共查询到20条相似文献，搜索用时 31 毫秒
1.
多孔介质中悬浮颗粒迁移和沉积特性的研究对地下污染物净化、石油开采、核废料处置、水土保持等有很重要的意义。对4种不同浓度的悬浮颗粒在3种不同的渗流速度下进行室内试验,研究悬浮颗粒的浓度对其迁移和沉积特性的影响。结果表明,在一定的悬浮颗粒浓度下,随着渗流速度的增加,穿透曲线中的悬浮颗粒的相对浓度也增大。同时,渗流速度一定时,悬浮颗粒的浓度存在一个临界值,小于该临界值,穿透曲线中的相对浓度随悬浮颗粒的浓度增大而增大;大于该临界值时,相对浓度随悬浮颗粒的浓度增大而减小。另外,悬浮颗粒的临界浓度是与渗流速度相关的,随着渗流速度增加,悬浮颗粒的临界浓度也逐渐增大 相似文献
2.
Rigoberto G. Sanabria Castro Sandra M. C. Malta Abimael F. D. Loula Luiz Landau 《Computational Geosciences》2001,5(4):301-330
A finite element formulation is proposed to approximate a nonlinear system of partial differential equations, composed by an elliptic subsystem for the pressure–velocity and a transport equation (convection–diffusion) for the concentration, which models the incompressible miscible displacement of one fluid by another in a rigid porous media. The pressure is approximated by the classical Galerkin method and the velocity is calculated by a post-processing technique. Then, the concentration is obtained by a Galerkin/least-squares space–time (GLS/ST) finite element method. A numerical analysis is developed for the concentration approximation. Then, stability, convergence and numerical results are presented confirming the a priori error estimates. 相似文献
3.
Rigoberto G. Sanabria Castro Sandra M. C. Malta Abimael F. D. Loula Luiz Landau 《Computational Geosciences》2002,5(4):301-330
A finite element formulation is proposed to approximate a nonlinear system of partial differential equations, composed by an elliptic subsystem for the pressure–velocity and a transport equation (convection–diffusion) for the concentration, which models the incompressible miscible displacement of one fluid by another in a rigid porous media. The pressure is approximated by the classical Galerkin method and the velocity is calculated by a post-processing technique. Then, the concentration is obtained by a Galerkin/least-squares space–time (GLS/ST) finite element method. A numerical analysis is developed for the concentration approximation. Then, stability, convergence and numerical results are presented confirming the a priori error estimates. 相似文献
4.
Some analytical solutions of one-dimensional advection–diffusion equation (ADE) with variable dispersion coefficient and velocity are obtained using Green’s function method (GFM). The variability attributes to the heterogeneity of hydro-geological media like river bed or aquifer in more general ways than that in the previous works. Dispersion coefficient is considered temporally dependent, while velocity is considered spatially and temporally dependent. The spatial dependence is considered to be linear and temporal dependence is considered to be of linear, exponential and asymptotic. The spatio-temporal dependence of velocity is considered in three ways. Results of previous works are also derived validating the results of the present work. To use GFM, a moving coordinate transformation is developed through which this ADE is reduced into a form, whose analytical solution is already known. Analytical solutions are obtained for the pollutant’s mass dispersion from an instantaneous point source as well as from a continuous point source in a heterogeneous medium. The effect of such dependence on the mass transport is explained through the illustrations of the analytical solutions. 相似文献
5.
Bilal Rashid Astor-Lonice Bal Glyn J. J. Williams Ann H. Muggeridge 《Computational Geosciences》2012,16(2):409-422
The vorticity of the displacement velocity is used to derive dimensionless numbers that can be used to quantify the relative
importance of viscosity ratio, gravity, diffusion/dispersion and permeability heterogeneity on secondary hydrocarbon recovery.
Using this approach, a new objective measure of the impact of permeability and porosity heterogeneity on reservoir performance
is obtained. This is used, in conjunction with other dimensionless numbers, to analyse the relative impact of heterogeneity,
buoyancy effects, mobility ratio and dispersion on breakthrough time and recovery at 1 pore volume injected during first contact
miscible gas injection. This is achieved using results obtained from detailed simulation of miscible displacements through
a range of geologically realistic reservoir models. This study goes some way towards developing a unified mathematical framework
to determine under which flow conditions reservoir heterogeneity becomes more important than other physical processes. We
propose that comparison of these dimensionless numbers can be used to identify the key factors controlling recovery and thus
assist the engineer in determining appropriate enhanced oil recovery techniques to improve recovery. 相似文献
6.
