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1
Fam, M., and J. C. Santamarina. "Coupled diffusionfabric-flow phenomena: an effective stress analysis." Canadian Geotechnical Journal 33, no. 3 (July 2, 1996): 515–22. http://dx.doi.org/10.1139/t96-074.
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Concentration diffusion, fluid flow and fabric changes are coupled phenomena in fine soils. Indeed, experimental results previously presented by the authors showed the presence of a pressure front advancing ahead of the diffusing high-concentration front in bentonite and kaolinite specimens. This note presents a simple analysis of diffusionfabric-flow coupling, based on elementary double-layer repulsion and attraction. Model predictions adequately agree with experimental data. High specific surface, high initial void ratio, and low initial pore-fluide concentration increase the sensitivity of soils to changes in pore-fluid concentration and enhance the potential development of pore pressure fronts. Key words: coupling, diffusion, clay, pore pressure, interparticle forces.
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Bhattacharya, Pathikrit, and Robert C. Viesca. "Fluid-induced aseismic fault slip outpaces pore-fluid migration." Science 364, no. 6439 (May 2, 2019): 464–68. http://dx.doi.org/10.1126/science.aaw7354.
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Earthquake swarms attributed to subsurface fluid injection are usually assumed to occur on faults destabilized by increased pore-fluid pressures. However, fluid injection could also activate aseismic slip, which might outpace pore-fluid migration and transmit earthquake-triggering stress changes beyond the fluid-pressurized region. We tested this theoretical prediction against data derived from fluid-injection experiments that activated and measured slow, aseismic slip on preexisting, shallow faults. We found that the pore pressure and slip history imply a fault whose strength is the product of a slip-weakening friction coefficient and the local effective normal stress. Using a coupled shear-rupture model, we derived constraints on the hydromechanical parameters of the actively deforming fault. The inferred aseismic rupture front propagates faster and to larger distances than the diffusion of pressurized pore fluid.
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Sakaguchi, H., and H. B. Mühlhaus. "Hybrid Modelling of Coupled Pore Fluid-solid Deformation Problems." Pure and Applied Geophysics 157, no. 11 (December 2000): 1889–904. http://dx.doi.org/10.1007/pl00001066.
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Hoffman, Monty, and James Crafton. "Multiphase flow in oil and gas reservoirs." Mountain Geologist 54, no. 1 (January 2017): 5–14. http://dx.doi.org/10.31582/rmag.mg.54.1.5.
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The porous rocks that make up oil and gas reservoirs are composed of complex combinations of pores, pore throats, and fractures. Pore networks are groups of these void spaces that are connected by pathways that have the same fluid entry pressures. Any fluid movement in pore networks will be along the pathways that require the minimum energy expenditure. After emplacement of hydrocarbons in a reservoir, fluid saturations, capillary pressure, and energy are in equilibrium, a significant amount of the reservoir energy is stored at the interface between the fluids. Any mechanism that changes the pressure, volume, chemistry, or temperature of the fluids in the reservoir results in a state of energy non-equilibrium. Existing reservoir engineering equations do not address this non-equilibrium condition, but rather assume that all reservoirs are in equilibrium. The assumption of equilibrium results in incorrect descriptions of fluid flow in energy non-equilibrium reservoirs. This, coupled with the fact that drilling-induced permeability damage is common in these reservoirs, often results in incorrect conclusions regarding the potential producibility of the well. Relative permeability damage, damage that can change which fluids are produced from a hydrocarbon reservoir, can occur even in very permeable reservoirs. Use of dependent variables in reservoir analysis does not correctly describe the physics of fluid flow in the reservoir and will lead to potentially incorrect answers regarding producibility of the reservoir.
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Jeon, Min-Kyung, Amin Hosseini Zadeh, Seunghee Kim, and Tae-Hyuk Kwon. "Fluid-driven mechanical responses of deformable porous media during two-phase flows: Hele-Shaw experiments and hydro-mechanically coupled pore network modeling." E3S Web of Conferences 205 (2020): 08009. http://dx.doi.org/10.1051/e3sconf/202020508009.
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Injecting fluid into a porous material can cause deformation of the pore structure. This hydro-mechanically coupled (i.e., poromechanical) phenomenon plays an essential role in many geological and biological operations across a wide range of scales, from geologic carbon storage, enhanced oil recovery and hydraulic fracturing to the transport of fluids through living cells and tissues, and to fuel cells. In this study, we conducted an experimental and numerical investigation of the hydro-mechanical coupling during fluid flows in porous media at the fundamental pore-scale. First, experimental demonstrations were undertaken to ascertain the effect of the hydro-mechanical coupling for two-phase fluid flows in either deformable or non-deformable porous media. Next, a hydro-mechanically coupled pore network model (HM-PNM) was employed to test a various range of influential parameters. The HM-PNM results were consistent with the experimental observations, including the advancing patterns of fluids and the development of the poroelastic deformation, when the viscous drop was incorporated. The hydro-mechanical coupling was observed to reduce the inlet pressure required to maintain a constant flow rate, whereas its effect on the pattern of fluid flow was minimal. The interfacial tension alteration also changed the pressure and deformation. The viscosity of invading fluid showed significant effects on both the patterns of fluid displacement and mechanical deformation.
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Zienkiewicz, O. C., Maosong Huang, Jie Wu, and Shiming Wu. "A New Algorithm for the Coupled Soil–Pore Fluid Problem." Shock and Vibration 1, no. 1 (1993): 3–14. http://dx.doi.org/10.1155/1993/801536.
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Two new semiexplicit algorithms for the coupled soil–pore fluid problem are developed in this article. The stability of the new algorithms is much better than that of the previous algorithm. The first new scheme (H*-scheme) based on operator splitting before spatial discretization can avoid the restriction of mixed formulation in the incompressible (zero permeability) limit. The steady-state formulation is discussed to verify this argument. Several examples illustrate the article.
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Das, Vishal, Tapan Mukerji, and Gary Mavko. "Numerical simulation of coupled fluid-solid interaction at the pore scale: A digital rock-physics technology." GEOPHYSICS 84, no. 4 (July 1, 2019): WA71—WA81. http://dx.doi.org/10.1190/geo2018-0488.1.
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We have used numerical modeling to capture the physics related to coupled fluid-solid interaction (FSI) and the frequency dependence of pore scale fluid flow in response to pore pressure heterogeneities at the pore scale. First, we perform numerical simulations on a simple 2D geometry consisting of a pair of connected cracks to benchmark the numerical method. We then compute and contrast the stresses and pore pressures obtained from our numerical method with the commonly used method that considers only structural mechanics, ignoring FSI. Our results demonstrate that the stresses and pore pressures of these two cases are similar for low frequencies (1 Hz). However, at higher frequencies (1 kHz), we observe pore-pressure heterogeneities from the FSI numerical method that cannot be representatively modeled using the structural mechanics approach. At even higher frequencies (100 MHz), scattering effects in the fluid give rise to higher pressure heterogeneities in the pore space. The dynamic effective P-wave modulus [Formula: see text], attenuation [Formula: see text], and P-wave velocity [Formula: see text] were calculated using the results obtained from the numerical simulations. These results indicate a shift in the dispersion curves toward lower frequencies when the fluid viscosity is increased or when the aspect ratio of the microcrack is decreased. We then applied the numerical method on a 3D digital rock sample of Berea sandstone for a sweep of frequencies ranging from 10 Hz to 100 MHz. The calculated pore pressure at the low frequency (1 kHz) is homogeneous and the fluid is in a relaxed state, whereas at the high frequency (100 kHz), the pore pressure is heterogeneous, and the fluid is in an unrelaxed state. This type of numerical method helps in modeling and understanding the dynamic effects of fluid at different frequencies that result in velocity dispersion and attenuation.
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Daley, T. M., M. A. Schoenberg, J. Rutqvist, and K. T. Nihei. "Fractured reservoirs: An analysis of coupled elastodynamic and permeability changes from pore-pressure variation." GEOPHYSICS 71, no. 5 (September 2006): O33—O41. http://dx.doi.org/10.1190/1.2231108.
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Equivalent-medium theories can describe the elastic compliance and fluid-permeability tensors of a layer containing closely spaced parallel fractures embedded in an isotropic background. We propose a relationship between effective stress (background or lithostatic stress minus pore pressure) and both permeability and elastic constants. This relationship uses an exponential-decay function that captures the expected asymptotic behavior, i.e., low effective stress gives high elastic compliance and high fluid permeability, while high effective stress gives low elastic compliance and low fluid permeability. The exponential-decay constants are estimated for physically realistic conditions. With relationships coupling pore pressure to permeability and elastic constants, we are able to couple hydromechanical and elastodynamic modeling codes. A specific coupled simulation is demonstrated where fluid injection in a fractured reservoir causes spatially and temporally varying changes in pore pressure, permeability, and elastic constants. These elastic constants are used in a 3D finite-difference code to demonstrate time-lapse seismic monitoring with different acquisition geometries. Changes in amplitude and traveltime are seen in surface seismic P-to-S reflections as a function of offset and azimuth, as well as in vertical seismic profile P-to-S reflections and in crosswell converted S-waves. These observed changes in the seismic response demonstrate seismic monitoring of fluid injection in the fractured reservoir.
