汾渭盆地地裂缝成因研究中的若干关键问题

汾渭盆地是我国地裂缝发育最强烈的地区,地裂缝类型多样,成因复杂。本文概述了汾渭盆地地裂缝的分布规律,分析了目前汾渭盆地地裂缝成因研究中存在的主要问题,重点围绕构造型地裂缝的成因问题,提出如下研究思路:通过多学科联合手段,重点研究汾渭盆地地裂缝灾害的分布规律及其与活动构造的分布关系与成生联系,建立构造地裂缝的地质结构模型;将现代物理数值模拟技术与高精度观测技术相结合,分析研究构造活动启动地裂缝灾害的力学机理以及构造作用与抽水作用耦合致裂机理;以GPS观测资料为约束,将汾渭盆地地裂缝的成生与青藏、华北大陆变形的动力学过程联系起来,研究该区地裂缝与现今中国大陆动力学的内在联系,揭示大陆驱动力产生地质灾害的动力学机制与模式。     

松辽盆地咸含水层埋存CO2储存容量初步估算

沉积盆地深部存在体积巨大的咸含水层,是很好的埋存CO2的地质储体。可靠合理的估计CO2储存容量是选择场址的重要前提。目前国际上较为通用的评价CO2储存容量是金字塔评价方法。松辽盆地咸含水层岩性以白垩系的嫩江组砂岩和青山口组砂岩为主,空隙发育较好,盖层连续完整且封闭良好,决定了其可以作为储存CO2的地质储体。以松辽盆地为实例,估算了咸含水层CO2理论储存容量大约为6916Gt。     

Characteristic finite difference method and application for moving boundary value problem of coupled system

The coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution.It is of great value in rational evaluation of prospecting and exploiting oil-gas resources.The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values.A kind of characteristic finite difference schemes is put forward,from which optimal order estimates in l^2 norm are derived for the error in the approximate solutions.The research is important both theoretically and practically for the model analysis in the field,the model numerical method and software development.     

磨西河流域泥石流流域形态的非线性特征

泥石流是磨西河流域地质环境演化的一个重要地表过程,研究该流域内泥石流的地貌发育及演化特征可为磨西河流域第四纪以来地质环境的演变提供重要信息。通过对流域51条泥石流沟地貌形态的统计分析发现,磨西河流域内泥石流的分布在空间上表现出明显的不均性,流域内泥石流沟的数量与对应的主沟长度、主沟纵比降及流域面积之间存在着明显的分形现象,具有较高的自相似性。结果表明,泥石流沟谷形态的非线性演化特征及现象是对磨西河流域冰川环境和地质构造环境响应的直接结果,主要体现在现代冰川对流域的强烈侵蚀和贡嘎山隆升而导致流域的强烈下切。研究结果可为流域内泥石流灾害的形成机理、防灾减灾及流域环境演化提供理论依据。     

Numerical simulation analysis for migration-accumulation of oil and water

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Upwind finite difference method for miscible oil and water displacement problem with moving boundary values

The research of the miscible oil and water displacement problem with moving boundary values is of great value to the history of oil-gas transport and accumulation in the basin evolution as well as to the rational evaluation in prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. For the twodimensional bounded region, the upwind finite difference schemes are proposed. Some techniques, such as the calculus of variations, the change of variables, and the theory of a priori estimates, are used. The optimal orderl2-norm estimates are derived for the errors in the approximate solutions. The research is important both theoretically and practically for the model analysis in the field, the model numerical method, and the software development.     

Free tides in two-dimensional uniform-depth basins

The problem of free tidal wave propagation in two-dimensional uniform-depth basins is considered. To solve the problem, a numerical algorithm, a version of the Babenko method, is developed. The algorithm makes it possible to solve the problem in a singly-connected domain admitting conformal mapping onto a circle. A solution can be obtained for both nonrotating and rotating basins. The first natural frequencies are determined for elliptic basins with different eccentricities and angular velocities and certain characteristic natural shapes demonstrating the distinctive features of tidal flows in elliptic basins are constructed. The time evolution of modes in a rotating elliptic basin is studied.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 119–130. Original Russian Text Copyright © 2004 by Ivanov.     

