus pose a potential threat to underlying aquifers. Large-scale column experiments were performed to quantify partitioning processes responsible for the retardation of carbon disulfide (CS2) vapor in partially saturated porous media. The results were compared with a theoretical approach taking into account the partitioning into the aqueous phase as well as adsorption to the solid matrix and to the air–water interface. The experiments were conducted in large, vertical columns (i.d. of 0.109 m) of 2 m length packed with different porous media. A slug of CS2 vapor and the conservative tracer argon was injected at the bottom of the column followed by a nitrogen chase. Different seepage velocities were applied to characterize the transport and to evaluate their impact on retardation. Concentrations of CS2 and argon were measured at the top outlet of the column using two gas chromatographs. The temporal-moment analysis for step input was employed to evaluate concentration breakthrough curves and to quantify dispersion and retardation. The experiments conducted showed a pronounced retardation of CS2 in moist porous media which increased with water saturation. The comparison with an analytical solution helped to identify the relative contributions of partitioning processes to retardation. Thus, the experiments demonstrated that migrating CS2 vapor is retarded as a result of partitioning processes. Moreover, CS2 dissolved in the bulk water is amenable to biodegradation. The first evidence of CS2 decay by biodegradation was found in the experiments. The findings contribute to the understanding of vapor-plume transport in the unsaturated zone and provide valuable experimental data for the transfer to field-like conditions.
40
Wang, Shengwei, Xijian Li, Haiteng Xue, Zhonghui Shen et Liuyu Chen. « Fractal characteristics of shale pore structure and its influence on seepage flow ». Royal Society Open Science 8, no 5 (mai 2021) : 202271. http://dx.doi.org/10.1098/rsos.202271.
Texte intégralRésumé :
The migration law of shale gas has a significant influence on the seepage characteristics of shale, and the flow of the gas is closely related to the pore structure. To explore the influence of shale pore parameters on permeability in different diffusion zones, the pore structure of the shale in the Niutitang Formation in Guizhou, China, was analysed based on liquid nitrogen adsorption experiments and nuclear magnetic resonance experiments. The relationship among fractal dimension, organic carbon content (TOC) and BET-specific surface area was analysed based on the fractal dimension of shale pores calculated using the Frenkel–Halsey–Hill model. Shale permeability was calculated using the Knudsen number ( Kn ) and permeability equation, and the influence of the fractal dimension and porosity in different diffusion zones on shale permeability was analysed. Previous studies have shown that: (i) the pores of shale in the Niutitang Formation, Guizhou are mainly distributed within 1–100 nm, with a small total pore volume per unit mass, average pore diameter, large BET specific surface area and porosity; (ii) fractal dimension has a negative correlation with average pore diameter and TOC content and a quadratic relationship with BET specific surface area; and (iii) permeability has a positive correlation with Kn , porosity and fractal dimension. In the transitional diffusion zone, fractal dimension and porosity have a significant impact on permeability. In the Knudsen diffusion zone, porosity has no obvious effect on permeability. The methodologies and results presented will enable more accurate characterization of the complexity of pore structures of porous media and allow further understanding of the seepage law of shale gas.
41
Buffin, A. J. « WAARRE SANDSTONE DEVELOPMENT WITHIN THE PORT CAMPBELL EMBAYMENT ». APPEA Journal 29, no 1 (1989) : 299. http://dx.doi.org/10.1071/aj88026.
Texte intégralRésumé :
The Late Cretaceous Waarre Formation is recognised as the principal reservoir unit throughout the Port Campbell Embayment, where a number of small gas fields were discovered and developed in the late 1970s and the early and mid- 1980s.The Waarre Formation can be subdivided into four units, identified as Unit A, a basal fining upward sequence; Unit B, a medial siltstone with interbedded calcareous sandstones; Unit C, a coarse- grained porous sandstone (the primary gas reservoir); Unit D, a ferruginous siltstone/sandstone sequence.The Upper Waarre, Units C and D, represents a variety of environments unique to a beach barrier- system, including back- water lagoons, swamps, tidal channels, tidal deltas, and beach sands. The development of an Upper Waarre sandstone- beach- barrier model, the identification of various facies, and the construction of regional palaeogeography leads to an understanding of sedimentary deposition during Waarre times.Recent drilling has shown the Upper Waarre to extend laterally in an easterly direction and, as proposed by the depositional model, development of the prospective Waarre Unit C gas sands in a restricted linear east- west zone.By combining the complex structural history of the Port Campbell Embayment and the resultant structures developed with the depositional model of the Waarre Formation, major migration pathways, and thick (>50 m) overlying seals, exploration throughout the embayment can be directed towards prospective gas reservoirs within the Waarre, Unit C, sandstone bodies.