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Sadeghi, Mohammad, Hamed Sadeghi, and Clarence E. Choi. "A lattice Boltzmann study of dynamic immiscible displacement mechanisms in pore doublets." MATEC Web of Conferences 337 (2021): 02011. http://dx.doi.org/10.1051/matecconf/202133702011.
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An advanced chromodynamics, Rothmann-Keller (RK) type lattice Boltzmann model (LBM) is used in this study. The new model benefits from high stability and capability of independently setting the interfacial tension of the fluids as an input parameter. In addition, the model is coupled with a wall-density approach to simulate the hydrophilic or hydrophobic properties of wall surfaces. Finally, injection of a wetting (non-wetting) fluid in a pore doublet geometry which is initially filled with non-wetting (wetting) fluid is simulated. The results of simulation reveal the capability of RK-LBM to simulate relative permeabilities of fluids in porous media for future studies of two-immiscible phase flow in various geoenvironmental problems.
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WANG, FUYONG, ZHICHAO LIU, LIANG JIAO, CONGLE WANG, and HU GUO. "A FRACTAL PERMEABILITY MODEL COUPLING BOUNDARY-LAYER EFFECT FOR TIGHT OIL RESERVOIRS." Fractals 25, no. 05 (September 4, 2017): 1750042. http://dx.doi.org/10.1142/s0218348x17500426.
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A fractal permeability model coupling non-flowing boundary-layer effect for tight oil reservoirs was proposed. Firstly, pore structures of tight formations were characterized with fractal theory. Then, with the empirical equation of boundary-layer thickness, Hagen–Poiseuille equation and fractal theory, a fractal torturous capillary tube model coupled with boundary-layer effect was developed, and verified with experimental data. Finally, the parameters influencing effective liquid permeability were quantitatively investigated. The research results show that effective liquid permeability of tight formations is not only decided by pore structures, but also affected by boundary-layer distributions, and effective liquid permeability is the function of fluid type, fluid viscosity, pressure gradient, fractal dimension, tortuosity fractal dimension, minimum pore radius and maximum pore radius. For the tight formations dominated with nanoscale pores, boundary-layer effect can significantly reduce effective liquid permeability, especially under low pressure gradient.
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Wong, H., X. S. Zhang, C. J. Leo, and T. A. Bui. "Internal Erosion of Earth Structures as a Coupled Hydromechanical Process." Applied Mechanics and Materials 330 (June 2013): 1084–89. http://dx.doi.org/10.4028/www.scientific.net/amm.330.1084.
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The present paper describes a model of internal erosion of earth structures based on rigorous thermodynamic principles and the theory of porous media. The focus is concerned with the initial stage of internal erosion, prior to the formation of macroscopic channels, whenthe continuum approach is applicable. The soil skeleton saturated by a pore fluid is treated as the superposition of 3 continua in interaction ;the pore fluid itself consists of a mixture of water and eroded particles. The erosion kinetics is based on the shear stress developed at the solid-fluid interface. The applicability of the model is illustrated by a finite element simulation. The simulations show how the phenomenon of piping preferentially arises in regions where hydraulic gradients are critical. Effects of mechanical degradations due to internal erosion are demonstrated.
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Gutierrez, M., R. W. Lewis, and I. Masters. "Petroleum Reservoir Simulation Coupling Fluid Flow and Geomechanics." SPE Reservoir Evaluation & Engineering 4, no. 03 (June 1, 2001): 164–72. http://dx.doi.org/10.2118/72095-pa.
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Summary This paper presents a discussion of the issues related to the interaction between rock deformation and multiphase fluid flow behavior in hydrocarbon reservoirs. Pore-pressure and temperature changes resulting from production and fluid injection can induce rock deformations, which should be accounted for in reservoir modeling. Deformation can affect the permeability and pore compressibility of the reservoir rock. In turn, the pore pressures will vary owing to changes in the pore volume. This paper presents the formulation of Biot's equations for multiphase fluid flow in deformable porous media. Based on this formulation, it is argued that rock deformation and multiphase fluid flow are fully coupled processes that should be accounted for simultaneously, and can only be decoupled for predefined simple loading conditions. In general, it is shown that reservoir simulators neglect or simplify important geomechanical aspects that can impact reservoir productivity. This is attributed to the fact that the only rock mechanical parameter involved in reservoir simulations is pore compressibility. This parameter is shown to be insufficient in representing aspects of rock behavior such as stress-path dependency and dilatancy, which require a full tensorial constitutive relation. Furthermore, the pore-pressure changes caused by the applied loads from nonpay rock and the influence of nonpay rock on reservoir deformability cannot be accounted for simply by adjusting the pore compressibility. Introduction In the last two decades, there has been a strong emphasis on the importance of geomechanics in several petroleum engineering activities such as drilling, borehole stability, hydraulic fracturing, and production-induced compaction and subsidence. In these areas, in-situ stresses and rock deformations, in addition to fluid-flow behavior, are key parameters. The interaction between geomechanics and multiphase fluid flow is widely recognized in hydraulic fracturing. For instance, Advani et al.1 and Settari et al.2 have shown the importance of fracture-induced in-situ stress changes and deformations on reservoir behavior and how hydraulic fracturing can be coupled with reservoir simulators. However, in other applications, geomechanics, if not entirely neglected, is still treated as a separate aspect from multiphase fluid flow. By treating the two fields as separate issues, the tendency for each field is to simplify and make approximate assumptions for the other field. This is expected because of the complexity of treating geomechanics and multiphase fluid flow as coupled processes. Recently, there has been a growing interest in the importance of geomechanics in reservoir simulation, particularly in the case of heavy oil or bituminous sand reservoirs,3,4 water injection in fractured and heterogeneous reservoirs,5–7 and compacting and subsiding fields.8,9 Several approaches have been proposed to implement geomechanical effects into reservoir simulation. The approaches differ on the elements of geomechanics that should be implemented and the degree to which these elements are coupled to multiphase fluid flow. The objective of this paper is to illustrate the importance of geomechanics on multiphase flow behavior in hydrocarbon reservoirs. An extension of Biot's theory10 for 3D consolidation in porous media to multiphase fluids, which was proposed by Lewis and Sukirman,11 will be reviewed and used to clarify the issues involved in coupling fluid flow and rock deformation in reservoir simulators. It will be shown that for reservoirs with relatively deformable rock, fluid flow and reservoir deformation are fully coupled processes, and that such coupled behaviors cannot be represented sufficiently by a pore-compressibility parameter alone, as is done in reservoir simulators. The finite-element implementation of the fully coupled equations and the application of the finite-element models to an example problem are presented to illustrate the importance of coupling rock deformation and fluid flow. Multiphase Fluid Flow in Deformable Porous Media Fig. 1 illustrates the main parameters involved in the flow of multiphase fluids in deformable porous media and how these parameters ideally interact. The main quantities required to predict fluid movement and productivity in a reservoir are the fluid pressures (and temperatures, in case of nonisothermal problems). Fluid pressures also partly carry the loads, which are transmitted by the surrounding rock (particularly the overburden) to the reservoir. A change in fluid pressure will change the effective stresses following Terzaghi's12 effective stress principle and cause the reservoir rock to deform (additional deformations are induced by temperature changes in nonisothermal problems). These interactions suggest two types of fluid flow and rock deformation coupling:Stress-permeability coupling, where the changes in pore structure caused by rock deformation affect permeability and fluid flow.Deformation-fluid pressure coupling, where the rock deformation affects fluid pressure and vice versa. The nature of these couplings, specifically the second type, are discussed in detail in the next section. Stress-Permeability Coupling This type of coupling is one where stress changes modify the pore structure and the permeability of the reservoir rock. A common approach is to assume that the permeability is dependent on porosity, as in the Carman-Kozeny relation commonly used in basin simulators. Because porosity is dependent on effective stresses, permeability is effectively stress-dependent. Another important effect, in addition to the change in the magnitude of permeability, is on the change in directionality of fluid flow. This is the case for rocks with anisotropic permeabilities, where the full permeability tensor can be modified by the deformation of the rock. Examples of stress-dependent reservoir modeling are given by Koutsabeloulis et al.6 and Gutierrez and Makurat.7 In both examples, the main aim of the coupling is to account for the effects of in-situ stress changes on fractured reservoir rock permeability, which in turn affect the fluid pressures and the stress field. The motivation for the model comes from the field studies done by Heffer et al.5 showing that there is a strong correlation between the orientation of the principal in-situ stresses with the directionality of flow in fractured reservoirs during water injection. There is also growing evidence that the earth's crust is generally in a metastable state, where most faults and fractures are critically stressed and are on the verge of further slip.13 This situation will broaden the range of cases with strong potential for coupling of fluid flow and deformation.