Free Fluid Flow Through a Visco-Deformable Porous Medium with a Moving Boundary

One-dimensional Darcy-law flow through a porous matrix representing a high-viscosity liquid is investigated. The flow develops in a region which depends on time due to sedimentation. The problem considered simulates the geological process of sedimentation in a basin. In accordance with geological data, the permeability and viscosity coefficients of the matrix are assumed to depend nonlinearly on the porosity. The asymptotic properties of the flow are described for large times. The agreement between the results of asymptotic and numerical solutions is satisfactory at intermediate times and good at large times under the realistic sedimentary basin conditions. The simplicity of the asymptotic solution obtained makes it possible to vary the problem parameters and determine the porosity, pressure, and velocities for particular geological conditions by means of simple calculations.     

New hybrid Cartesian cut cell/enriched multipoint flux approximation approach for modelling and quantification of structural uncertainties in petroleum reservoirs

Efficient and profitable oil production is subject to make reliable predictions about reservoir performance. However, restricted knowledge about reservoir rock and fluid properties and its geometrical structure calls for history matching in which the reservoir model is calibrated to emulate the field observed history. Such an inverse problem yields multiple history‐matched models, which might result in different predictions of reservoir performance. Uncertainty quantification narrows down the model uncertainties and boosts the model reliability for the forecasts of future reservoir behaviour. Conventional approaches of uncertainty quantification ignore large‐scale uncertainties related to reservoir structure, while structural uncertainties can influence the reservoir forecasts more significantly compared with petrophysical uncertainty. Quantification of structural uncertainty has been usually considered impracticable because of the need for global regridding at each step of history matching process. To resolve this obstacle, we develop an efficient methodology based on Cartesian cut cell method that decouples the model from its representation onto the grid and allows uncertain structures to be varied as a part of history matching process. Reduced numerical accuracy due to cell degeneracies in the vicinity of geological structures is adequately compensated with an enhanced scheme of a class of locally conservative flux continuous methods (extended enriched multipoint flux approximation method or extended EMPFA). The robustness and consistency of the proposed hybrid Cartesian cut cell/extended EMPFA approach are demonstrated in terms of true representation of geological structures influence on flow behaviour. Significant improvements in the quality of reservoir recovery forecasts and reservoir volume estimation are presented for synthetic model of uncertain structures. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulation and application of three-dimensional migration-accumulation of oil resources

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Wada分形吸引域边界上的混沌鞍

应用广义胞映射图论（Generalized Cell Mapping Digraph)方法，数值地研究Thompson的逃逸方程在最佳逃逸点附近的分岔。发现了嵌入在Wada分形吸引域边界上的混沌鞍，混沌鞍是状态空间不稳定（非吸引）的混沌不变集合。Wada分形吸引域边界是具有Wada性质的边界，即吸引域边界上的任意点也同时是至少两个其它吸引域的边界点，称为Wada域边界。我们证明Wada域边界上的混沌鞍导致局部鞍结分岔具有全局不确定性结局，研究了Wada域边界上混沌鞍的形成与演化，证明最终的逃逸分岔是混沌吸引子碰撞混沌鞍的边界激变。     

二维洪水演进数值模拟

利用非结构化的有限体积方法,建立了二维浅水方程高精度、高分辨率模型。以Roe类型的近似Rie-mann解计算界面通量,通过MUSCL和两步TVD Runge-Kutta法获得了空间和时间都具有二级精度的TVD格式。采用特征分解的方法处理底坡源项和采用半隐式方法处理摩擦源项均能保证了格式的稳定性与和谐性。通过水滴算例对模型进行验证,并应用此模型对98年胖头泡分滞洪区分洪过程进行模拟,获得滞洪区不同时段的淹没范围和淹没水深,为防洪救灾提供了依据。     