Analytical solutions of one-dimensional advection-diffusion equation with variable coefficients in a finite domain 总被引：1，自引：0，他引：1
Analytical solutions are obtained for one-dimensional advection-diffusion equation with variable coefficients in a longitudinal
finite initially solute free domain, for two dispersion problems. In the first one, temporally dependent solute dispersion
along uniform flow in homogeneous domain is studied. In the second problem the velocity is considered spatially dependent
due to the inhomogeneity of the domain and the dispersion is considered proportional to the square of the velocity. The velocity
is linearly interpolated to represent small increase in it along the finite domain. This analytical solution is compared with
the numerical solution in case the dispersion is proportional to the same linearly interpolated velocity. The input condition
is considered continuous of uniform and of increasing nature both. The analytical solutions are obtained by using Laplace
transformation technique. In that process new independent space and time variables have been introduced. The effects of the
dependency of dispersion with time and the inhomogeneity of the domain on the solute transport are studied separately with
the help of graphs. 相似文献
7.
半无限含水层中带衬砌隧洞渗流解析研究 总被引：3，自引：0，他引：3
现有关于半无限含水层中隧洞渗流的解析解不能考虑衬砌部分排水的特性。假定土体和衬砌均为饱和均匀连续介质,采用土体与衬砌分算;利用复变函数解决孔口问题基本方法,对土体采用共形映射坐标变换,将土体中的渗流方程转换为与衬砌部分类似的二维Laplace方程圆环域的Dirichlet问题;通过Fourier解法,根据边界条件并利用流量连续条件,求得半无限空间中带衬砌隧洞渗流量和衬砌周边水头解析解答。分析了径深比、土体与衬砌渗透系数相对值、内壁水压力等因素对渗流量和衬砌周边水头的影响,并与数值算例进行了比较。结果表明,对浅埋隧洞该解析解仍具有较好的精度,是简便、实用的计算方法。 相似文献
8.
CO_2-原油体系混相状态的渗流特性 总被引：1，自引：0，他引：1
为认识混相状态的CO2在油藏中的渗流特征,利用高温高压三维模拟装置对CO2-地层原油体系在油藏环境条件下的混相驱替过程进行研究.实验发现:模型产出液量与注入量存在较大差异;采收率、含水和气油比曲线亦表现出CO2在孔隙介质中渗流的复杂特征.由实时监测的含水饱和度分布场图分析认为:CO2与原油混相后,流体粘度降低、渗流阻力减小,这是提高采收率的重要原因之一;同时,CO2/原油相与部分接触水能形成近似于三相混相的状态.实验研究还表明CO2以高密度气体形式进入饱和水、饱和油无法进入的微孔隙,这是注入量和产出量不一致的主要原因. 相似文献
9.
We construct a new class of locally conservative numerical methods for two-phase immiscible flow in heterogeneous poroelastic media. Within the framework of the so-called iteratively coupled methods and fixed-stress split algorithm we develop mixed finite element methods for the flow and geomechanics subsystems which furnish locally conservative Darcy velocity and transient porosity input fields for the transport problem for the water saturation. Such hyperbolic equation is decomposed within an operator splitting technique based on a predictor–corrector scheme with the predictor step discretized by a higher-order non-oscillatory finite volume central scheme. The proposed scheme adopts an inhomogeneous dual mesh with variable cell size ruled by the local wave speed of propagation to compute numerical fluxes at cell edges. In the limit of small time steps the central scheme gives rise to a semidiscrete formulation for the water saturation capable of incorporating heterogeneous porosity fields and generalized flux functions including the water transport due to the solid phase velocity. Numerical simulations of a water-flooding problem in secondary oil recovery are presented for different realizations of the input random fields (permeability, Young modulus and initial porosity). Comparison between the accuracies of the proposed approach and the traditional one-way coupled hydro-geomechanical formulation are presented. The effects of the cross-correlation between the input random fields and compaction drive mechanism upon finger growth and breakthrough curves are also analyzed. A notable feature of the formulation proposed herein is the accurate prediction of the influence of geomechanical effects upon the unstable movement of the water front, whose evolution is dictated by rock heterogeneity and unfavorable viscosity ratio, without deteriorating the local conservative character of the numerical schemes. 相似文献
10.