42
Cai, Mingyu, Yuliang Su, Lei Li, Yongmao Hao et Xiaogang Gao. « CO2-Fluid-Rock Interactions and the Coupled Geomechanical Response during CCUS Processes in Unconventional Reservoirs ». Geofluids 2021 (26 février 2021) : 1–22. http://dx.doi.org/10.1155/2021/6671871.
Texte intégralRésumé :
The difficulty of deploying remaining oil from unconventional reservoirs and the increasing CO2 emissions has prompted researchers to delve into carbon emissions through Carbon Capture, Utilization, and Storage (CCUS) technologies. Under the confinement of nanopore in unconventional formation, CO2 and hydrocarbon molecules show different density distribution from in the bulk phase, which leads to a unique phase state and interface behavior that affects fluid migration. At the same time, mineral reactions, asphaltene deposition, and CO2 pressurization will cause the change of porous media geometry, which will affect the multiphase flow. This review highlights the physical and chemical effects of CO2 injection into unconventional reservoirs containing a large number of micro-nanopores. The interactions between CO2 and in situ fluids and the resulting unique fluid phase behavior, gas-liquid equilibrium calculation, CO2 adsorption/desorption, interfacial tension, and minimum miscible pressure (MMP) are reviewed. The pore structure changes and stress distribution caused by the interactions between CO2, in situ fluids, and rock surface are discussed. The experimental and theoretical approaches of these fluid-fluid and fluid-solid reactions are summarized. Besides, deficiencies in the application and safety assessment of CCUS in unconventional reservoirs are described, which will help improve the design and operation of CCUS.
43
Lönartz, Mara I., Jenna Poonoosamy, Yuankai Yang, Naila Ait-Mouheb, Guido Deissmann et Dirk Bosbach. « Deciphering porosity clogging at barrier interfaces in deep geological repositories for radioactive waste ». Safety of Nuclear Waste Disposal 1 (10 novembre 2021) : 181–82. http://dx.doi.org/10.5194/sand-1-181-2021.
Texte intégralRésumé :
Abstract. The disposal of spent nuclear fuels and high-level radioactive wastes in deep geological repositories represents one of the greatest scientific-technical and societal challenges of our times. Most disposal concepts rely on a multibarrier system, consisting of a combination of engineered materials, geotechnical and geological barriers to provide a safe containment of the radioactive waste to protect humans and the environment against dangers arising from ionizing radiation. A reliable safety assessment of a deep geological repository over assessment time scales of several 100 000 years requires a profound and comprehensive understanding of the complex coupled physical (thermal, hydraulic, mechanical), chemical and biogeochemical (THM/CB) processes that govern the long-term evolution of the repository system. As a result of thermal and chemical gradients at the interfaces of different components and materials of the multi-barrier system (e.g. interfaces between metallic waste containers and bentonite backfill or between structural concrete and clay host rock), mineral dissolution and precipitation reactions are promoted; thus the (local) porosity, the volume filled with gas and/or water, can increase or decrease leading to changes in the macroscopic transport properties of the respective media. Although a reduction of the porosity (porosity clogging) appears to be desirable to inhibit radionuclide migration, it can also be detrimental, particularly in the case of gas pressure build-up due to canister corrosion or bacterial activity. So far, porosity clogging at barrier interfaces and associated consequences on solute or gas transport remain poorly understood; currently used mathematical descriptions of porosity clogging in reactive transport codes usually fail to capture respective experimental observations (Chagneau et al., 2015; Deng et al., 2021). In this context, we are developing a “lab-on-a-chip” set-up, which combines time lapse optical microscopy imaging and in operando Raman spectroscopy (Poonoosamy et al., 2019, 2020) to determine (i) whether complete clogging is possible and permanent, (ii) which parameters control the porosity clogging and (iii) which changes in transport properties of porous media are induced due to porosity clogging. Our approach comprises micronized counterdiffusion experiments with in situ visualization and monitoring of the evolution of mineralogy and microstructure/pore architecture with time. Complementary pore scale modelling will be used to derive key relationships that describe changes in transport properties due to mineral precipitation-induced porosity clogging. This approach will help to improve reactive transport codes and their predictive capabilities thus enhancing confidence and reduce uncertainties in long-term predictions, leading to more realistic descriptions of the evolution of complex repository systems.