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Zheng, Binshuang, Xiaoming Huang, Jingwen Ma, Zhengqiang Hong, Jiaying Chen, Runmin Zhao, and Shengze Zhu. "Evaluation on Distribution Characteristics of Pore Water Pressure within Saturated Pavement Structure Based on the Proposed Tire-Fluid-Pavement Coupling Model." Advances in Materials Science and Engineering 2022 (January 28, 2022): 1–12. http://dx.doi.org/10.1155/2022/5849418.
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To investigate the flow characteristics of pore water in asphalt pavement and the variation law of the pore water pressure under vehicle loading, a novel method based on BA network and quartet structure generation set method was proposed to reconstruct the three-dimensional (3D) pavement model with pores. The permeability coefficient and the gradation curve were adopted to evaluate the reliability and stability of the random growth pavement model. Then, the tire-fluid-pavement coupling model was established with FLUENT 3D based on the fluid Mie–Gruneisen state equation. According to the built fluid-solid coupling model, the pressure-velocity coupled finite volume algorithm was applied to study the distribution of the pore water pressure in asphalt pavement. Results show that the pore water pressure in asphalt pavement decays periodically with time under vehicle loading. For different types of asphalt pavement, the pore water pressure in open-graded friction course (OGFC) pavement is the smallest during the whole process. Moreover, the peak values of the pore water pressure decrease in the order of asphalt concrete (AC) pavement, stone mastic asphalt (SMA) pavement, and OGFC pavement. The maximum negative value of the pore water pressure is generally less than 0.3 times the maximum positive values. As for saturated pavement pores, the pore water pressure is hardly affected by the water film thickness. The positive peak value of the pore water pressure increases on an approximate parabolic curve as the vehicle speed improves gradually, while the negative one remains largely unchanged. The results are expected to help reduce tire hydroplaning risk and provide guidance for the selection of asphalt mixtures of drainage asphalt pavement.
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Cheng, Hongyang, Stefan Luding, Jens Harting, and Vanessa Magnanimo. "Direct numerical simulation of wave propagation in saturated random granular packings using coupled LBM-DEM." EPJ Web of Conferences 249 (2021): 14003. http://dx.doi.org/10.1051/epjconf/202124914003.
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Poroelasticity theory predicts wave velocities in a saturated porous medium through a coupling between the bulk deformation of the solid skeleton and porous fluid flow. The challenge emerges below the characteristic wavelengths at which hydrodynamic interactions between grains and pore fluid become important. We investigate the pressure and volume fraction dependence of compressional- and shear-wave velocities in fluid-saturated, random, isotropic, frictional granular packings. The lattice Boltzmann method (LBM) and discrete element method (DEM) are two-way coupled to capture the particle-pore fluid interactions; an acoustic source is implemented to insert a traveling wave from the fluid reservoir to the saturated medium. We extract wave velocities from the acoustic branches in the wavenumber-frequency space, for a range of confining pressures and volume fractions. For random isotropic granular media the pressure-wave velocity data collapse on a single curve when scaled properly by the volume fraction.
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Wang, He, Rui Wang, and Jian-Min Zhang. "Solid-Fluid Coupled Numerical Analysis of Suction Caisson Installation in Sand." Journal of Marine Science and Engineering 9, no. 7 (June 26, 2021): 704. http://dx.doi.org/10.3390/jmse9070704.
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Suction caissons are widely used foundations in offshore engineering. The change in excess pore pressure and seepage field caused by penetration and suction significantly affects the soil resistance around the caisson wall and tip, and also affects the deformation of the soil within and adjacent to the caisson. This study uses Arbitrary Lagrangian–Eulerian (ALE) large deformation solid-fluid coupled FEM to investigate the changes in suction pressure and the seepage field during the process of the suction caisson installation in sand. A nonlinear Drucker-Prager model is used to model soil, while Coulomb friction is applied at the soil-caisson interface. The ALE solid-fluid coupled FEM is shown to be able to successfully simulate both jacked penetration and suction penetration caisson installation processes in sand observed in centrifuge tests. The difference in penetration resistance for jacked and suction installation is found to be caused by the seepage and excess pore pressure generated during the suction caisson installation, highlighting the importance of using solid-fluid coupled effective stress-based analysis to consider seepage in the evaluation of suction caisson penetration.
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Cao, Rui Lang, Shao Hui He, Fang Wang, and Fa Lin Qi. "Stability Analysis of Large Underground Station Based on Coupled Fluid-Solid Theorem." Advanced Materials Research 748 (August 2013): 1104–8. http://dx.doi.org/10.4028/www.scientific.net/amr.748.1104.
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Tunnelling may disturb the intrinsic balance of a stratum, and result in accidents like caving or gushing. In order to assess the security of underground station project, numerical analysis for the stability of surrounding rock was done with fast Lagrangian analysis of continua in three dimensions (FLAC3D), Multiple factors were considered, including surrounding rock classes, tunnel depths, groundwater tables, construction methods and initial supporting systems. According to the results of principal stresses, displacements, plastic zones, pore pressure distribution and the mechanical characters of supporting system including anchors and shotcrete, the seepage mechanism of underground station has been discussed. The pore pressure distribution of deep-buried tunnel was studied as well. The study results can provide a theoretical basis for the design of tunnel and underground works in aquifer strata.
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Dean, Rick H., Xiuli Gai, Charles M. Stone, and Susan E. Minkoff. "A Comparison of Techniques for Coupling Porous Flow and Geomechanics." SPE Journal 11, no. 01 (March 1, 2006): 132–40. http://dx.doi.org/10.2118/79709-pa.
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Summary This paper compares three techniques for coupling multiphase porous flow and geomechanics. Sample simulations are presented to highlight the similarities and differences in the techniques. One technique uses an explicit algorithm to couple porous flow and displacements in which flow calculations are performed every timestep and displacements are calculated only during selected timesteps. A second technique uses an iteratively coupled algorithm in which flow calculations and displacement calculations are performed sequentially for the nonlinear iterations during each timestep. The third technique uses a fully coupled approach in which the program's linear solver must solve simultaneously for fluid flow variables and displacement variables. The techniques for coupling porous flow with displacements are described and comparison problems are presented for single-phase and three-phase flow problems involving poroelastic deformations. All problems in this paper are described in detail, so the results presented here may be used for comparison with other geomechanical/porous-flow simulators. Introduction Many applications in the petroleum industry require both an understanding of the porous flow of reservoir fluids and an understanding of reservoir stresses and displacements. Examples of such processes include subsidence, compaction drive, wellbore stability, sand production, cavity generation, high-pressure breakdown, well surging, thermal fracturing, fault activation, and reservoir failure involving pore collapse or solids disposal. It would be useful to compare porous flow/geomechanics techniques for all of these processes, because some of these processes involve a stronger coupling between porous flow and geomechanics than others. However, this paper looks at a subset of these processes and compares three coupling techniques for problems involving subsidence and compaction drive. All of the sample problems presented in this paper assume that the reservoir absolute permeabilities are constant during a run. Displacements influence fluid flow through the calculation of pore volumes, and fluid pressures enter the displacement calculations through the poroelastic constitutive equations. Several authors have presented formulations for modeling poroelastic, multiphase flow. Settari and Walters (1999) discuss the different methods that have been used to combine poroelastic calculations with porous flow calculations. They categorize these different methods of coupling poroelastic calculations with porous flow calculations as decoupled (Minkoff et al. 1999a), explicitly coupled, iteratively coupled, and fully coupled. The techniques discussed in this paper are explicitly coupled, iteratively coupled, and fully coupled.
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Han, Xu, Shangxu Wang, Genyang Tang, Chunhui Dong, Yanxiao He, Tao Liu, Liming Zhao, and Chao Sun. "Coupled effects of pressure and frequency on velocities of tight sandstones saturated with fluids: measurements and rock physics modelling." Geophysical Journal International 226, no. 2 (May 5, 2021): 1308–21. http://dx.doi.org/10.1093/gji/ggab157.
