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1.
We consider flow and upscaling of flow properties from pore scale to Darcy scale, when the pore-scale geometry is changing. The idea is to avoid having to solve for the pore evolution at the pore scale, because this results in unmanageable complexity. We propose to use stochastic modeling to parametrize plausible modifications of the pore geometry and to construct distributions of permeability parametrized by Darcy-scale variables. To localize the effects of, e.g., clogging, we introduce an intermediate scale of pore-network models. We use local Stokes solvers to calibrate the throat permeability. 相似文献
2.
软土地基电渗固结理论分析与数值模拟 总被引：3，自引：0，他引：3
电渗固结是加速软土固结、提高地基承载力的有效技术。传统的电渗固结理论假设土体的物理力学、水力学和电学特性均匀稳定,其理论解答与试验结果差别较大。针对电渗固结处理过程,对土体位移场、渗流场和电场的耦合特征进行了理论分析,根据电荷守恒原理、水流连续原理和Biot固结理论,建立了电渗固结过程的多场耦合控制方程;考虑土体相关特性参数的非线性关系,开发了有限元软件用于分析电渗过程中电场强度、土体位移以及超静孔隙水压力的变化特征。计算结果与理论数据吻合较好,能够反映土体相关特性参数非线性关系对结果的影响。软件能够为电渗固结系统设计提供参考依据。 相似文献
3.
软土在低水力坡降下的渗流会偏离达西定律,即为非达西渗流模式。假设孔隙水渗透服从指数渗流模式,采用镜像法原理推导了浅埋单孔和双孔圆形隧道非达西渗流场的解析解。结合算例,对浅埋圆形隧道非达西渗流解析解与达西渗流解析解进行了对比分析与验证,并对非达西渗流指数、隧道周围土体与衬砌渗流系数比值对隧道渗流场的影响进行了讨论。结果表明：非达西渗流指数、渗流系数比值对隧道渗流量和周围土体孔压均有较大的影响;随着渗流指数逐渐增大,土体内水头损失加快,隧道周围土体孔压及渗流量逐渐减小;随着土体与衬砌渗流系数比值逐渐增大,衬砌排水能力增强,隧道渗流量逐渐增大,隧道周围土体孔压减小更大。 相似文献
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Experiment equipments involved in the single tube fracture and double tube fracture models are designed to research the characteristics of groundwater flow and solute transport in filled fracture. During the experiment, the state of groundwater flow can be characterized as linear flow, and satisfies Darcy’s law. Therefore, based on the pipe flow of hydraulics and Darcy’s law, the flow rate and water flow velocity can be calculated. Also, dispersion parameters were calculated with the fitting of observed data and analytical solution in the single tube fracture model. Furthermore, effects of some factors on solute transport are involved in the double tube fracture model, and length of branch fracture, particles’ diameter and flow rate in water inlet have been discussed. Results show that the arrival time of concentration peak value in the single tube fracture model is faster than that in the double tube fracture model, and two concentration peak values exist in the double tube fracture model. Arrival time of concentration peak value is faster with the increase of branch fracture length. Furthermore, if the branch fracture is longer, arrival time of the first concentration peak value is faster, while arrival time of the second concentration peak value is slower, relative to short branch fracture. 相似文献
6.
The coupled heat-fluid-stress problem of circular wellbore or spherical cavity subjected to a constant temperature change and a constant fluid flow rate is considered. Transient analytical solutions for temperature, pore pressure and stress are developed by coupling conductive heat transfer with Darcy fluid flow in a poroelastic medium. They are applicable to low permeability porous media suitable for liquid-waste disposal and also simulating reservoir for enhanced oil recovery, where conduction dominates the heat transfer process. A full range of solutions is presented showing separately the effects of temperature and fluid flow on pore pressure and stress development. It is shown that injection of warm fluid can be used to restrict fracture development around wellbores and cavities and generally to optimize a fluid injection operation. Both the limitations of the solutions and the convective flow effect are addressed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
7.