44
Narayanaswamy, Ganesh, Mukul M. Sharma et G. A. Pope. « Effect of Heterogeneity on the Non-Darcy Flow Coefficient ». SPE Reservoir Evaluation & ; Engineering 2, no 03 (1 juin 1999) : 296–302. http://dx.doi.org/10.2118/56881-pa.
Texte intégralRésumé :
Summary An analytical method for calculating an effective non-Darcy flow coefficient for a heterogeneous formation is presented. The method presented here can be used to calculate an effective non-Darcy flow coefficient for heterogeneous gridblocks in reservoir simulators. Based on this method, it is shown that the non-Darcy flow coefficient of a heterogeneous formation is larger than the non-Darcy flow coefficient of an equivalent homogenous formation. Non-Darcy flow coefficients calculated from gas well data show that non-Darcy flow coefficients obtained from well tests are significantly larger than those predicted from experimental correlations. Permeability heterogeneity is a very likely reason for the differences in non-Darcy flow coefficients often seen between laboratory and field data. Introduction In this paper, we present an analytical method for calculating an effective non-Darcy flow coefficient for a heterogeneous reservoir. The effect of heterogeneity on the non-Darcy flow coefficient is also shown using numerical simulations. Non-Darcy flow coefficients calculated from the analysis of welltest data from a gas condensate field are compared with experimental correlations. Such a comparison allows us to more accurately assess the importance of non-Darcy flow in gas condensate reservoirs. Literature Review As early as 1901, Reynolds observed, in his classical experiments of injecting dye into water flowing through glass tubes, that after some high flowrate, flow rate was no longer proportional to the pressure drop. Forchheimer1 also observed this phenomena and proposed the following quadratic equation to express the relationship between pressure drop and velocity in a porous medium: d P d r = μ k u + β ρ u 2 . ( 1 ) This equation has come to be known asForchheimer's equation. At low Reynolds number (creeping flow conditions), the above equation reduces to Darcy's law. Tek2 developed a generalized Darcy equation in dimensionless form which predicts the pressure drop with good agreement over all ranges of Reynolds numbers. Katz et al.3 attributed the phenomenon of non-Darcy flow to turbulence. Tek et al.4 proposed the following correlation for?: β = 5.5 × 10 9 k 5 / 4 ϕ 3 / 4 . ( 2 ) Gewers and Nichol5 conducted experiments on microvugular carbonate cores to measure the non-Darcy flow coefficient. They also studied the effect of the presence of a second static fluid phase and the effect on plugging due to fines migration. They found that ? decreases and then increases with liquid saturation. Wong6 studied the effect of a mobile liquid saturation on ?. He used distilled water as the liquid phase and water saturated nitrogen as the gas phase on the same cores used by Gewers and Nichol. He plotted ? vs liquid saturation and found that there is an eight-fold increase in ? when the liquid saturation increases from 40% to 70%. He concluded that ? can be approximately calculated from the dry core experiments by using the effective gas permeability. Geertsma7,8 introduced an empirical relationship between ?,k and ? based on a combination of experimental data and dimensional analysis. He noted that the observed departure from Darcy's law was due to the convective acceleration and deceleration of the fluid particles. He also defined a new Reynolds number as ?k??/?, and suggested the following correlation for ? with a constant C (k is in ft 2, ?is in 1/ft). β = C k 0.5 ϕ 5.5 . ( 3 ) For the case of gas flowing through a core with a static liquid phase, he suggested the following correlation: β = C ( k k r g ) 0.5 [ ϕ ( 1 − S w ) ] 5.5 . ( 4 ) Phipps and Khalil9 proposed a method for determining the exponent in a Forchheimer-type equation. Firoozabadi and Katz10 presented are view of the theory of high velocity gas flow through porous media. Evanset al.11 reviewed the various correlations. They conducted an experimental study of the effect of the immobile liquid saturation and suggested a correlation based on dimensional analysis. Nguyen12performed an experimental study of non-Darcy flow through perforations on a synthetic core using air. These experiments showed that non-Darcy flow exists in the convergence zone and the perforation tunnel. Results of this study showed that Darcy flow equations can over predict well productivity by as much as 100%. Jones13 conducted experiments on 355 sandstone and 29 limestone cores. These tests were done for various core types: vuggy limestones, crystalline limestones, and fine grained sandstones. He presented the following correlation: β = 6.15 × 10 10 k − 1.55 . ( 5 ) He also points out that the group ?k? which is the characteristic length used for defining a Reynolds number for porous media, should be proportional to the characteristic length k/ϕ. He developed an approximate multilayer flow model that demonstrates that the departure from the above relation is due to permeability variations. Jones suggested that heterogeneity may be the reason why all correlations involving ? exhibit so much scatter.