多稳态串联折纸结构的非线性动力学特性

折纸结构和折纸力学超材料由于其无穷的设计空间、出色的变形能力、超常规力学特性和广泛的应用前景,最近受到了学术界和工程界的 广泛关注.特别地,某些折纸结构单胞由于具有独特的双稳态特性而获得深入研究.注意到折纸结构和折纸超材料通常由多胞构成,但多胞 结构的多稳态特性及其诱发的动力学行为尚不清晰,相关的研究还较少.本文在双稳态Miura-ori堆叠结构单胞的基础上,研究由两个异构 双稳态单胞基于力平衡串联而成的结构.静力学分析指出,双胞串联结构具有4个定性不同的稳定构型,呈现出多稳态特征.动力学分析指 出,双胞串联结构在4个稳定构型处具有显著不同的固有频率特征. 逐渐增大激励幅值,双胞串联结构的多稳态特性诱发出类型丰富的复杂 非线性动力学响应,包括亚谐、超谐甚至混沌的阱内和阱间振动. 根据幅值特征,我们将稳态动力学响应分为九类,并开展了动力学响应的 吸引盆和吸引盆稳定性分析.结果表明,不同类型动力学响应的吸引盆稳定性(即出现概率)显著不同,且与激励幅值密切相关.本文得到的 多稳态双胞串联结构的静力学特性、动力学响应的分类,以及吸引盆稳定性相对于激励幅值的演化规律,对深入认识多稳态折纸结构的非 线性动力学特性,调控非线性动力学响应具有参考价值和指导意义.      

Analytical and numerical studies for Seiches in a closed basin with bottom friction

A standing wave oscillation in a closed basin, known as a seiche, could cause destruction when its period matches the period of another wave generated by external forces such as wind, quakes, or abrupt changes in atmospheric pressure. It is due to the resonance phenomena that allow waves to have higher amplitude and greater energy, resulting in damages around the area. One condition that might restrict the resonance from occurring is when the bottom friction is present. Therefore, a modified mathematical model based on the shallow water equations will be used in this paper to investigate resonance phenomena in closed basins and to analyze the effects of bottom friction on the phenomena. The study will be conducted for several closed basin shapes. The model will be solved analytically and numerically in order to determine the natural resonant period of the basin, which is the period that can generate a resonance. The computational scheme proposed to solve the model is developed using the staggered grid finite volume method. The numerical scheme will be validated by comparing its results with the analytical solutions. As a result of the comparison, a rather excellent compatibility between the two results is achieved. Furthermore, the impacts that the friction coefficient has on the resonance phenomena are evaluated. It is observed that in the prevention of resonances, the bottom friction provides the best performance in the rectangular type while functioning the least efficient in the triangular basin. In addition, non-linearity effect as one of other factors that provide wave restriction is also considered and studied to compare its effect with the bottom friction effect on preventing resonance.     

Domain decomposition for an asymptotic geological fault modeling

We present in this paper a domain decomposition method to treat faults in geological basin modeling. The particularity of this model is that the faults whose widths are very small in comparison with the basin size, are not characterized as subdomains any more but as interfaces between sedimentary blocks. The originality of this work lies in the formulation of this new fault model and in the definition and the computation of the interface conditions between the subdomains. To cite this article: E. Flauraud et al., C. R. Mecanique 331 (2003).     

Discrete numerical investigation of the ratcheting phenomenon in granular materials

Several relevant geotechnical works, such as railway and road embankments, offshore foundations and vibrating machine foundations, are affected by the progressive accumulation of irreversible settlements. These latter represent the macroscopic evidence of the progressive rearrangement of particles under cycling loading, which is commonly referred to, in the literature, as ratcheting. This phenomenon is well known, but it is quite difficult to describe it by means of an appropriate constitutive model. As a consequence, the evaluation of durability of the aforementioned structures remains an open problem. In this article, the phenomenon will be approached by employing a Distinct Element model capable of describing the evolution of the microstructure induced by cyclic mechanical perturbations. Several analyses are performed in order to stress the influence of both the stress level and loading history on the mechanical response of a numerical model of a sand specimen. The numerical analyses are intended to provide an experimental background for conceiving a simplified macro approach based on generalised plasticity theory. In particular by means of probe test the plastic potential and the hardening parameters will be defined as a function of the current stress state and loading history.     

