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1.
A finite element method for modeling coupled flow and deformation in porous fractured media 
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下载免费PDF全文 Ahmad Pouya 《国际地质力学数值与分析法杂志》2015,39(16):1836-1852
Modeling the flow in highly fractured porous media by finite element method (FEM) has met two difficulties: mesh generation for fractured domains and a rigorous formulation of the flow problem accounting for fracture/matrix, fracture/fracture, and fracture/boundary fluid mass exchanges. Based on the recent theoretical progress for mass balance conditions in multifractured porous bodies, the governing equations for coupled flow and deformation in these bodies are first established in this paper. A weak formulation for this problem is then established allowing to build a FEM. Taking benefit from recent development of mesh‐generating tools for fractured media, this weak formulation has been implemented in a numerical code and applied to some typical problems of hydromechanical coupling in fractured porous media. It is shown that in this way, the FEM that has proved its efficiency to model hydromechanical phenomena in porous media is extended with all its performances (calculation time, couplings, and nonlinearities) to fractured porous media. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
Fushen Liu 《国际地质力学数值与分析法杂志》2020,44(12):1634-1655
The paper presents an embedded strong discontinuity approach to simulate single hydraulic fracture propagation in the poroelastic medium under plane-strain conditions. The method enriches the strain field with the discontinuous deformation mode and allows the fracture to be modeled inside elements. The Mode-I fracture initiation and propagation are described by the trilinear cohesive law, which is implemented by the penalty method. The enhanced permeability inside the fractured elements is dependent on the fracture aperture. Hydraulic fracture propagation is driven by the high pressure gradient near the fracture. Fluid transfer between the fracture and bulk rock is automatically captured within the poroelastic framework. The numerical framework is verified by the comparisons with the asymptotic analytical solutions for single hydraulic fracture propagation. 相似文献
3.
A numerical model capable of performing deformation analysis of a medium containing discontinuity surfaces is presented. The discontinuity can be either a crack, which can be open or closed, or a shear band. The model consists of two separate numerical algorithms, which are coupled together by means of the principle of superposition. In particular, an integral equation scheme based on the theory of dislocations is adopted for modelling the discontinuity, while a finite element discretization is used for the continuous medium. In this paper the discontinuity modelling is illustrated in detail, together with the specific formulation of the principle of superposition adopted, and some simple examples of application are presented. The well-known modelling approach based on Fracture Mechanics theory is also briefly discussed. The two models are compared and some advantages and drawbacks of each are pointed out, comments are made regarding their applicability in the specific case of soil mechanics, and conclusions are drawn as regards the conditions under which one or the other is appropriate. Finally, a full-scale example of deformation analysis using the proposed model is presented. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
4.
Nathan Benkemoun Hayder Al Khazraji Philippe Poullain Marta Choinska Abdelhafid Khelidj 《国际地质力学数值与分析法杂志》2018,42(3):449-468
In this paper, mesoscale hydromechanical simulations are performed to study (1) fracture features and (2) crack‐gas permeability coupling evolution in the context of the tensile splitting test. The mesostructure is based on a 2‐phase 3‐D representation of heterogeneous materials, such as concrete, where stiff aggregates are embedded into a mortar matrix. To take into account these heterogeneities without any mesh adaptation, a weak discontinuity is introduced into the strain field. In addition, a strong discontinuity is also added to take into account microcracking. This mechanical model is cast into the framework of the enhanced finite element method. Concerning the coupling with gas permeability, a double‐porosity method is used to simulate the flow through the cracks and the porosity. The apparent gas permeability is afterwards evaluated by a homogenization method. On the basis of finite element simulations, influence of aggregate size on ultimate crack opening, macroscopic ultimate tensile stress, total dissipated energy, and gas permeability evolution is numerically investigated. Furthermore, gas permeability evolution is also compared with experimental results from the literature. In addition, in the spirit of a sequential multiscale approach, macroscale gas permeability equations are identified from the hydromechanical results coming from the mesoscale computations. These equations lead to a relation between macroscale gas permeability evolution and crack opening. Besides, we show how the aggregate size influences the percolation threshold and that after this threshold, a cubic relation between macroscale gas permeability and crack opening is obtained. 相似文献
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A. M. Tartakovsky N. Trask K. Pan B. Jones W. Pan J. R. Williams 《Computational Geosciences》2016,20(4):807-834
Smoothed particle hydrodynamics (SPH) is a Lagrangian method based on a meshless discretization of partial differential equations. In this review, we present SPH discretization of the Navier-Stokes and advection-diffusion-reaction equations, implementation of various boundary conditions, and time integration of the SPH equations, and we discuss applications of the SPH method for modeling pore-scale multiphase flows and reactive transport in porous and fractured media. 相似文献
7.