45
Löffelholz, Marco, Jens Osiewacz, Lydia Weseler et Thomas Turek. « How the Choice of Electrolyte Affects the Carbon Efficiency in Electrochemical CO2 Reduction at Silver Gas Diffusion Electrodes ». ECS Meeting Abstracts MA2023-01, no 26 (28 août 2023) : 1701. http://dx.doi.org/10.1149/ma2023-01261701mtgabs.
Texte intégralRésumé :
Reducing CO2 emissions by replacing fossil fuels with renewable energy sources is an important step in the context of climate change. Electrochemical CO2 reduction is a promising technology for supporting this shift, since it provides the possibility to store electrical energy in form of high value chemicals while consuming CO2. It is now generally accepted that the use of gas diffusion electrodes (GDEs) is beneficial due to the limited solubility of CO2 in water [1]. To achieve a better understanding of the complex processes taking place in the electrode, the description by a mathematical model is desirable. We present a TFFA (thin-film flooded agglomerate) model for silver GDEs based on the approach presented by Franzen et al. [2] for the oxygen reduction reaction. The model describes the processes in the GDE, including reaction, diffusion, and migration. Therefore, the model provides an in-depth view on the local reaction environment in the electrode, which becomes highly alkaline at elevated current densities due to the formation of hydroxide ions by the electrochemical reactions [3]. This causes the rate of bicarbonate/carbonate formation to exceed the rate of electrochemical CO2 reduction, resulting in a limited carbon efficiency [4]. Using acidic electrolytes might significantly reduce this limitation by decreasing the local alkalinity. This has already been experimentally demonstrated for gold electrodes using electrolytes with pH values in the range of 2-4 [5]. In this study, we present experimental results for silver GDEs using acidic electrolytes. These results show that the carbon efficiency can be increased while maintaining a similar Faradaic efficiency as obtained for KHCO3 electrolytes at industrially relevant current densities. Our model calculations support these findings and give insights about the development of the local pH in dependence of the applied current density for different pH values of the bulk electrolyte. [1] T. Burdyny, W. A. Smith, CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions, Energy & Environmental Science 12 (5) (2019), 1442-1453. [2] D. Franzen, M. C. Paulisch, B. Ellendorff, I. Manke, T. Turek, Spatially resolved model of oxygen reduction reaction in silver-based porous gas-diffusion electrodes based on operando measurements, Electrochimica Acta 375 (2021), 137976. [3] M. Löffelholz, J. Osiewacz, A. Lüken, K. Perrey, A. Bulan, T. Turek, Modeling electrochemical CO2 reduction at silver gas diffusion electrodes using a TFFA approach. Chemical Engineering Journal 435(2) (2022), 134920. [4] J. A. Rabinowitz, M.W. Kanan, The future of low-temperature carbon dioxide electrolysis depends on solving one basic problem. Nature Communications 11 (2020), 5231. [5] M.C.O. Monteiro, M.F. Philips, K.J.P. Schouten et al., Efficiency and selectivity of CO2 reduction to CO on gold gas diffusion electrodes in acidic media. Nature Communication 12 (2021), 4943. Figure 1
46
Gianni, Eleni, Pavlos Tyrologou, Dounya Behnous, Márton Pál Farkas, Paula Fernández-Canteli Álvarez, Jesús García Crespo, Ricardo Chacartegui Ramirez, Nikolaos Koukouzas et Júlio Carneiro. « CO2 sequestration potential in Depleted Hydrocarbon fields – A geochemical approach ». Open Research Europe 5 (20 janvier 2025) : 17. https://doi.org/10.12688/openreseurope.19280.1.
