共查询到20条相似文献，搜索用时 31 毫秒
1.
以多孔介质理论为基础,研究了稳态条件下非饱和土中温度?水分?盐分多场耦合问题。考虑非饱和土的孔隙被液态水、溶解的盐分、水蒸气和干燥气体等填充,在质量和能量守恒的基础上获得了非饱和土中水分、气体、盐分的质量守恒方程以及能量守恒方程。考虑一维稳态问题,选取温度、孔隙气压、孔隙水压和盐溶液浓度以及它们的导数作为状态变量,得到了问题的状态方程组。在给定的边界条件下,采用打靶法求解了该强耦合的非线性变系数微分方程组,通过与已有的试验结果相比较,验证了模型的有效性。基于数值算例,参数分析了含水率、温度边界、孔隙率等条件对非饱和土中温度场、水分场和盐分场分布的影响规律。 相似文献
2.
In this study, the poro-thermoelastic problem with the effect of the magnetic field and Seebeck parameter was investigated. Modified Ohm's law that includes effects of the temperature gradient (Seebeck effect) and charge density, as well as generalized Fourier's law with current density, is introduced. We applied normal mode analysis to solve the resulting nondimensional coupled equations and then investigated the effects that nondimensional displacements, temperature distribution, excess pore water pressure, stresses, and induced magnetic field exerted on the poro-thermoelastic half-space medium. Numerical analyses are given graphically on the square (2D) and cubic (3D) domains to illustrate the effects of the porosity parameter, magnetic field, and Seebeck parameter on the physical variables. 相似文献
3.
In this paper, several mechanical deformation curves of limestone are reviewed, and the effects of temperature, confining pressure, and fluid are discussed. Generally, Mohr–Coulomb is used for limestone brittle fracture. The characteristic of low temperature cataclastic flow and the conditions and constitutive equations of intracrystal plastic deformation such as dislocation creep, diffusion creep, and superplastic flow are discussed in detail. Specifically, from the macroscopic and microscopic view, inelastic compression deformation (shear-enhanced compaction) of large porosity limestone is elaborated. Compared with other mechanics models and strength equations, the dual porosity (macroporosity and microporosity) model is superior and more consistent with experimental data. Previous research has suffered from a shortage of high temperature and high pressure limestone research; we propose several suggestions to avoid this problem in the future: (1) fluid-rock interaction research; (2) mutual transition between natural conditions and laboratory research; (3) the uniform strength criterion for shear-enhanced compaction deformation; (4) test equipment; and (5) superplastic flow mechanism research. 相似文献
4.
用流固耦合方法研究油藏压裂后应力应变和孔渗特性变化 总被引：10，自引：1，他引：10
油藏压裂后将引起地应力场发生变化，使岩石变形，导致孔隙度和渗透率变化，进而影响产量，为研究这一问题，作者建立了油藏压裂后流－固耦合渗流模型，考虑了以下因素：油藏岩石变形，地应力，孔隙度和渗透率变化，人工裂缝，流体渗流与岩石应变耦合，储藏渗流与裂缝渗流耦合，非达西效应等。较详细地给出了耦合方程及推导过程，控制方程包括的未知变量有压力，饱和度及位移，11个变量，和11个方程，用有限差分方法将流体渗流和岩石应变方程离散成主对角占优的七对角矩阵，可在修改已有三维二相渗流和三维固体力学程序的基础上，采用隐式迭代方法求解，示例分析表明，用此模型可以研究储层应力变变，孔隙度和渗透率随时间和空间变化规律，为开发方案制定，整体压裂设计，压后生产管理等方面提供定量分析技术。 相似文献
5.
J. E. Smith 《Mathematical Geology》1971,3(3):239-263
A mathematical model of sedimentation and compaction of fine-grained rocks such as shale has been constructed. Water is considered to flow upward or downward out of a compacting rock according to Darcy's law until the pore-water pressure within the rock is normal for the depth in question. The porosity decreases during compaction until a minimum porosity, determined by the difference between total vertical stress (overburden pressure) and pore-water pressure, is obtained. The model takes into account the dependence of permeability on porosity for a given rock type, and the dependence of water viscosity on salinity, temperature, and pressure. The derived equations have been computer programmed to obtain the time dependence of porosity, pressure, water velocity, permeability, and other factors within a compacting shale during (a) shale sedimentation, (b) a time lapse following shale deposition, (c) the deposition of normally pressured sediments over the shale, and (d) a second time lapse following deposition of the normally pressured unit. Solutions to these problems are given for the situation when the unit underlying the shale is normally pressured, and for the situation when the underlying unit is impermeable. The calculations show that a portion of a thick shale adjacent to a normally pressured unit may have a considerably reduced porosity and permeability, and act as a seal for the remainder of the shale. High fluid pressures may persist for many millions of years in thick shales with low permeability. The computations can be extended to cover more complicated cases of interbedded shales, sands, and other lithologies. 相似文献
6.