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SUMMARY Elastic moduli and velocities of tight sandstones are strongly influenced by rock-frame heterogeneity, pore microstructure and fluid in addition to pressure and probing-wave frequency. The effects of pressure and frequency on the elastic moduli and velocities are different from those of conventional sandstones with high porosity and high permeability due to complexity of pore microstructure. To investigate these effects, we measured two tight sandstone samples for their velocities in the dry and fluid saturation conditions using the ultrasonic transmission technique and the low-frequency stress–strain method. The variations in the ultrasonic velocities with pressure see a transition from non-linear to linear increase for the dry samples, in contrast to a gradual increase for the fluid-saturated samples. The low frequency velocities of the saturated sample T1 and T2 directly show significant dispersion in a wide range of frequencies (1–100 Hz), and the magnitudes of the dispersion are suppressed by the pressure. The low-frequency velocities also increase with pressure, showing increasing trends bounded by the ultrasonic velocity–pressure curves for the dry and fluid saturation conditions. An elaborate rock physics model, considering a discrete aspect ratio spectrum and the simple squirt flow model, was constructed to account for the pressure and frequency dependence of the velocities. The predictions from the modified squirt flow model can fit well the measured velocities at varying pressures, both in the low-frequency range and the ultrasonic frequency range. The real measurements and the modelling results suggest that the pressure- and frequency-dependence cannot be modelled without considering such aspect ratio spectra. The effects of pressure and frequency are coupled in that they are interconnected by the microstructure of the pores. Changes in the pressure and fluid saturation (and thus wave frequency) both contribute to stiffening of the rock frame, and they both strongly depend on the presence of microcracks in the rock. Therefore, this rock physics model could be applied in extraction of pore microstructure and fluid properties provided elastic moduli or velocities can be estimated accurately.
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Akanji, Lateef T., Adamu Ibrahim, Hossein Hamidi, Stephan Matthai, and Alfred Akisanya. "A New Explicit Sequentially Coupled Technique for Chemo-Thermo-Poromechanical Modelling and Simulation in Shale Formations." Energies 16, no. 3 (February 3, 2023): 1543. http://dx.doi.org/10.3390/en16031543.
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A new explicit sequentially coupled technique for chemo-thermo-poromechanical problems in shale formations is developed. Simultaneously solving the flow and geomechanics equations in a single step is computationally expensive with consequent limitations on the computations involving well or reservoir-scale geometries. The newly developed solution sequence involves solving the temperature field within the porous system. This is followed by the computation of the chemical activity constrained by the previously computed temperature field. The pore pressure is then computed by coupling the pore thermal and chemical effects but without consideration of the volumetric strains. The geomechanical effect of the volumetric strain, stress tensors, and associated displacement vectors on the pore fluid is subsequently computed explicitly in a single-step post-processing operation. By increasing the borehole pressure to 20 MPa, it is observed that the rock displacement and velocities concurrently increase by 50%. However, increasing the wellbore temperature and chemical activities shows only a slight effect on the rock and pore fluid. In the chemo-thermo-poroelasticity steady-state simulation, the maximum displacements recorded in the Hmin and Hmax are 0.00633 m and 0.0035 m, respectively, for 2D and 0.21 for the 3D simulation. In the transient simulation, the displacement values are observed to increase gradually over time with a corresponding decrease in the maximum pore-fluid velocity. A comparison of this work and the partial two-way coupling scheme in a commercial simulator for the 2D test cases was carried out. The maximum differences between the computed temperatures, displacement values, and fluid velocities are 0.33%, 0.7%, and 0%, respectively. The analysed results, therefore, indicate that this technique is comparatively accurate and more computationally efficient than running a full or partial two-way coupling scheme.
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Konovalenko, Ig S., E. V. Shilko, and Iv S. Konovalenko. "The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete." PNRPU Mechanics Bulletin, no. 2 (December 15, 2020): 37–51. http://dx.doi.org/10.15593/perm.mech/2020.2.04.
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Many infrastructural concrete facilities, such as dams, bridge footings, foundations of port facilities and offshore drilling platforms, operate in a permanent contact with water. The permeable fractured-porous structure of concrete determines the water-saturated state of the surface layers of such concrete elements. Under dynamic contact loading, the pore fluid is capable of exerting a significant mechanical influence on the local stress-strain state and strength characteristics of the surface layers of concrete. This has to be taken into account when assessing the wear intensity of surface layers and predicting a concrete element’s service life. The aforesaid determines the relevance of the study aimed at identifying the influence of the pore fluid and characteristics of the concrete pore structure on the strength and fracture pattern under quasistatic and dynamic compressive loading. The present work is devoted to the theoretical study and generalization of the laws of mechanical influence of the pore fluid on the dynamic strength of high-strength concrete with a two-scale pore structure. The emphasis in the study is on analyzing the contributions of each of the pore subsystems to the integral mechanical effect of the fluid. To carry out such an analysis, a coupled hydromechanical model is developed. It takes into account the compositional structure of concrete, the presence of a pore space in a cement stone of two different scales, the interaction of a pore liquid and a solid-phase skeleton based on the Bio poroelasticity model, as well as fluid filtration in a pore space. By using the developed model were performed the numerical studies of the dependence between the compressive strength of the representative concrete volumes of the mesoscopic scale on the strain rate, the sample size, the pore fluid viscosity, and pore structure parameters. The simulation results showed the possibility of combining the obtained dependencies into a generalized (master) curve in terms of a combined dimensionless parameter, which has the meaning similar to the Darcy number. We identified two key factors that control the type and parameters of the concrete master curve of the dynamic strength. The first factor is the mobility of the pore fluid in the network of the capillary pores. It determines the rate of stress equalization in the porous skeleton due to fluid flow. The second factor is the interconnection of large micropores with the network of the small capillary pore channels. It determines the magnitude of the decrease in stress concentration in micropores by filtering the excess pore fluid into the capillary pore network. It is shown that the contributions of these two factors to the amplitude of variation of the dynamic strength of the water-saturated concrete are additive, and their total contribution reaches 25 %.
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Selvadurai, A. P. S., and A. P. Suvorov. "Boundary heating of poro-elastic and poro-elasto-plastic spheres." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2145 (May 10, 2012): 2779–806. http://dx.doi.org/10.1098/rspa.2012.0035.
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This paper examines the coupled hydro-thermo-mechanical behaviour of a fluid-saturated porous sphere with a skeletal fabric that can exhibit either elastic or elasto-plastic mechanical behaviour. Analytical results for the thermo-poro-elastic response of the sphere subjected to transient heat transfer are complemented by computational results for the analogous thermo-poro-elasto-plastic problem. The results presented in the paper examine the influence of the permeability, thermal expansion properties of the pore fluid and the skeleton, and the elasto-plasticity effects of the porous skeleton on the time-dependent pore fluid pressure, displacement and stress within the sphere.
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Niu, Ben, and Samuel Krevor. "The Impact of Mineral Dissolution on Drainage Relative Permeability and Residual Trapping in Two Carbonate Rocks." Transport in Porous Media 131, no. 2 (November 22, 2019): 363–80. http://dx.doi.org/10.1007/s11242-019-01345-4.
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AbstractCarbon dioxide injection into deep saline aquifers is governed by a number of physico-chemical processes including mineral dissolution and precipitation, multiphase fluid flow, and capillary trapping. These processes can be coupled; however, the impact of fluid–rock reaction on the multiphase flow properties is difficult to study and is not simply correlated with variations in porosity. We observed the impact of rock mineral dissolution on multiphase flow properties in two carbonate rocks with distinct pore structures. Observations of steady-state $$\hbox {N}_2$$N2–water relative permeability and residual trapping were obtained, along with mercury injection capillary pressure characteristics. These tests alternated with eight stages in which 0.5% of the mineral volume was uniformly dissolved into solution from the rock cores using an aqueous solution with a temperature-controlled acid. Variations in the multiphase flow properties did not relate simply to changes in porosity, but corresponded to the changes in the underlying pore structure. In the Ketton carbonate, dissolution resulted in an increase in the fraction of pore volume made up by the smallest pores and a decrease in the fraction made up by the largest pores. This resulted in an increase in the relative permeability to the nonwetting phase, a decrease in the relative permeability to the wetting phase, and a modest, but systematic decrease in residual trapping. In the Estaillades carbonate, dissolution resulted in an increase in the fraction of pore volume made up by pores in the central range of the initial pore size distribution, and a corresponding decrease in the fraction made up by both the smallest and largest pores. This resulted in a decrease in the relative permeability to both the wetting and nonwetting fluid phases and no discernible impact on the residual trapping. In summary, the impact of rock matrix dissolution will be strongly dependent on the impact of that dissolution on the underlying pore structure of the rock. However, if the variation in pore structure can be observed or estimated with modelling, then it should be possible to estimate the impacts on multiphase flow properties.
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Wang, Rongjiang, and Hans‐Joachim Kümpel. "Poroelasticity: Efficient modeling of strongly coupled, slow deformation processes in a multilayered half‐space." GEOPHYSICS 68, no. 2 (March 2003): 705–17. http://dx.doi.org/10.1190/1.1567241.
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We present a fast, powerful numerical scheme to compute poroelastic solutions for excess pore pressure and displacements in a multilayered half‐space. The solutions are based on the mirror‐image technique and use an extension of Haskell's propagator method. They can be applied to assess in‐situ formation parameters from the surface deformation field when fluids are injected into or extracted from a subsurface reservoir, or they can be used to simulate changes in pore‐fluid pressure resulting from matrix displacements induced by an earthquake. The performance of the numerical scheme is tested through comparison with observations of the surface deformation as recorded by tiltmeters in the vicinity of an iteratively pumped well. Modeling of near‐surface tilt data around a productive well is useful in constraining hydraulic diffusivity in the layered subsurface.