Texte intégralRésumé :
Background The CO2 emissions reduction is crucial for the energy transition. Thus, new technologies for CO2 capture and storage are under development, such as CEEGS 1,2 . Porous media and rock caverns are geological formations of high interest for such technology. Among them, depleted hydrocarbon fields (DHF) gain ground due to the experience of reservoir characterisation, sealing performance, storage operability, and already established infrastructure which critically decreases the cost. However, one of the major problems caused during CO2 storage in DHF is the interactions between the injected CO2 and the remaining fluids. Methods In this study, the potential CO2 storage in DHF was investigated. Marismas 3 was used as a hypothetical model area for the examination of CO2 interactions with a carbonate-silisiclastic reservoir. PHREEQC software 1 was used to investigate reservoir rock/water/remained gas (CH4) interactions followed by interactions taking place after the CO2 injection. Different scenarios were used for the CO2 concentration and behaviour in the reservoir. To make the system more complex and generic, the CMG-GEM software 3 was utilized to examine the long-term sequestration of CO2 through dissolution trapping, residual trapping, and lateral migration in a reservoir analogue to the Marismas field, but at higher depth, compatible with the CEEGS technology. Results During the CO2 injection, carbonic acid was formed, causing a dissolution of several minerals, leading to siderite and clay minerals precipitation (e.g. kaolinite, Ca-montmorillonite, and illite), which may cause problems to the permeability of the system. The colloidal nature of siderite and the Ca-montmorillonite swelling properties are of high concern for pore throat clogging. However, the other newly formed mineralogical phases are not threatening the reservoir quality. CMG-GEM validated the critical phase of CO2 plume establishment. Conclusions The proposed DHF is promising for real-world underground applications fitting to CEEGS technology.
47
Assilbekov, Bakhytzhan K., Nurlykhan Ye Kalzhanov, Darezhat A. Bolysbek, Kenboy Sh Uzbekaliyev, Bakbergen Ye Bekbau et Alibek B. Kuljabekov. « Study of the efficiency of machine learning algorithms based on data of various rocks ». Kazakhstan journal for oil & ; gas industry 5, no 3 (22 janvier 2024) : 5–19. http://dx.doi.org/10.54859/kjogi108649.
Texte intégralRésumé :
Background: Absolute permeability plays an important role in studying the fluids flow in porous media during the development of oil and gas reservoirs, the injection of CO2 into reservoirs for storage, the monitoring of pollutants migration in underground aquifers, and the modeling of catalytic systems. Therefore, an accurate and fast evaluation of its values is an important task.
Aim: The purpose of this article is to study the applicability of machine learning methods for predicting the absolute permeability of carbonate samples, as well as ways to improve the prediction of permeability.
Materials and methods: The input data is 408 small volumes extracted from four cylindrical carbonate samples composed almost entirely of calcite. Input data includes total and connected porosity, specific surface area, radii of all and only connected pores, coordination number, throat radius and length, tortuosity, and absolute permeability. Permeability prediction is carried out using regression machine learning methods such as random forest, extremely random trees and extended gradient boosting. Parameters (data) of small volumes were determined using pore-scale modeling of water flow in their pore space applying a specialized Avizo software.
Results: Data of small volumes extracted from fractured and non-fractured samples were analyzed, and the results showed that there are good relationships between many parameters of small volumes. For example, the connected and total porosity have a second-order polynomial relationship with a high correlation coefficient. Using the above-mentioned regression machine learning methods, absolute permeability values were predicted when input data divided into training and testing data in a ratio of 80/20 and 70/30.