A methodology is developed in SPH framework to analyze the behavior of preexisting multiple intersecting discontinuities or joints in rock material. The procedure does not require any additional unknowns to represent discontinuities and to capture velocity jump across them. Instead, a discontinuity is represented by a set of joint particles placed along the discontinuity plane, in which relative velocity and traction vector is evaluated, obeying the Mohr–Coulomb friction law with zero tension constrain. For failure of continuous rock material, the Drucker–Prager yield criterion with tensile cracking is employed in the elastic‐plastic constitutive model. Free‐sip, no‐slip, and symmetric boundary conditions are also implemented in SPH framework for proper representation of physical system. The paper analyzes behavior of a rock sample having a discontinuity plane under uniaxial loading and compares velocity and stress with a theoretical solution derived considering effective vertical stiffness of the joint planes. The efficacy of the proposed method is successfully demonstrated by solving another two problems of jointed rock mass under uniaxial and gravitational loading conditions.Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
Behnam V. Damirchi Marcelo R. Carvalho Luís A. G. Bitencourt Osvaldo L. Manzoli Daniel Dias‐da‐Costa 《国际地质力学数值与分析法杂志》2021,45(1):83-107
A new discrete fracture model is introduced to simulate the steady‐state fluid flow in discontinuous porous media. The formulation uses a multi‐layered approach to capture the effect of both longitudinal and transverse permeability of the discontinuities in the pressure distribution. The formulation allows the independent discretisation of mesh and discontinuities, which do not need to conform. Given that the formulation is developed at the element level, no additional degrees of freedom or special integration procedures are required for coupling the non‐conforming meshes. The proposed model is shown to be reliable regardless of the permeability of the discontinuity being higher or lower than the surrounding domain. Four numerical examples of increasing complexity are solved to demonstrate the efficiency and accuracy of the new technique when compared with results available in the literature. Results show that the proposed method can simulate the fluid pressure distribution in fractured porous media. Furthermore, a sensitivity analysis demonstrated the stability regarding the condition number for wide range values of the coupling parameter. 相似文献
9.
基于混合物理论孔隙-裂隙岩体的双重孔隙介质水力耦合计算的微分方程,利用伽辽金有限元法提出了相应的有限元公式,并基于岩体分类指标（RQD,RMR）提出了与岩体应变状态相关的渗透系数计算公式。编制了裂隙岩体双重介质流固耦合的2-D有限元程序,给出的验证算例表明,该程序是合理和实用的。同时将该程序用于隧道开挖的模拟计算,探讨渗流效应对开挖隧道围岩变形与渗流场的影响。计算结果表明,在隧道设计中不考虑渗流的影响是偏于不安全的。 相似文献
10.
In this paper, a fully coupled thermo-hydro-mechanical model is presented for two-phase fluid flow and heat transfer in fractured/fracturing porous media using the extended finite element method. In the fractured porous medium, the traction, heat, and mass transfer between the fracture space and the surrounding media are coupled. The wetting and nonwetting fluid phases are water and gas, which are assumed to be immiscible, and no phase-change is considered. The system of coupled equations consists of the linear momentum balance of solid phase, wetting and nonwetting fluid continuities, and thermal energy conservation. The main variables used to solve the system of equations are solid phase displacement, wetting fluid pressure, capillary pressure, and temperature. The fracture is assumed to impose the strong discontinuity in the displacement field and weak discontinuities in the fluid pressure, capillary pressure, and temperature fields. The mode I fracture propagation is employed using a cohesive fracture model. Finally, several numerical examples are solved to illustrate the capability of the proposed computational algorithm. It is shown that the effect of thermal expansion on the effective stress can influence the rate of fracture propagation and the injection pressure in hydraulic fracturing process. Moreover, the effect of thermal loading is investigated properly on fracture opening and fluids flow in unsaturated porous media, and the convective heat transfer within the fracture is captured successfully. It is shown how the proposed computational model is capable of modeling the fully coupled thermal fracture propagation in unsaturated porous media. 相似文献
11.
More sophisticated discretization methods than the traditional control-volume finite-difference methods, have been proposed by Aavatsmark et al. in recent papers for solving the mass balance equations for porous media flow. These methods are based on a local representation of fluxes across cell-edges of control volumes (CVs). This paper will focus on mathematical properties of the discrete operator that arises when an elliptic term of the form ???(K?p) is discretized based on these discretization principles. 相似文献
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通过对负指数分布模型函数的分析,推导了负指数分布的极大值函数,证明在岩体结构面实测数据的回归分析中,负指数分布存在局限性。改用双参数负指数分布作为模型函数后,能克服负指数分布的缺点,继承其优点,提高回归分析的拟合度。回归分析的方法使用最小二乘法曲线回归方法。在云南小湾水电站坝基槽边坡结构面的统计中,双参数负指数分布作为回归分析的模型函数得到了成功运用。 相似文献
13.