以单层压实黏土衬垫为研究对象,在传统对流弥散方程的基础上考虑温度梯度下污染物的热扩散运移,得到简化条件下半无限边界的解析解。研究表明,考虑热扩散效应所得的衬垫底部相对浓度和通量均大于传统对流弥散方程所得结果,ST越大时相对浓度和通量也越大,当ST=0.5 K-1时稳定通量达到ST=0时稳定通量2.5倍。热扩散通量是对流通量的-ASTD/v倍,两者均随时间的增加而增大;分子扩散通量则先增加达到峰值后减小趋于零。同时考虑温度对运移参数的影响和热扩散效应时,温度升高使衬垫底部相对浓度增大,导致击穿时间提前,污染物通量显著增大;当温度从30℃升高至70℃时,击穿时间从8.5 a提前至5.1 a,稳定通量增大约1.7倍。在进行衬垫设计时不考虑温度的影响将使污染风险大幅增加。 相似文献
11.
This paper develops a semi-analytical solution for the transient response of an unsaturated single-layer poroviscoelastic medium with two immiscible fluids by using the Laplace transformation and the state-space method. Using the elastic–viscoelastic correspondence principle, we first introduce the Kelvin–Voigt model into Zienkiewicz’s unsaturated poroelastic model. The vibrational response for unsaturated porous material can be obtained by combining these two models and assuming that the wetting and non-wetting fluids are compressible, the solid skeleton and solid particles are viscoelastic, and the inertial and mechanical couplings are taken into account. The Laplace transformation and state-space method are used to solve the basic equations with the associated initial and boundary conditions, and the analytical solution in the Laplace domain is developed. To evaluate the responses in the time domain, Durbin’s numerical inverse Laplace transform method is used to obtain the semi-analytical solution. There are three compressional waves in porous media with two immiscible fluids. Moreover, to observe the three compressional waves clearly, we assume the two immiscible fluids are water and oil. Finally, several examples are provided to show the validity of the semi-analytical solution and to assess the influences of the viscosity coefficients and dynamic permeability coefficients on the behavior of the three compressional waves. 相似文献
12.
R. R. Yadav Dilip Kumar Jaiswal Hareesh Kumar Yadav Gulrana 《Environmental Earth Sciences》2012,65(3):849-859
A three-dimensional model for non-reactive solute transport in physically homogeneous subsurface porous media is presented.
The model involves solution of the advection-dispersion equation, which additionally considered temporally dependent dispersion.
The model also account for a uniform flow field, first-order decay which is inversely proportional to the dispersion coefficient
and retardation factor. Porous media with semi-infinite domain is considered. Initially, the space domain is not solute free.
Analytical solutions are obtained for uniform and varying pulse-type input source conditions. The governing solute transport
equation is solved analytically by employing Laplace transformation technique (LTT). The solutions are illustrated and the
behavior of solute transport may be observed for different values of retardation factor, for which simpler models that account
for solute adsorption through a retardation factor may yield a misleading assessment of solute transport in ‘‘hydrologically
sensitive’’ subsurface environments. 相似文献
13.
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
14.
Transport and deposition of suspended particles in saturated porous media: hydrodynamic effect 总被引：1，自引：1，他引：1
Nasre-Dine Ahfir Hua Qing Wang Ahmed Benamar Adbellah Alem Nicolas Massei Jean-Paul Dupont 《Hydrogeology Journal》2007,15(4):659-668
A laboratory study was undertaken to determine the transport and deposition rate of suspended particles in columns of saturated porous media (gravel and glass beads), where the porous media were subjected to steady-state flow. Silt particles with a mode of 14 μm diameter (used as the suspended particles) and fluorescein (as the conservative tracer) were injected into the columns in short pulses. The breakthrough curves were competently described with the analytical solution of a convection–dispersion equation with a first-order deposition rate. The experiments were performed using different flow rates. The suspended particle size distribution, the porous media, and the flow rates themselves were the main factors retained in this study to investigate the mechanisms governing the transport and deposition kinetics in detail. The results showed the existence of a flow rate, beyond which suspended particles travel faster than the conservative tracer. A decrease of the deposition rate of suspended particles beyond a critical flow velocity was also observed. Such behaviour led to consideration of the couple hydrodynamic-gravity forces at high flow rates. As the hydrodynamic force increases, particle deposition rates are reduced due to the effect of hydrodynamic forces inhibiting the deposition. 相似文献
15.