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Buscarnera, Giuseppe, Yanni Chen, José Lizárraga, and Ruiguo Zhang. "Multi‐scale simulation of rock compaction through breakage models with microstructure evolution." Proceedings of the International Association of Hydrological Sciences 382 (April 22, 2020): 421–25. http://dx.doi.org/10.5194/piahs-382-421-2020.
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Abstract. Regional subsidence due to fluid depletion includes the interaction among multiple physical processes. Specifically, rock compaction is governed by coupled hydro-mechanical feedbacks involving fluid flow, effective stress change and pore collapse. Although poroelastic models are often used to explain the delay between depletion and subsidence, recent evidence indicates that inelastic effects could alter the rock microstructure, thus exacerbating coupling effects. Here, a constitutive law built within the framework of Breakage Mechanics is proposed to account for the inherent connection between rock microstructure, hydraulic conductivity, and pore compaction. Furthermore, it is embedded into a 1-D hydromechanical coupled finite element analysis (FEA) to explore the effects of micro-structure rearrangement on the development of reservoir compaction. Numerical examples with the proposed model are compared with simulations under constant hydraulic conductivity to illustrate the model capability to capture the non-linear processes of reservoir compaction induced by fluid depletion.
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Jia, Shanpo, Caoxuan Wen, Fucheng Deng, Chuanliang Yan, and Zhiqiang Xiao. "Coupled THM Modelling of Wellbore Stability with Drilling Unloading, Fluid Flow, and Thermal Effects Considered." Mathematical Problems in Engineering 2019 (April 9, 2019): 1–20. http://dx.doi.org/10.1155/2019/5481098.
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Both overbalanced drilling and underbalanced drilling will lead to the change of pore pressure around wellbore. Existing research is generally based on hydraulic-mechanical (HM) coupling and assumes that pore pressure near the wellbore is initial formation pressure, which has great limitations. According to the coupled theory of mixtures for rock medium, a coupled thermal-hydraulic-mechanical (THM) model is proposed and derived, which is coded with MATLAB language and ABAQUS software as the solver. Then the wellbore stability is simulated with the proposed model by considering the drilling unloading, fluid flow, and thermal effects between the borehole and the formation. The effect of field coupling on pore pressure, stress redistribution, and temperature around a wellbore has been analyzed in detail. Through the study of wellbore stability in different conditions, it is found that (1) for overbalanced drilling, borehole with impermeable wall is more stable than that of ones with permeable wall and its stability can be improved by reducing the permeable ability of the wellbore wall; (2) for underbalanced drilling, the stability condition of permeable wellbore is much higher than that of impermeable wellbore; (3) the temperature has important influence on wellbore stability due to the variation of pore pressure and thermal stress; the wellbore stability can be improved with cooling drilling fluid for deep well. The present method can provide references for coupled thermal-hydraulic-mechanical-chemical (THMC) process analysis for wellbore.
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Meng, Chunfang, and Michael Fehler. "The role of geomechanical modeling in the measurement and understanding of geophysical data collected during carbon sequestration." Leading Edge 40, no. 6 (June 2021): 413–17. http://dx.doi.org/10.1190/tle40060413.1.
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As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.
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Huang, Maosong, and O. C. Zienkiewicz. "New unconditionally stable staggered solution procedures for coupled soil-pore fluid dynamic problems." International Journal for Numerical Methods in Engineering 43, no. 6 (November 30, 1998): 1029–52. http://dx.doi.org/10.1002/(sici)1097-0207(19981130)43:6<1029::aid-nme459>3.0.co;2-h.
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Hua, Leina. "Stable element-free Galerkin solution procedures for the coupled soil-pore fluid problem." International Journal for Numerical Methods in Engineering 86, no. 8 (December 29, 2010): 1000–1026. http://dx.doi.org/10.1002/nme.3087.
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Cai, Mingyu, Yuliang Su, Lei Li, Yongmao Hao, and Xiaogang Gao. "CO2-Fluid-Rock Interactions and the Coupled Geomechanical Response during CCUS Processes in Unconventional Reservoirs." Geofluids 2021 (February 26, 2021): 1–22. http://dx.doi.org/10.1155/2021/6671871.
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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.
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Liu, Xuemei, and Zichen Deng. "Generalized Multi-Symplectic Numerical Implementation of Dynamic Responses for Saturated Poroelastic Timoshenko Beam." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 38, no. 4 (August 2020): 774–83. http://dx.doi.org/10.1051/jnwpu/20203840774.
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Based on the porous media theory and Timoshenko beam theory, properties of dynamic responses in fluid-solid coupled incompressible saturated poroelastic Timoshenko beam are investigated by generalized multi-symplectic method. Dynamic response equation set of incompressible saturated poroelastic Timoshenko beam is presented at first. Then a first order generalized multi-symplectic form of this dynamic response equation set is constructed, and errors of generalized multi-symplectic conservation law, generalized multi-symplectic local momentum and generalized multi-symplectic local energy are also derived. A Preissmann Box generalized multi-symplectic scheme of the dynamic response equation set is presented, the discrete errors of generalized multi-symplectic conservation law, generalized multi-symplectic local momentum conservation law and generalized multi-symplectic local energy conservation law are also obtained. In view of the dynamic responses of incompressible saturated poroelastic Timoshenko cantilever beam with two ends permeable and free end subjected to the step load, the transverse dynamic response process of the solid skeleton is simulated numerically, the evolution processes of solid effective stress and the equivalent moment of the pore fluid pressure over time are also presented numerically. The effects of fluid-solid coupled interaction parameter and slenderness ratio of the beam on the solid dynamic response process are revealed, as well as the effects on all generalized multi-symplectic numerical errors are checked simultaneously. From results obtained, the processes for solid deflection, solid effective stress and the equivalent moment of the pore fluid pressure approaching to their steady response values are all shortened with increasing of fluid-solid coupled interaction parameter, while the response process of solid deflection and the pore fluid equivalent moment are lengthened with increasing of slenderness ratio of the beam. Moreover, the steady value of solid deflection is much closer to the static deflection value of classic single phase elastic Euler-Bernoulli beam with increasing of the slenderness ratio. As time goes on, the solid skeleton of the beam will support all outside load, so equivalent moment of the pore fluid pressure becomes zero at last. In addition, it is presented all generalized multi-symplectic numerical errors decrease with the decreasing of parameters representing the dissipation effect for the dynamic system.
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Hu, Jun, and Xu Ling Xu. "Fully Coupled Dynamic Analysis of Earth and Rock-Filled Dam." Applied Mechanics and Materials 71-78 (July 2011): 3292–96. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.3292.
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The coupled 3D Dynamic Mechanical/Fluid is performed for the Nuozhadu earth and rock-filled dam by FLAC3D, but literature on the fully coupled of fluid-solid under earthquake is not too much. This paper gives a good example of applying FLAC3D to do the fully coupled simulation, and after a system in mechanical and fluid is got, the dynamic simulation can be done. A more accurate estimation of pore water pressure and the distribution of acceleration and irrecoverable displacement of the dam under dynamic are obtained. The result shows that permanent displacement would occur in the potential slide mass of the slope under earthquake. Finally the method to improve the slope stability is suggested. The results provide important references to the design.
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WANG, FUYONG, ZHICHAO LIU, JIANCHAO CAI, and JIAN GAO. "A FRACTAL MODEL FOR LOW-VELOCITY NON-DARCY FLOW IN TIGHT OIL RESERVOIRS CONSIDERING BOUNDARY-LAYER EFFECT." Fractals 26, no. 05 (October 2018): 1850077. http://dx.doi.org/10.1142/s0218348x18500779.
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Flow in nanoscale pore-throats of tight oil reservoirs is strongly affected by boundary-layers, and exhibits low-velocity non-Darcy flow phenomena. The relationship between flow velocity and pressure gradient is highly nonlinear and difficult to be modeled mathematically. This paper proposed a low-velocity non-Darcy flow model which can account for boundary-layer effect in tight oil reservoirs. First, a modified Hagen–Poiseuille equation coupled with boundary-layer effect in a single capillary tube was derived. Then, assuming pores in tight formations following fractal distribution, an analytical expression of nonlinear correlation between flow velocity and pressure gradient in fractal porous media was developed. Finally, the proposed model was validated with experiment data, and parameters influencing low-velocity non-Darcy flow were quantitatively evaluated. The research results show that the decreasing boundary-layer thickness with the increase pressure gradient is the main reason of low-velocity non-Darcy flow in tight oil reservoirs. Our model can effectively describe the nonlinear relationship between flow velocity and pressure gradient. The relationship between threshold pressure gradient (TPG) and pseudo threshold pressure gradient (PTPG) can also be predicted using our model. Fluid viscosity has great impact on nonlinear flow behavior, and with fluid viscosity increasing TPG and PTPG increase significantly. TPG is the function of fluid type, fluid viscosity and maximum pore diameter, and decreases exponentially with the increasing maximum pore size.