基于Facet模型梯度算子一致性的地震数据不连续性识别方法 总被引：1，自引：0，他引：1
存在断层、角度不整合面等不连续结构的地质体的自动识别在地震构造解释中具有重要的意义,这些地质特征的地震响应为同相轴不连续。常规的地震数据不连续性识别方法应用范围有限,参数设置依赖于人为经验,易导致识别结果辨识度差。本文将一致性作为新的不连续性识别方法引入到地震数据处理中。首先利用定位精度高、易于扩展的Facet模型梯度算子计算一致性,其次对一致性数据作阈值化处理,最后利用数学形态学中的腐蚀、膨胀及细化算法作进一步处理,实现了对地震数据不连续性信息的自动识别。经过理论和实际资料测试,并与C3相干算法和方差算法对比分析,证实了本文所提方法在地震数据不连续性识别方面具有更高的稳定性和辨识度,可以作为地层不连续性识别的有力工具。 相似文献
14.
In this paper, a numerical model is developed for the fully coupled hydro‐mechanical analysis of deformable, progressively fracturing porous media interacting with the flow of two immiscible, compressible wetting and non‐wetting pore fluids, in which the coupling between various processes is taken into account. The governing equations involving the coupled solid skeleton deformation and two‐phase fluid flow in partially saturated porous media including cohesive cracks are derived within the framework of the generalized Biot theory. The fluid flow within the crack is simulated using the Darcy law in which the permeability variation with porosity because of the cracking of the solid skeleton is accounted. The cohesive crack model is integrated into the numerical modeling by means of which the nonlinear fracture processes occurring along the fracture process zone are simulated. The solid phase displacement, the wetting phase pressure and the capillary pressure are taken as the primary variables of the three‐phase formulation. The other variables are incorporated into the model via the experimentally determined functions, which specify the relationship between the hydraulic properties of the fracturing porous medium, that is saturation, permeability and capillary pressure. The spatial discretization is implemented by employing the extended finite element method, and the time domain discretization is performed using the generalized Newmark scheme to derive the final system of fully coupled nonlinear equations of the hydro‐mechanical problem. It is illustrated that by allowing for the interaction between various processes, that is the solid skeleton deformation, the wetting and the non‐wetting pore fluid flow and the cohesive crack propagation, the effect of the presence of the geomechanical discontinuity can be completely captured. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
Fast multipole displacement discontinuity method (FM‐DDM) for geomechanics reservoir simulations 下载免费PDF全文
下载免费PDF全文 The displacement discontinuity method (DDM) is frequently used in geothermal and petroleum applications for modeling the behavior of fractures in linear‐elastic rocks. The DDM requires O(N2) memory and O(N3) floating point operations (where N is the number of unknowns) to construct the coefficient matrix and solve the linear system of equations by direct methods. Therefore, the conventional implementation of the DDM is not computationally efficient for very large systems of cracks, often limiting its application to small‐scale problems. This work presents an approach for solving large‐scale fracture problems using the fast multipole method (FMM). The approach uses both the DDM and a kernel‐independent version of the FMM along with a preconditioned generalized minimal residual algorithm to accelerate the solution of linear systems of equations using desktop computers. Using the fundamental solutions for constant displacement discontinuity in a two‐dimensional elastic medium, several numerical examples involving fracture networks representing fractured reservoirs are treated. Numerical results show good agreement with analytical solutions and demonstrate the efficiency of the FMM implementation of the DDM for large‐scale simulations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
Coupled hydromechanical‐fracture simulations of nonplanar three‐dimensional hydraulic fracture propagation 下载免费PDF全文
下载免费PDF全文 This paper presents an algorithm and a fully coupled hydromechanical‐fracture formulation for the simulation of three‐dimensional nonplanar hydraulic fracture propagation. The propagation algorithm automatically estimates the magnitude of time steps such that a regularized form of Irwin's criterion is satisfied along the predicted 3‐D fracture front at every fracture propagation step. A generalized finite element method is used for the discretization of elasticity equations governing the deformation of the rock, and a finite element method is adopted for the solution of the fluid flow equation on the basis of Poiseuille's cubic law. Adaptive mesh refinement is used for discretization error control, leading to significantly fewer degrees of freedom than available nonadaptive methods. An efficient computational scheme to handle nonlinear time‐dependent problems with adaptive mesh refinement is presented. Explicit fracture surface representations are used to avoid mapping of 3‐D solutions between generalized finite element method meshes. Examples demonstrating the accuracy, robustness, and computational efficiency of the proposed formulation, regularized Irwin's criterion, and propagation algorithm are presented. 相似文献
17.