Conclusion: Using the logarithm of permeability instead of permeability itself and considering fractured and non-fractured samples separately, can increase the accuracy of absolute permeability prediction using the above-mentioned machine learning methods up to 90%. The extremely random trees method is the most accurate among the three machine learning methods considered for our task.
48
Sharma, M. M., et Y. C. Yortsos. « Fines migration in porous media ». AIChE Journal 33, no 10 (octobre 1987) : 1654–62. http://dx.doi.org/10.1002/aic.690331009.
Texte intégral
49
Wang, Ruihe, Zhangxin Chen, Jishun Qin et Ming Zhao. « Performance of Drainage Experiments With Orinoco Belt Heavy Oil in a Long Laboratory Core in Simulated Reservoir Conditions ». SPE Journal 13, no 04 (1 décembre 2008) : 474–79. http://dx.doi.org/10.2118/104377-pa.
Texte intégralRésumé :
Summary When some heavy-oil reservoirs are produced using gas drive, they show three important features: low production gas/oil ratios, higher-than-expected production rates, and relatively high oil recovery. The mechanism for this unusual behavior remains controversial and poorly understood, though the term "foamy oil" is often used to describe such behavior. The impetus for this work stems from some recent projects performed in the Orinoco belt, Venezuela. There exist nearly one trillion bbl of heavy oil (oil in place) in this region on the basis of a recent evaluation. Two crucial issues must be addressed before or during designing production projects: What is a suitable method for evaluating the foamy-oil drive mechanism that plays a major role during such oil recovery, and how do we obtain a reasonable percentage of ultimate oil recovery? Unfortunately, it is still difficult to give good explanations for these two issues, although several studies were performed. This paper attempts to present better explanations for these two issues using experimental drainage in a long laboratory core in simulated reservoir conditions. Our experiments show that ultimate oil recovery for the heavy oil in the Orinoco belt can be as high as 15-20%. This high recovery comes from three contributions: fluid and rock expansion, foamy-oil drive, and conventional-solution-gas drive. Approximately 3-5% of recovery is from fluid and rock expansion, 11-16% from foamy-oil drive, and 2-4% from conventional-solution-gas drive. This ultimate-oil-recovery percentage is much higher than the 12% that has been used in the field-development plan for the Orimulsion project. The experiments performed and their findings obtained in this paper are representative at least in the Orinoco belt region. Introduction Most practitioners try to produce as much oil as possible under primary recovery. In all solution-gas-drive reservoirs, gas is released from solution as the reservoir pressure declines. Gas initially exists in the form of small bubbles created within individual pores. As time evolves and pressure continues to decline, these bubbles grow to occupy the pores. With a further decline in pressure, the bubbles created in different locations become large enough to coalesce into a continuous gas phase. Conventional wisdom indicates that the discrete bubbles that are larger than pore throats remain immobile (trapped by capillary forces) and that gas flows only after the bubbles have coalesced into a continuous gas phase. Once the gas phase becomes continuous, which is equivalent to the gas saturation becoming larger than critical, the minimum saturation at which a continuous gas phase exists in porous media (Chen et al. 2006), traditional two-phase (gas and oil) flow with classical relative permeabilities occurs. A result of this evolution process is that the production gas/oil ratio (GOR) increases rapidly after the critical gas saturation has been exceeded. Field observations in some heavy-oil reservoirs, however, do not fit into this solution-gas-drive description in that the production GOR remains relatively low. The recovery factors (percentage of the oil in a reservoir that can be recovered) in such reservoirs are also unexpectedly high. A simple explanation of these observations could be that the critical gas saturation is high in these reservoirs. This explanation cannot be confirmed by direct laboratory measurement of the critical gas saturation. An alternative explanation of the observed GOR behavior is that gas, instead of flowing only as a continuous phase, also flows in the form of gas-in-oil dispersion. This type of dispersed gas/oil flow is what is referred to as "foamy-oil" flow. Although the unusual production behavior in some heavy-oil reservoirs was observed as early as the late 1960s, Smith (1988) appears to have been the first to report it and used the terms "oil/gas combination" and "mixed fluid" to describe the mixture of oil and gas that is entrained in heavy oil as very tiny bubbles. Baibakov