Analytical solutions for advective–dispersive solute transport in double‐layered finite porous media
Peter John Cleall 《国际地质力学数值与分析法杂志》2011,35(4):438-460
Analytical solutions for advection and dispersion of a conservative solute in a one‐dimensional double‐layered finite porous media are presented. The solutions are applicable to five scenarios that have various combinations of fixed concentration, fixed flux and zero concentration gradient conditions at the inlet and outlet boundaries that provide a wide number of options. Arbitrary initial solute concentration distributions throughout the media can be considered via explicit formulations or numerical integration. The analytical solutions presented have been verified against numerical solutions from a finite‐element‐based approach and an existing closed‐form solution for double‐layered media with an excellent correlation being found in both cases. A practical application pertaining to advective transport induced by consolidation of underlying sediment layers on contaminant movement within a capped contaminated sediment system is presented. Comparison of the calculated concentrations and fluxes with alternative approaches clearly illustrates the need to consider advection processes. Consideration of the different features of contaminant transport due to varying pore‐water velocity fields in primary consolidation and secondary consolidation stages is achieved via the use of non‐uniform initial concentration distributions within the proposed analytical solutions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
页岩气是一种潜在资源量巨大的非常规天然气资源,页岩气藏具有多尺度的孔渗结构及多种渗流形态,研究页岩气藏储渗特征能够为页岩气的勘探开发提供理论支撑。该研究选取了柴达木盆地东部石炭系克鲁克组与怀头他拉组的页岩钻井岩心共5个样品,应用氩离子抛光扫描电镜实验与孔径分布测试(包括压汞法、氮气吸附法、二氧化碳吸附法)对页岩的孔隙结构特征进行定性定量测试。基于页岩气质量流量渗流模型,给出页岩表观渗透率与平均压力的关系。通过甲烷渗流模拟实验测定页岩的表观渗透率。从表观渗透率随平均压力的变化特征出发,分析页岩储层中的气体渗流规律。研究结果表明：页岩气的渗流形态包括滑脱流、扩散流及达西流。在低压情况下,渗透率低的页岩中以扩散流为主,其次为滑脱流。随渗透率的增大,渗流主要形式转变为滑脱流。当压力大于2 MPa时渗流形态以达西流为主,滑脱与扩散行为不明显。研究区内页岩微孔与中孔发育较多,达西渗透率与大孔的孔隙体积相关性较大,扩散流对表观渗透率的贡献与50 nm以下的孔隙孔体积比例有一定的相关性。低压下扩散流对表观渗透率的贡献较大,扩散流是一种非常重要的页岩气运移形式。 相似文献
9.
Conventional modelling of transport problems for porous media usually assumes that the Darcy flow velocities are steady. In certain practical situations, the flow velocity can exhibit time‐dependency, either due to the transient character of the flow process or time dependency in the boundary conditions associated with potential flow. In this paper, we consider certain one‐ and three‐dimensional problems of the advective transport of a chemical species in a fluid‐saturated porous region. In particular, the advective flow velocity is governed by the piezo‐conduction equation that takes into account the compressibilities of the pore fluid and the porous skeleton. Time‐ and/or mesh‐refining adaptive schemes used in the computational modelling are developed on the basis of a Fourier analysis, which can lead to accurate and optimal solutions for the advective transport problem with time‐ and space‐dependent advective flow velocity distributions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
10.
M. Oostrom Y. Mehmani P. Romero-Gomez Y. Tang H. Liu H. Yoon Q. Kang V. Joekar-Niasar M. T. Balhoff T. Dewers G. D. Tartakovsky E. A. Leist N. J. Hess W. A. Perkins C. L. Rakowski M. C. Richmond J. A. Serkowski C. J. Werth A. J. Valocchi T. W. Wietsma C. Zhang 《Computational Geosciences》2016,20(4):857-879
11.
We consider a system of nonlinear partial differential equations that arises in the modeling of two-phase flows in a porous medium. The phase velocities are modeled using a Brinkman regularization of the classical Darcy’s law. We propose a notion of weak solution for these equations and prove existence of these solutions. An efficient finite difference scheme is proposed and is shown to converge to the weak solutions of this system. The Darcy limit of the Brinkman regularization is studied numerically using the convergent finite difference scheme in two space dimensions as well as using both analytical and numerical tools in one space dimension. The results suggest that the Brinkman regularization may not approximate the accepted entropy solutions of the Darcy model and raise fundamental questions about the use of Brinkman type models in two-phase flows. 相似文献
12.