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Kolbjørnsen, Odd, Arild Buland, Ragnar Hauge, Per Røe, Abel Onana Ndingwan, and Eyvind Aker. "Bayesian seismic inversion for stratigraphic horizon, lithology, and fluid prediction." GEOPHYSICS 85, no. 3 (March 25, 2020): R207—R221. http://dx.doi.org/10.1190/geo2019-0170.1.
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We have developed an efficient methodology for Bayesian prediction of lithology and pore fluid, and layer-bounding horizons, in which we include and use spatial geologic prior knowledge such as vertical ordering of stratigraphic layers, possible lithologies and fluids within each stratigraphic layer, and layer thicknesses. The solution includes probabilities for lithologies and fluids and horizons and their associated uncertainties. The computational cost related to the inversion of large-scale, spatially coupled models is a severe challenge. Our approach is to evaluate all possible lithology and fluid configurations within a local neighborhood around each sample point and combine these into a consistent result for the complete trace. We use a one-step nonstationary Markov prior model for lithology and fluid probabilities. This enables prediction of horizon times, which we couple laterally to decrease the uncertainty. We have tested the algorithm on a synthetic case, in which we compare the inverted lithology and fluid probabilities to results from other algorithms. We have also run the algorithm on a real case, in which we find that we can make high-resolution predictions of horizons, even for horizons within tuning distance from each other. The methodology gives accurate predictions and has a performance making it suitable for full-field inversions.
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Hanowski, Katja K., and Oliver Sander. "The hydromechanical equilibrium state of poroelastic media with a static fracture: A dimension-reduced model with existence results in weighted Sobolev spaces and simulations with an XFEM discretization." Mathematical Models and Methods in Applied Sciences 28, no. 13 (December 6, 2018): 2511–56. http://dx.doi.org/10.1142/s0218202518500549.
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We introduce a coupled system of partial differential equations for the modeling of the fluid–fluid and fluid–solid interactions in a poroelastic material with a single static fracture. The fluid flow in the fracture is modeled by a lower-dimensional Darcy equation, which interacts with the surrounding rock matrix and the fluid it contains. We explicitly allow the fracture to end within the domain, and the fracture width is an unknown of the problem. The resulting weak problem is nonlinear, elliptic and symmetric, and can be given the structure of a fixed-point problem. We show that the coupled fluid–fluid problem has a solution in a specially crafted Sobolev space, even though the fracture width cannot be bounded away from zero near the crack tip. For numerical simulations, we combine XFEM discretizations for the rock matrix deformation and pore pressure with a standard lower-dimensional finite element method for the fracture flow problem. The resulting coupled discrete system consists of linear subdomain problems coupled by nonlinear coupling conditions. We solve the coupled system with a substructuring solver and observe very fast convergence. We also observe optimal mesh dependence of the discretization errors even in the presence of crack tips.
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Nguyen, Vinh X., and Youname N. Abousleiman. "Incorporating electrokinetic effects in the porochemoelastic inclined wellbore formulation and solution." Anais da Academia Brasileira de Ciências 82, no. 1 (March 2010): 195–222. http://dx.doi.org/10.1590/s0001-37652010000100015.
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The porochemoelectroelastic analytical models and solutions have been used to describe the response of chemically active and electrically charged saturated porous media such as clays, shales, and biological tissues. However, these attempts have been restricted to one-dimensional consolidation problems, which are very limited in practice and not general enough to serve as benchmark solutions for numerical validation. This work summarizes the general linear porochemoelectroelastic formulation and presents the solution of an inclined wellbore drilled in a fluid-saturated chemically active and ionized formation, such as shale, and subjected to a three-dimensional in-situ state of stress. The analytical solution to this geometry incorporates the coupled solid deformation and simultaneous fluid/ion flows induced by the combined influences of pore pressure, chemical potential, and electrical potential gradients under isothermal conditions. The formation pore fluid is modeled as an electrolyte solution comprised of a solvent and one type of dissolved cation and anion. The analytical approach also integrates into the solution the quantitative use of the cation exchange capacity (CEC) commonly obtained from laboratory measurements on shale samples. The results for stresses and pore pressure distributions due to the coupled electrochemical effects are illustrated and plotted in the vicinity of the inclined wellbore and compared with the classical porochemoelastic and poroelastic solutions.
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Yeung, Albert T., and Subbaraju Datla. "Fundamental formulation of electrokinetic extraction of contaminants from soil." Canadian Geotechnical Journal 32, no. 4 (August 1, 1995): 569–83. http://dx.doi.org/10.1139/t95-060.
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Electro-osmosis and ionic migration are the basic cleanup mechanisms in the electrokinetic extraction of contaminants from fine-grained soils. These are coupled flows as the flows of fluid and contaminants are driven by an externally applied electrical gradient. Moreover, other electrochemical reactions will occur simultaneously during the process. The most pronounced effect is the generation of pH gradient in the soil. The change of pH in the pore fluid can have a significant impact on the degree of sorption and desorption of chemicals on soil particle surfaces, complexes formation and precipitation of chemical species, and dissociation of organic acids; thus affecting the feasibility and efficiency of the cleanup technique tremendously. An attempt is made to formulate the coupled flows of ionic contaminants and the resulting change of pH in the pore fluid during the electrokinetic extraction process. The coupled flows of contaminants are formulated by the formalism of nonequilibrium thermodynamics. The pH is determined as a function of time and space by maintaining electrical neutrality throughout the system all the times. A numerical model NEUTRAL is developed to simulate the processes. The good agreement between computed and experimental results published in the literature indicates that the approach is a valid step toward a better understanding of the physics and chemistry involved during electrokinetic treatment of contaminated soils. Key words : electrokinetics, in situ remediation, contaminated soil, coupled flows, electrochemistry, nonequilibrium thermodynamics.
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Hou, Peng, Yang Ju, Chengzheng Cai, Lin Gao, and Shanjie Su. "Lattice Boltzmann simulation of fluid flow induced by thermal effect in heterogeneity porous media." Thermal Science 21, suppl. 1 (2017): 193–200. http://dx.doi.org/10.2298/tsci17s1193h.
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In this paper, a coupled lattice Boltzmann model is used to visually study fluid flow induced by thermal effect in heterogeneity porous media reconstructed by the quartet structure generation set. The fluid flow behavior inside porous media is presented and analyzed under different conditions. The simulation results indicate that the pore morphological properties of porous media and the Rayleigh number have noticeable impact on the velocity distribution and flow rate of fluid.
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Shen, Yiyao, Zilan Zhong, Liyun Li, and Xiuli Du. "Nonlinear Solid–Fluid Coupled Seismic Response Analysis of Layered Liquefiable Deposit." Applied Sciences 12, no. 11 (June 1, 2022): 5628. http://dx.doi.org/10.3390/app12115628.
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A seismic response analysis of layered, liquefiable sites plays an important role in the seismic design of both aboveground and underground structures. This study presents a detailed dynamic site response analysis procedure with advanced nonlinear soil constitutive models for non-liquefiable and liquefiable soils in the OpenSees computational platform. The stress ratio controlled, bounding surface plasticity constitutive model, PM4Sand, is used to simulate the nonlinear response of the liquefiable soil layers subjected to two seismic ground motions with different characteristics. The nonlinear hysteretic behavior of the non-liquefiable soil under earthquake excitations is captured by the Pressure Independent Multi Yield kinematic plasticity model with a von Mises multi-yield surface. The soil elements are modelled utilizing the solid–fluid fully coupled plane-strain u-p elements. The seismic response of the layered liquefiable site in terms of the development of excess pore water pressure, acceleration, ground surface settlement, and stress–strain and effective stress path time histories under two representative earthquake excitations are investigated in this study. The numerical results indicate that both the characteristics of ground motions and the site profile have a significant influence on the dynamic response of the layered liquefiable site. Under the same intensity of ground motion, the loose sand layer with a 35% relative density is more prone to liquefaction and contractive deformation, which causes irreversible residual deformation and vertical settlement. The saturated soil layer can effectively filter the high-frequency components and amplify the low-frequency components of ground motions. Moreover, the liquified site produces a 40% post-earthquake consolidation settlement after the excess pore pressure dissipation.
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Zhao, Mo Li, and Qiang Yong Zhang. "Application of State Equation Method for Coupled Hydro-Mechanical Analysis in Dual-Porosity Media." Advanced Materials Research 575 (October 2012): 59–63. http://dx.doi.org/10.4028/www.scientific.net/amr.575.59.