and Garushev (1989) used the term "viscous-elastic system" to describe highly viscous oil with very fine bubbles present. Sarma and Maini (1992) were the first to use the phrase "foamy oil" to describe viscous oil that contains dispersed gas bubbles. Claridge and Prats (1995) used the terms "foamy heavy oil" and "foamy crude." Although there is continuing debate on the suitability of the term "foamy-oil flow" to describe the anomalous flow of the oil/gas mixture in primary production of heavy oil (Firoozabadi 2001; Tang and Firoozabadi 2003; Tang and Firoozabadi 2005), this expression has become a fixture in the petroleum-engineering terminology (Chen 2006, Maini 1996). The actual structure of foamy-oil flow and its mathematical description are still not well understood. Much of the earlier discussion of such flow was based on the concept of microbubbles [i.e., bubbles much smaller than the average pore-throat size and, thus, free to move with the oil during flow (Sheng et al. 1999)]. This type of dispersion can be produced only by nucleation of a very large number of bubbles (explosive nucleation) and by the presence of a mechanism that prevents these bubbles from growing into larger bubbles with decline in pressure (Maini 1996). This hypothesis has not been supported by experimental evidence. A more plausible hypothesis on the structure of foamy-oil flow is that it involves much larger bubbles migrating with the oil and that the dispersion is created by the breakup of bubbles during their migration with the oil. The major difference between the conventional-solution-gas drive and the foamy-solution-gas drive is that the pressure gradient in the latter is strong enough to mobilize gas clusters after they have grown to a certain size. Maini (1999) presented experimental evidence that supports this hypothesis for foamy-oil flow. This hypothesis seems consistent with the visual observations in micromodels that show the bubble size to be larger than the pore size. However, more laboratory experiments must be conducted to validate this hypothesis. The impetus for this work stems from some recent projects performed in the Orinoco belt, Venezuela. The largest heavy-oil reserves in the world are in this region, with nearly one trillion bbbl of heavy oil in place on the basis of a recent evaluation (Fig. 1) (Andarcia et al. 2001). The unusual recovery performance mentioned previously has been observed during drainage of heavy-oil reservoirs in the Orinoco belt. The problems we now face are the following. How will we estimate the production performance for the present project by taking into account the foamy-oil-drive mechanism? In addition, what will be an applicable measure to evaluate the production potential of this project? What will a production profile of this project look like? How much oil will be produced within a certain time period of our operation? Unfortunately, there were no satisfactory answers yet for these questions. This paper attempts to address these issues using results from a suite of laboratory experiments. The attempts to address these issues will improve our understanding of foamy-oil behavior and its mechanism.
50
ZHENG, JIAYI, XING SHI, JUAN SHI et ZHENQIAN CHEN. « PORE STRUCTURE RECONSTRUCTION AND MOISTURE MIGRATION IN POROUS MEDIA ». Fractals 22, no 03 (septembre 2014) : 1440007. http://dx.doi.org/10.1142/s0218348x14400076.
Texte intégralRésumé :
Three kinds of porous media (isotropic, perpendicular anisotropic and parallel anisotropic porous media) with the same porosity, different pore size distributions and fractal spectral dimensions were reconstructed by random growth method. It was aimed to theoretically study the impact of microscopic pore structure on water vapor diffusion process in porous media. The results show that pore size distribution can only denote the static characteristics of porous media but cannot effectively reflect the dynamic transport characteristics of porous media. Fractal spectral dimension can effectively analyze and reflect pores connectivity and moisture dynamic transport properties of porous media from the microscopic perspective. The pores connectivity and water vapor diffusion performance in pores of porous media get better with the increase of fractal spectral dimension of porous media. Fractal spectral dimension of parallel anisotropic porous media is more than that of perpendicular anisotropic porous media. Fractal spectral dimension of isotropic porous media is between parallel anisotropic porous media and perpendicular anisotropic porous media. Other macroscopic parameters such as equilibrium diffusion coefficient of water vapor, water vapor concentration variation at right boundary in equilibrium, the time when water vapor diffusion process reaches a stable state also can characterize the pores connectivity and water vapor diffusion properties of porous media.