The possibility that gradients in concentration may develop within single pores and fractures, potentially giving rise to scale-dependent mineral dissolution rates, was investigated with experimentally validated reactive transport modeling. Three important subsurface mineral phases that dissolve at widely different rates, calcite, plagioclase, and iron hydroxide, were considered. Two models for analyzing mineral dissolution kinetics within a single pore were developed: (1) a Poiseuille Flow model that applies laboratory-measured dissolution kinetics at the pore or fracture wall and couples this to a rigorous treatment of both advective and diffusive transport within the pore, and (2) a Well-Mixed Reactor model that assumes complete mixing within the pore, while maintaining the same reactive surface area, average flow rate, geometry, and multicomponent chemistry as the Poiseuille Flow model. For the case of a single fracture, a 1D Plug Flow Reactor model was also considered to quantify the effects of longitudinal versus transverse mixing. Excellent agreement was obtained between results from the Poiseuille Flow model and microfluidic laboratory experiments in which pH 4 and 5 solutions were flowed through a single 500 μm diameter by 4000 μm long cylindrical pore in calcite. The numerical modeling and time scale analysis indicated that rate discrepancies arise primarily where concentration gradients develop under two necessary conditions: (1) comparable rates of reaction and advective transport, and (2) incomplete mixing via molecular diffusion. For plagioclase and iron hydroxide, the scaling effects are negligible at the single pore and fracture scale because of their slow rates. In the case of calcite, where dissolution rates are rapid, scaling effects can develop at high flow rates from 0.1 to 1000 cm/s and for fracture lengths less than 1 cm. Under more normal flow conditions where flow is usually slower than 0.001 cm/s, however, mixing via molecular diffusion is effective in homogenizing the concentration field, thus eliminating any discrepancies between the Poiseuille Flow and the Well-Mixed Reactor model. The analysis suggests that concentration gradients are unlikely to develop within single pores and fractures under typical geological/hydrologic conditions, implying that the discrepancy between laboratory and field rates must be attributed to other factors. 相似文献
13.
A. P. S. Selvadurai 《国际地质力学数值与分析法杂志》2004,28(2):191-208
This paper examines the problem of the advective transport of a contaminant from sources in the shape of either a penny-shaped crack or an elongated needle-shaped cavity located in a porous medium of infinite extent. The advective transport is induced by Darcy flow in the porous medium, where the internal boundary is maintained at a constant potential. The paper presents an approximate analytical solution to this problem, which is deduced from a formulation that models a cavity in the shape of either an oblate or a prolate spheroid. The results also represent one of the few spatially three-dimensional exact analytical solutions for the, albeit linear, hyperbolic problem governing the contaminant transport problem. The paper also presents a canonical proof of uniqueness for advective contaminant transport problems associated with media of infinite extent. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
14.
Chongbin Zhao B. E. Hobbs P. Hornby A. Ord Shenglin Peng Liangming Liu 《国际地质力学数值与分析法杂志》2008,32(9):1107-1130
The chemical‐dissolution front propagation problem exists ubiquitously in many scientific and engineering fields. To solve this problem, it is necessary to deal with a coupled system between porosity, pore‐fluid pressure and reactive chemical‐species transport in fluid‐saturated porous media. Because there was confusion between the average linear velocity and the Darcy velocity in the previous study, the governing equations and related solutions of the problem are re‐derived to correct this confusion in this paper. Owing to the morphological instability of a chemical‐dissolution front, a numerical procedure, which is a combination of the finite element and finite difference methods, is also proposed to solve this problem. In order to verify the proposed numerical procedure, a set of analytical solutions has been derived for a benchmark problem under a special condition where the ratio of the equilibrium concentration to the solid molar density of the concerned chemical species is very small. Not only can the derived analytical solutions be used to verify any numerical method before it is used to solve this kind of chemical‐dissolution front propagation problem but they can also be used to understand the fundamental mechanisms behind the morphological instability of a chemical‐dissolution front during its propagation within fluid‐saturated porous media. The related numerical examples have demonstrated the usefulness and applicability of the proposed numerical procedure for dealing with the chemical‐dissolution front instability problem within a fluid‐saturated porous medium. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
15.
Retention of surface-modified nanoscale zero-valent iron (NZVI) particles in the porous media near the point of injection has been reported in the recent studies. Retention of excess particles in porous media can alter the media properties. The main objectives of this study are, therefore, to evaluate the effect of particle retention on the porous media properties and its implication on further NZVI particle transport under different flow conditions. To achieve the objectives, a one-dimensional transport model is developed by considering particle deposition, detachment, and straining mechanisms along with the effect of changes in porosity resulting from retention of NZVI particles. Two different flow conditions are considered for simulations. The first is a constant Darcy’s flow rate condition, which assumes a change in porosity, causes a change in pore water velocity and the second, is a constant head condition, which assumes the change in porosity, influence the permeability and hydraulic conductivity (thus Darcy’s flow rate). Overall a rapid decrease in porosity was observed as a result of high particle retention near the injection points resulting in a spatial distribution of deposition rate coefficient. In the case of constant head condition, the spatial distribution of Darcy’s velocities is predicted due to variation in porosity and hydraulic conductivity. The simulation results are compared with the data reported from the field studies; which suggests straining is likely to happen in the real field condition. 相似文献
16.