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Seepage is one of the major influence factors for engineering stability. In this study, the equations of hydro-mechanical coupling in dual-porosity media including the governing equations of deformation and seepage are employed. The fluid gravity in whole system is considered in the seepage governing equation. The solid displacement, pore fluid pressure and fissure fluid pressure are the unknown qualities. The finite element formulation of the governing equations are acquired after using the Galerkin discretization technique. The physical parameters are discussed here. Finally, the state equation method is applied to solve the finite element equations.
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Kim, J., H. A. A. Tchelepi, and R. Juanes. "Rigorous Coupling of Geomechanics and Multiphase Flow with Strong Capillarity." SPE Journal 18, no. 06 (November 12, 2013): 1123–39. http://dx.doi.org/10.2118/141268-pa.
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Summary We study sequential formulations for coupled multiphase flow and reservoir geomechanics. First, we identify the proper definition of effective stress in multiphase-fluid systems. Although the average pore-pressure p¯ —defined as the sum of the product of saturation and pressure of all the fluid phases that occupy the pore space—is commonly used to describe multiphase-fluid flow in deformable porous media, it can be shown that the "equivalent" pore pressure pE —defined as p¯ minus the interfacial energy—is the appropriate quantity (Coussy 2004). We show, by means of a fully implicit analysis of the system, that only the equivalent pore pressure pE leads to a continuum problem that is thermodynamically stable (thus, numerical discretizations on the basis of the average pore pressure p¯ cannot render unconditionally stable and convergent schemes). We then study the convergence and stability properties of sequential-implicit coupling strategies. We show that the stability and convergence properties of sequential-implicit coupling strategies for single-phase flow carry over for multiphase systems if the equivalent pore pressure pE is used. Specifically, the undrained and fixed-stress schemes are unconditionally stable, and the fixed-stress split is superior to the undrained approach in terms of convergence rate. The findings from stability theory are verified by use of nonlinear simulations of two-phase flow in deformable reservoirs.
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Zhao, Yinuo, and Zhehui Jin. "Hydrocarbon-Phase Behaviors in Shale Nanopore/Fracture Model: Multiscale, Multicomponent, and Multiphase." SPE Journal 24, no. 06 (October 14, 2019): 2526–40. http://dx.doi.org/10.2118/198908-pa.
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Summary Hydrocarbon recovery from shale subformations has greatly contributed to the global energy supply and has been constantly reshaping the energy sector. Oil production from shale is a complex process in which multicomponent–fluid mixtures experience multiphase transitions in multiscale volumes (i.e., nanoscale pores are connected to fractures/macropores). Understanding such complicated phenomena plays a critical role in the estimation of ultimate oil recovery, well productivity, and reserves estimation, and ultimately in policy making. In this work, we use density–functional theory (DFT) to explicitly consider fluid/surface interactions, inhomogeneous–density distributions in nanopores, volume partitioning in nanopores, and connected macropores/natural fractures to study the complex multiphase transitions of multicomponent fluids in multiscale volumes. We found that vapor–like and liquid–like phases can coexist in nanopores when pressure is between the bubblepoint and dewpoint pressures of nanoconfined fluids, both of which are much lower than those of the originally injected hydrocarbon mixtures. As the volume ratio of the bulk at the initial condition to pores decreases, both the bubblepoint and the dewpoint in nanopores increase and the pore two–phase region expands. Within the pore two–phase region, both C1 and C3 are released from the nanopores to the bulk phase as pressure declines. Meanwhile, both liquid and vapor phases become denser as pressure drops. By further decreasing pressure below the dewpoint of confined fluids, C3 in the nanopore can be recovered. Throughout the process, the bulk–phase composition varies, which is in line with the field observation. Collectively, this work captures the coupled complexity of multicomponent and multiphase fluids in multiscale geometries that is inherent to shale reservoirs and provides a theoretical foundation for reservoir simulation, which is significant for the accurate prediction of well productivity and ultimate oil recovery in shale reservoirs.
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Szűcs, Herman. "Reconstruction of 3D Porous Geometry for Coupled FEM-CFD Simulation." Periodica Polytechnica Mechanical Engineering 66, no. 2 (March 22, 2022): 129–36. http://dx.doi.org/10.3311/ppme.19438.
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Porous materials can be found in numerous areas of life (e. g., applied science, material science), however, the simulation of the fluid flow and transport phenomena through porous media is a significant challenge nowadays. Numerical simulations can help to analyze and understand physical processes and different phenomena in the porous structure, as well as to determine certain parameters that are difficult or impossible to measure directly or can only be determined by expensive and time-consuming experiments. The basic condition for the numerical simulations is the 3D geometric model of the porous material sample, which is the input parameter of the simulation. For this reason, geometry reconstruction is highly critical for pore-scale analysis. This paper introduces a complex process for the preparation of the microstructure's geometry in connection with a coupled FEM-CFD two-way fluid-structure interaction simulation. Micro-CT has been successfully applied to reconstruct both the fluid and solid phases of the used porous material.
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Hada, Kodai, Mohammadreza Shirzadi, Tomonori Fukasawa, Kunihiro Fukui, and Toru Ishigami. "Numerical simulation of aerosol permeation through microstructure of face masks coordinating with x-ray computed tomography images." AIP Advances 12, no. 12 (December 1, 2022): 125119. http://dx.doi.org/10.1063/5.0129087.
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Face masks act as air filters that collect droplets and aerosols, and they are widely used to prevent infectious diseases, such as COVID-19. Herein, we present a numerical simulation model to understand the collection behavior of aerosols containing submicron-sized droplets inside a realistic microstructure of commercially available face masks. Three-dimensional image analysis by x-ray computed tomography is used to obtain the microstructures of two types of commercial face masks, and the aerosol permeation behavior in the obtained microstructures is investigated with a numerical method coupled with computational fluid dynamics and a discrete phase model. To describe the complex geometry of the actual fibers, a wall boundary model is used, in which the immersed boundary method is used for the fluid phase, and the signed distance function is used to determine the contact between the droplet and fiber surface. Six different face-mask domains are prepared, and the pressure drop and droplet collection efficiency are calculated for two different droplet diameters. The face-mask microstructure with the relatively larger pore, penetrating the main flow direction, shows a high quality factor. A few droplets approach the pore accompanied by fluid flow and fibers collect them near the pore. To verify the effect of the pore on the collection behavior, six different model face-mask domains of variable pore sizes were created. Additionally, droplet collection near the pore is observed in the model face-mask domains. Specific pore-sized model masks performed better than those without, suggesting that the large pore may enhance performance.
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Bart, M., J. F. Shao, D. Lydzba, and M. Haji-Sotoudeh. "Coupled hydromechanical modeling of rock fractures under normal stress." Canadian Geotechnical Journal 41, no. 4 (August 1, 2004): 686–97. http://dx.doi.org/10.1139/t04-018.
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In this paper, a nonlinear poromechanical model is developed for a single rock fracture under normal stress. The fracture is represented by a set of voids, and the progressive fracture displacement is considered as a modification process of void space. Based on experimental data obtained from three representative rock fractures, the constitutive model is formulated through an extension of Biot poroelasticity theory to a saturated fracture. A generalized poroelastic coupling coefficient is introduced to describe the interaction between pore fluid pressure and fracture deformation. This coefficient is expressed as a function of fracture aperture. Five parameters involved in the model have been determined from mechanical and poromechanical compression tests. The validity of the model is checked on fluid flow tests under different normal stresses. Comparisons between numerical simulations and experimental data are provided.Key words: hydromechanical coupling, interfaces, joints, poroelasticity, rock mechanics, fractures.
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Li, Kun, Xingyao Yin, Zhaoyun Zong, and Dario Grana. "Estimation of porosity, fluid bulk modulus, and stiff-pore volume fraction using a multitrace Bayesian amplitude-variation-with-offset petrophysics inversion in multiporosity reservoirs." GEOPHYSICS 87, no. 1 (November 18, 2021): M25—M41. http://dx.doi.org/10.1190/geo2021-0029.1.
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The estimation of petrophysical and fluid-filling properties of subsurface reservoirs from seismic data is a crucial component of reservoir characterization. Seismic amplitude-variation-with-offset (AVO) inversion driven by rock physics is an effective approach to characterize reservoir properties. In general, PP-wave reflection coefficients, elastic moduli, and petrophysical parameters are nonlinearly coupled, especially in multiple-type pore-space reservoirs, which makes seismic AVO petrophysics inversion ill-posed. We have developed a new approach that combines Biot-Gassmann’s poroelasticity theory with Russell’s linear AVO approximation, to estimate the reservoir properties including elastic moduli and petrophysical parameters based on multitrace probabilistic AVO inversion algorithm. We first derive a novel PP-wave reflection coefficient formulation in terms of porosity, stiff-pore volume fraction, rock-matrix shear modulus, and fluid bulk modulus to incorporate the effect of pore structures on elastic moduli by considering the soft and stiff pores with different aspect ratios in sandstone reservoirs. Through the analysis of the four types of PP-wave reflection coefficients, the approximation accuracy and inversion feasibility of the derived formulation are verified. Our stochastic inversion method aims to predict the posterior probability density function in a Bayesian setting according to a prior Laplace distribution with vertical correlation and prior Gaussian distribution with lateral correlation of model parameters. A Metropolis-Hastings stochastic sampling algorithm with multiple Markov chains is developed to simulate the posterior models of porosity, stiff-pore volume fraction, rock-matrix shear modulus, and fluid bulk modulus from seismic AVO gathers. The applicability and validity of our inversion method is illustrated with synthetic examples and a real data application.