Numerical modelling of the dynamic process of oil displacement by water in sandstone reservoirs with random pore structures 
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下载免费PDF全文 In order to maintain the production rate of a reservoir and improve the displacement efficiency, it is crucial to have an in-depth understanding of the process of oil displacement by water. However, with respect to the conceptualization of porous media of a reservoir, very limited efforts have been made to the pore structures inside the reservoirs. In this paper, the pore structures of a sandstone reservoir were generated by using the method of random growth algorithm. Based on the randomly generated model, a theoretical model to describe the dynamic process of oil displacement by water in the sandstone reservoir was established, and then corresponding numerical modelling was performed. The effects of the displacement velocity, the viscosity ratio of oil-water phase and the porosity of reservoirs on the displacement performance were also analyzed. Results show that due to a great difference in the viscosity between oil and water phases, the moving interface of water phase is not uniform, and the viscous fingering occurs, tending to proceed along the direction with the minimum flow resistance. There is not a linear relationship between the displacement velocity and the displacement efficiency. Too high displacement velocities do not lead to much better displacement efficiency, while a higher pressure drop is caused.Choosing a proper displacement velocity is indispensable in practical engineering. A lower oil-water viscosity ratio is more favorable to obtain high displacement efficiency. Under the present simulation conditions, when the viscosity ratio is 1.2, the displacement efficiency reaches 96.2% at a moderate Reynolds number. The porosity is not a sole factor determining the displacement performance. Even for the same porosity, the shape and length of preferential flow paths are different and randomly distributed,causing a different displacement performance. A large tortuosity tends to result in a low hydraulic conductivity and displacement efficiency. 相似文献
16.
In this study, non-equilibrium transport of suspended sediment from one equilibrium state to another is investigated. Based on a convective-diffusion equation, a numerical model for flow with suspended sediment is developed by considering the effect of concentration-dependent settling velocity. The numerical model is validated by comparing analytical solutions and experimental results. The concentration profiles, mean concentrations and distance necessary to reach a new equilibrium state are examined by comparing them with the results of constant settling velocity. For a high concentration flow, the results indicate that evident differences between the above three indicators can be determined with and without concentration-dependent settling velocity. Additionally, the effects of concentration-dependent settling velocity are sensitive to the sediment mobility parameter (or Rouse number), although they are nearly independent of the diffusion Reynolds number. 相似文献
17.
This study experimentally investigates the effect of particle size, particle concentration and flow velocity on the migration of suspended particles of size 1.02–47 μm in porous media. The results show that at the same flow velocity, the peak values of the breakthrough curves decrease and corresponding pore volumes increase slightly with increasing particles size. The migration velocity of smaller suspended particles is even greater than water flow velocity, which is attributed to the size exclusion effect. With increase of the injected particle concentration, the deposition coefficients of small single particles increase at first and then tend to a steady state or even decrease slightly, explained by the maximum retention concentration. The dispersivity of small particles decreases with increasing velocity. However, at a high flow velocity, the hydrodynamic dispersivity becomes increasingly dominant with the increase of particle size. The deposition coefficients for large-sized particles are higher than those for small-sized particles, which is attributed to considerable mass removal due to straining. An analytical solution, considering the release effect of sorbed particles, is developed to account for the one-dimensional flow and dispersive effect using a source function method, and then three transport parameters—dispersivity, deposition coefficient and release coefficient—are fitted using the experimental results. Finally, suspended-particle migration is predicted by the proposed model for short-time constant-concentration injection and repeated three-pulse injection. Overall, particle size has a significant effect on the seepage migration parameters of suspended particles in porous media such as the particle velocity, dispersivity and deposition coefficient. 相似文献
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王洪涛 《吉林大学学报(地球科学版)》1991,(1)
本文介绍了地下水系统的概念和地下水系统分析方法,讨论了地下水系统模拟的驱动力场方法,推演出地下水驱动力方程和速度方程,建立了水流系统和污染质运移系统的模拟模型,并求得了它们的有限差分解,最后进行了实例模拟计算。 相似文献