CAD软件在工程地质三维建模中的应用

如何快速、准确地建立地质体的三维模型一直是众多岩土工程数值模拟工作者所面临的难题。虽然三维地学模拟软件具有很好的三维地质建模能力,但是由于数据结构的差异,采用他们现行三维地学模拟软件建立的地质模型难以导入数值模拟分析软件中,以为相应工程问题的数值模拟服务。目前,随着各种CAD、CAM软件行业的的飞速发展,涌现出了许多优秀的三维建模软件,而且这些软件大都与现行数值分析软件有着良好的数据接口功能。据此,本文提出了采用现行CAD软件来建立工程地质体的三维模型,使得建立的模型达到既"可视"又"可算"的目的。将其应用于云南某高速公路边坡的三维建模中,证明了该法具有方便、快捷和合理等优点。     

Repository-Scale Modeling of the Long-Term Hydraulic Perturbation Induced by Gas and Heat Generation in a Geological Repository for High-and Intermediate-Level Radioactive Waste: Methodology and Example of Application

The current design of a deep geological repository for high- and intermediate-level radioactive waste in France consists of a complex system of different underground structures (ANDRA, Dossier 2005 Argile, les recherches de l’Andra sur le stockage géologique des déchets radioactifs à haute activité et à vie longue, collection les Rapports. Chatenay-Malabry, France, 2005). For a comprehensive understanding of the long-term hydraulic evolution of the entire repository, numerical non-isothermal two-phase flow and transport simulation, taking into consideration the generation, accumulation, and release of hydrogen gas and decay heat, are compulsory. However, a detailed numerical model of the entire repository system would require a tremendous computational effort and pose a laborious task with respect to the operation of the model. To handle these difficulties, we have developed an efficient method for the numerical modeling of a complete repository system and its geologic environment. The method consists of the following steps: (i) subdivision of the repository plane into a large number of “sectors” based on the position of hydraulic seals and on other geometrical considerations, (ii) exploitation of existing symmetries (inside or between sectors), (iii) adoption of the “multiplying concept”, and (iv) connection of the individual sectors at the drift interfaces to form the entire repository model. Each sector is modeled as a three-dimensional (3D) block, and the entire model is computed with TOUGH2-MP. The method allows for a massive reduction in overall finite-volume elements and, at the same time, provides an adequate representation of the small-sized structures in the repository. The main characteristics of the method and its application to an entire deep geological repository system in a clay host rock are presented.     

Micro-sphere model for strain-induced crystallisation and three-dimensional applications

Strain-crystallising rubber exhibits interesting properties: for instance, fatigue lifetime is known to be modified by this microstructural evolution which dissipates energy and creates a strong anisotropic reinforcement. We develop herein a micro-sphere 3D constitutive model for such strain-crystallising rubber. It is based on a simplified 1D micromechanical model that we extend with a micro-sphere approach to a full thermodynamically consistent evolutive anisotropic model. A specific numerical strategy is then proposed. The model is assessed on several significative configurations and reproduces the main experimental features while predicting the evolution of anisotropy as a function of the loading history. We finally show that it can also predict the crystallised zone in front of a mode I crack.     

Multiresolution Wavelet Scale Up of Unstable Miscible Displacements in Flow Through Heterogeneous Porous Media

We describe scale up of geological models of field-scale porous media using a new method based on the wavelet transformations. The porous media of interest contain broadly-distributed and correlated permeabilities. Wavelet transformation of the permeability field of such porous media coarsens the geological model from smallest to largest length scales, drastically reduces the number of equations to be solved, preserves the important information on the permeability field at all the relevant length scales, and yields numerical results for any fluid flow property that are as accurate as those that are obtained with the highly detailed geological model of the same porous media. To test this method, we carry out extensive computer simulations of unstable miscible displacement processes and the associated viscous fingering phenomenon in highly heterogeneous porous media, both with the fine-scale geological model and the coarsened model. Excellent agreement is found between the results of the two sets of simulations.