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El Safti, Hisham, Matthias Kudella, and Hocine Oumeraci. "MODELLING WAVE-INDUCED RESIDUAL PORE PRESSURE AND DEFORMATION OF SAND FOUNDATIONS UNDERNEATH CAISSON BREAKWATERS." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 56. http://dx.doi.org/10.9753/icce.v33.structures.56.
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A finite volume model is developed for modelling the behaviour of the seabed underneath monolithic breakwaters. The fully coupled and fully dynamic Biot’s governing equations are solved in a segregated approach. Two simplifications to the governing equations are presented and tested: (i) the pore fluid acceleration is completely neglected (the u-p approximation) and (ii) only the convective part is neglected. It is found that neglecting the pore fluid convection does not reduce the computational time for the presented model. Verification of the model results with the analytical solution of the quasi-static equations is presented. A multi-yield surface plasticity model is implemented in the model to simulate the foundation behaviour under cyclic loads. Preliminary validation of the model with large-scale physical model data is presented.
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Toumelin, Emmanuel, Carlos Torres-Verdin, Boqin Sun, and Keh-Jim Dunn. "Limits of 2D NMR Interpretation Techniques to Quantify Pore Size, Wettability, and Fluid Type: A Numerical Sensitivity Study." SPE Journal 11, no. 03 (September 1, 2006): 354–63. http://dx.doi.org/10.2118/90539-pa.
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Summary Two-dimensional (2D) NMR techniques have been proposed as efficient methods to infer a variety of petrophysical parameters, including mixed fluid saturation, in-situ oil viscosity, wettability, and pore structure. However, no study has been presented to quantify the petrophysical limitations of such methods. We address this problem by introducing a pore-scale framework to accurately simulate suites of NMR measurements acquired in complex rock/fluid models. The general pore-scale framework considered in this paper is based on NMR random walks for multiphase fluid diffusion and relaxations, combined with Kovscek's pore-scale model for two-phase fluid saturation and wettability alteration. We use standard 2D NMR methods to interpret synthetic data sets for diverse petrophysical configurations, including two-phase saturations with different oil grades, mixed wettability, or carbonate pore heterogeneity. Results from our study indicate that for both water-wet and mixed-wet rocks, T2 (transverse relaxation)/D (diffusion) maps are reliable for fluid typing without the need for independently determined cutoffs. However, significant uncertainty exists in the estimation of fluid type, wettability, and pore structure with 2D NMR methods in cases of mixed-wettability states. Only light oil wettability can be reliably detected with 2D NMR interpretation methods. Diffusion coupling in carbonate rocks introduces additional problems that cannot be circumvented with current 2D NMR techniques. Introduction Wettability state and oil viscosity can play a significant role in the NMR response of saturated rocks. This property of NMR measurements has been discussed in recent papers (Freedman et al. 2003) for particular examples of rock systems. However, to date, no systematic study has been published of the reliability and accuracy of NMR methods to assess fluid viscosity and wettability, including cases of mixed wettability. This paper quantifies the sensitivity of 2D relaxation/diffusion NMR techniques to mixed wettability and fluid viscosity in generic rock models. Given that measurements are often made on rock samples with uncertain petrophysical properties and therefore uncertain corresponding measurement contributions, the work described in this paper is based on the numerical simulation of pore-scale systems. We introduce a general numerical model that simultaneously includes immiscible fluid viscosities, water or mixed wettability, variable fluid saturations and history, and disordered complexity of rock structure. Geometrical fluid distributions at the pore scale were considered a function of pore size, saturation history, and wettability following Kovscek et al.'s model of mixed-oil-wet rocks (1993). We simulated suites of NMR measurements with random walkers within these pore-scale geometries, and subsequently inverted into relaxation/diffusion NMR maps. The objective of this paper is to assess the accuracy of 2D NMR interpretation techniques to detect fluid and wettability types, and to quantify pore-size distributions. The first section of the paper summarizes the principles and limitations of current NMR petrophysical interpretation. We then summarize our pore-scale modeling procedure, its assumptions, and limitations. Subsequent sections analyze simulation results obtained for drainage and imbibition involving water-wettability and mixed-oil-wettability with partial saturations of water and different hydrocarbon types in a generic clay-free rock model. Next, we consider the case of coupled carbonate rocks with emphasis on the assessment of wettability and microporosity.
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Yang, Jianwen. "Finite element modeling of transient saline hydrothermal fluids in multifaulted sedimentary basins: implications for ore-forming processes." Canadian Journal of Earth Sciences 43, no. 9 (September 1, 2006): 1331–40. http://dx.doi.org/10.1139/e06-021.
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A finite element algorithm is presented to simulate fully coupled transient fluid flow, heat, and solute transport in discretely fractured porous media, and yield the regional-scale free thermohaline convection patterns for the McArthur Basin in northern Australia. Numerical results indicate that salinity variation throughout the basin has an important influence on fluid migration and the thermal regime. The spatial and temporal distribution of saline fluids can either promote or impede free convection. Relatively saline conditions (10 wt.%) at the basin floor favour free convection; whereas, high salinities at depth suppress the development of convective hydrothermal systems. When salinity increases with depth, a higher geothermal gradient is required to induce and maintain significant fluid circulation. The implication is that sedimentary-exhalative ore deposits are more easily formed when evaporation first produces surface brines, and then these brines sink and displace pore waters in the basin.
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Alihussein, Hussein, Martin Geier, and Manfred Krafczyk. "A Parallel Coupled Lattice Boltzmann-Volume of Fluid Framework for Modeling Porous Media Evolution." Materials 14, no. 10 (May 12, 2021): 2510. http://dx.doi.org/10.3390/ma14102510.
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In this paper, we present a framework for the modeling and simulation of a subset of physical/chemical processes occurring on different spatial and temporal scales in porous materials. In order to improve our understanding of such processes on multiple spatio-temporal scales, small-scale simulations of transport and reaction are of vital importance. Due to the geometric complexity of the pore space and the need to consider a representative elementary volume, such simulations require substantial numerical resolutions, leading to potentially huge computation times. An efficient parallelization of such numerical methods is thus vital to obtain results in acceptable wall-clock time. The goal of this paper was to improve available approaches based on lattice Boltzmann methods (LBMs) to reliably and accurately predict the combined effects of mass transport and reaction in porous media. To this end, we relied on the factorized central moment LBM as a second-order accurate approach for modeling transport. In order to include morphological changes due to the dissolution of the solid phase, the volume of fluid method with the piece-wise linear interface construction algorithm was employed. These developments are being integrated into the LBM research code VirtualFluids. After the validation of the analytic test cases, we present an application of diffusion-controlled dissolution for a pore space obtained from computer tomography (CT) scans.
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Dvorkin, Jack, and Amos Nur. "Dynamic poroelasticity: A unified model with the squirt and the Biot mechanisms." GEOPHYSICS 58, no. 4 (April 1993): 524–33. http://dx.doi.org/10.1190/1.1443435.
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The velocities and attenuation of seismic and acoustic waves in rocks with fluids are affected by the two most important modes of fluid/solid interaction: (1) the Biot mechanism where the fluid is forced to participate in the solid’s motion by viscous friction and inertial coupling, and (2) the squirt‐flow mechanism where the fluid is squeezed out of thin pores deformed by a passing wave. Traditionally, both modes have been modeled separately, with the Biot mechanism treated in a macroscopic framework, and the squirt flow examined at the individual pore level. We offer a model which treats both mechanisms as coupled processes and relates P‐velocity and attenuation to macroscopic parameters: the Biot poroelastic constants, porosity, permeability, fluid compressibility and viscosity, and a newly introduced microscale parameter—a characteristic squirt‐flow length. The latter is referred to as a fundamental rock property that can be determined experimentally. We show that the squirt‐flow mechanism dominates the Biot mechanism and is responsible for measured large velocity dispersion and attenuation values. The model directly relates P‐velocity and attenuation to measurable rock and fluid properties. Therefore, it allows one to realistically interpret velocity dispersion and/or attenuation in terms of fluid properties changes [e.g., viscosity during thermal enhanced oil recovery (EOR)], or to link seismic measurements to reservoir properties. As an example of the latter transformation, we relate permeability to attenuation and achieve good qualitative correlation with experimental data.