深层地热能是一种清洁环保的可再生能源,尾水回灌是深层地热可持续开发利用的重要保证,但目前国内地热尾水回灌还处在起步阶段,地热尾水回灌方案优化设计的理论模型尚不成熟。文章结合示踪试验,提出了基于等效渗流通道模型的热储参数反演与开采井热突破预测的完整理论框架。应用多孔介质溶质运移理论,修正了等效渗流通道中的溶质浓度解析解,并联合移动渐近线法提出了热储参数反演理论模型;推导了等效渗流通道中的对流传热解析模型,可对开采井中的水温变化进行预测。依托山东省德州市平原县魏庄社区地热对井示踪试验,应用该理论框架进行了示踪试验反演及开采井热突破预测,并对影响开采井热突破的主要因素进行了敏感性分析。 相似文献
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The state of the art of modeling fluid flow in shale reservoirs is dominated by dual-porosity models which divide the reservoirs into matrix blocks that significantly contribute to fluid storage and fracture networks which principally control flow capacity. However, recent extensive microscopic studies reveal that there exist massive micro- and nano-pore systems in shale matrices. Because of this, the actual flow mechanisms in shale reservoirs are considerably more complex than can be simulated by the conventional dual-porosity models and Darcy’s law. Therefore, a model capturing multiple pore scales and flow can provide a better understanding of the complex flow mechanisms occurring in these reservoirs. This paper presents a micro-scale multiple-porosity model for fluid flow in shale reservoirs by capturing the dynamics occurring in three porosity systems: inorganic matter, organic matter (mainly kerogen), and natural fractures. Inorganic and organic portions of shale matrix are treated as sub-blocks with different attributes, such as wettability and pore structures. In kerogen, gas desorption and diffusion are the dominant physics. Since the flow regimes are sensitive to pore size, the effects of nano-pores and micro-pores in kerogen are incorporated into the simulator. The multiple-porosity model is built upon a unique tool for simulating general multiple-porosity systems in which several porosity systems may be tied to each other through arbitrary connectivities. This new model allows us to better understand complex flow mechanisms and eventually is extended into the reservoir scale through upscaling techniques. Sensitivity studies on the contributions of the different flow mechanisms and kerogen properties give some insight as to their importance. Results also include a comparison of the conventional dual-porosity treatment and show that significant differences in fluid distributions and dynamics are obtained with the improved multiple-porosity simulation. 相似文献
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To be able to predict contaminant transport in groundwater, an accurate conceptual and physical understanding of aquifer properties
at multiple scales is required. In this study, physical and hydraulic properties of a coastal sand aquifer were derived using
micro and macro X-ray computed tomography (XCT) techniques. Qualitative and quantitative data improved conceptualisation of
the aquifer structure at micro and macro scale. At the macro scale (50-mm diameter by 1,500-mm long core) XCT images of undisturbed
drill core identified coarse grained laminae (not obvious to the naked eye) of increased porosity and permeability, variations
in mineral assemblage and particulate organic matter distribution within the core. Micro-XCT analysis (16-mm diameter cores)
of the three main aquifer layers provided quantitative micro-scale data on permeability, porosity, grain, pore and throat
size distribution statistics, and grain sphericity. Ratios of mean pore to grain diameter were ~0.65–0.75 and ratios of mean
throat to mean grain diameter were ~0.2. Multiple permeability and porosity values were derived from micro domains (~4.35 mm3) within each micro-XCT core. Permeability values varied between and within micro-XCT core samples reflecting the heterogeneity
at the millimetre core scale in these sediments. Sphericity values were similar for all three layers (average ~0.4) which
reflected SEM observations of the semi-spherical nature of the dominant quartz and feldspar grains. The results of this study
indicate that models based on the assumptions of homogeneity in depositional structure below centimetre scale may not suitably
address factors affecting flow and transport of contaminants. 相似文献
20.
运用岩石高压三轴加载装置和渗透压加载装置,对砂岩进行固定应力变渗透水压力试验,同时借助SOMATOMPLUS螺旋CT扫描机进行实时观测。通过试验结果分析,推出了基于CT数的岩石空隙率公式,从CT尺度上分析了岩石空隙率、渗透速度、渗流速度、微孔隙直径、渗透率等随渗透水压力的变化规律。结果表明:岩石的渗透参数随渗透压力的增加而增大,渗透参数随渗透压力的变化呈对数关系,这是由于渗透水压力使岩石内部空隙发生变形,这一变形为弹性变形;而渗流速度与渗透水压力呈线性关系,符合宏观尺度渗流的达西定律。 相似文献