Delfim Soares Jr. 《国际地质力学数值与分析法杂志》2014,38(4):391-405
This work proposes an iterative procedure to analyze dynamic linear/nonlinear fully saturated porous media considering time‐domain finite element discretization. In this iterative approach, each phase of the coupled problem is treated separately, uncoupling the governing equations of the model. Thus, simpler, smaller, and better conditioned systems of equations are obtained, rendering more attractive techniques. A relaxation parameter is introduced in order to improve the efficiency and robustness of the iterative solution, and an expression to compute optimal values for the relaxation parameter is discussed. At the end of the paper, numerical examples are presented, illustrating the effectiveness and potentialities of the proposed methodology. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
18.
Hydromechanical coupling in geologic processes 总被引：6，自引：2，他引：4
Earth's porous crust and the fluids within it are intimately linked through their mechanical effects on each other. This paper
presents an overview of such "hydromechanical" coupling and examines current understanding of its role in geologic processes.
An outline of the theory of hydromechanics and rheological models for geologic deformation is included to place various analytical
approaches in proper context and to provide an introduction to this broad topic for nonspecialists.
Effects of hydromechanical coupling are ubiquitous in geology, and can be local and short-lived or regional and very long-lived.
Phenomena such as deposition and erosion, tectonism, seismicity, earth tides, and barometric loading produce strains that
tend to alter fluid pressure. Resulting pressure perturbations can be dramatic, and many so-called "anomalous" pressures appear
to have been created in this manner. The effects of fluid pressure on crustal mechanics are also profound. Geologic media
deform and fail largely in response to effective stress, or total stress minus fluid pressure. As a result, fluid pressures
control compaction, decompaction, and other types of deformation, as well as jointing, shear failure, and shear slippage,
including events that generate earthquakes. By controlling deformation and failure, fluid pressures also regulate states of
stress in the upper crust.
Advances in the last 80 years, including theories of consolidation, transient groundwater flow, and poroelasticity, have been
synthesized into a reasonably complete conceptual framework for understanding and describing hydromechanical coupling. Full
coupling in two or three dimensions is described using force balance equations for deformation coupled with a mass conservation
equation for fluid flow. Fully coupled analyses allow hypothesis testing and conceptual model development. However, rigorous
application of full coupling is often difficult because (1) the rheological behavior of geologic media is complex and poorly
understood and (2) the architecture, mechanical properties and boundary conditions, and deformation history of most geologic
systems are not well known. Much of what is known about hydromechanical processes in geologic systems is derived from simpler
analyses that ignore certain aspects of solid-fluid coupling. The simplifications introduce error, but more complete analyses
usually are not warranted. Hydromechanical analyses should thus be interpreted judiciously, with an appreciation for their
limitations. Innovative approaches to hydromechanical modeling and obtaining critical data may circumvent some current limitations
and provide answers to remaining questions about crustal processes and fluid behavior in the crust.
Electronic Publication 相似文献
19.
Zekai en 《Mathematical Geology》2000,32(8):985-999
An important factor in the rock quality assessment analysis from discontinuity measurements along a scanline is the correlation of intact lengths. The autorun model and first order autorun coefficient are proposed as a method for objectively quantifying intact length correlation structure and discontinuity occurrences along any scanline. Necessary definitions for the methodology are presented on a quantitative basis such as the alternative intact length percentages and experimental autorun coefficient. An expression is proposed for the number of discontinuity occurrences along a scanline depending on the scanline length, alternate intact length percentages, and the autorun coefficient. Monte Carlo simulation technique is used with a suitable autorun model to verify this expression. A mathematical expression is derived for the expected Rock Quality Designation (RQD) value by taking into account the correlation of the intact lengths. Additional simulations show the validity of the new RQD expression. With the methodology proposed much less engineering experience and judgment are required in estimating the RQD value from scanline measurements. The application of the methodology has been presented for some field data. 相似文献
20.
The paper presents closed‐form solutions for stress and displacement influence functions for stress discontinuity (SD) and displacement discontinuity (DD) elements, for a two‐dimensional plane‐strain elastic, transversely anisotropic medium. The solutions for SD elements are based on Kelvin's problem and for DD elements on the concept of dipoles. Stress and displacement influence functions are derived for the following elements: constant SD, linear SD, constant DD, linear DD, square root DD, parabolic DD, constant DD surface, and linear DD surface elements. The formulations are incorporated into FROCK, a hybridized boundary element method code, and are validated by providing comparisons between the results from FROCK and the finite element code ABAQUS. A limited parametric analysis shows the effects of slight anisotropy on the stress field around the tip of a crack and of the orientation of the crack with respect to the axes of elastic symmetry. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献