《Tectonophysics》2001,330(1-2):141-151
In modelling sediment compaction and mineral reactions, the rheological behaviour of sediments is typically considered as poroelastic or purely viscous. In fact, compaction due to pressure solution and mechanical processes in porous media is far more complicated. A generalised model of viscoelastic compaction and the smectite to illite mineral reaction in hydrocarbon basins is presented. A one-step dehydration model of the mineral reaction is assumed. The obtained non-linear governing equations are solved numerically and different combinations of physical parameters are used to simulate realistic situations in typical sedimentary basins. Comparison of numerical simulations with real data has shown very good agreement with respect to both the porosity profile and the mineral reaction. 相似文献
7.
John M. Sharp 《Mathematical Geology》1976,8(3):305-322
Coupled energy and momentum balance equations are derived for a one-dimensional sequence of compacting sediments. These transient, nonlinear partial differential equations represent the one-dimensional equations of state for an accumulating sedimentary basin. A numerical solution is presented which provides a first-order approximation for porosity, temperature, and fluid pressures in the northern Gulf of Mexico. It seems that compaction disequilibrium is the primary mechanism for development of excess fluid pressures. Furthermore, the coupling of the equations demonstrates that temperature and pressure cannot be treated independently as may have been done in diagenetic studies. Some areas for further investigations are indicated. 相似文献
8.
The accessible porosity for Cl− in bentonite is smaller than the the total porosity due to anion repulsion (exclusion) by the surface of montmorillonite, the main mineral in bentonite. The accessible porosity is a function of the bentonite density and the salt concentration. Anion exclusion data were gathered from the literature, reprocessed in a coherent data set, and modelled using four different models. Very simple models, with or without anion access to the interlayer space, are successful in reproducing trends in anion exclusion in bentonite as a function of ionic strength in the external solution and montmorillonite bulk dry densities in the bentonite. However, a model that considers clay microstructure changes as a function of bentonite compaction and ionic strength is necessary to reproduce observed trends in the data for all experimental conditions within a single model. Our predictive model excludes anions from the interlayer space and relates the interlayer porosity to the ionic strength and the montmorillonite bulk dry density. This presentation offers a good fit for measured anion accessible porosities in bentonites over a wide range of conditions and is also in agreement with microscopic observations. 相似文献
9.
基于Fredlund非饱和土一维固结理论,建立了二维平面应变条件下的固结方程组,并得到了单层非饱和土平面应变条件下的解析解。基于相关理论,假设体变系数和渗透系数都为常量,同时考虑到瞬时加载条件下,沿着土体深度方向上产生均匀或者线性分布的初始超孔隙压力,建立了二阶二元偏微分方程组。求解时,引入函数方法来降低方程的阶数,然后通过分离变量法获得方程的通解。在此基础上,结合一个针对单面排水条件下二维平面应变问题案例,通过与数值解对比,验证了所提方法的正确性。并采用所提方法计算获得了二维平面下超孔隙水压力、气压力沿垂直和水平方向消散的等时线,通过计算对比,分析了不同线性分布情况下,初始超孔隙压力对固结消散过程的影响。研究结果表明：初始超孔隙压力的不同分布对超孔隙气压力消散的影响几乎可以忽略,而对超孔隙水压力消散的影响更大。 相似文献
10.
由于非饱和土的渗透系数是基质吸力的函数,使得控制方程带有强非线性的特征,进而使得控制方程的解析求解变得十分困难。同伦分析法对级数基函数和辅助线性算子的选择具有更大的自由性、灵活性,且收敛性的控制和调节更加容易实现,求解强非线性微分方程时在选择线性算子以及辅助参数上具有明显的优势。因此,针对非饱和土固结方程的非线性特征,对于处于地表浅层的非饱和土层,假设孔隙气压力为大气压力,在Richard经验公式与非饱和土一维固结理论的基础上,推导了非饱和一维固结无量纲控制方程;应用同伦分析法,通过选取适当的初始猜测解与辅助参数,将该非线性方程转换为线性的微分方程组并求解得到固结问题的级数解。此外,以压实高岭土为研究对象,在收集相关试验参数基础之上,将由同伦分析法求得的固结问题的近似解析解与有限差分法数值结果相对比,分析结果验证了解析解的正确性。 相似文献
11.
Anion exclusion effects in compacted bentonites: Towards a better understanding of anion diffusion 总被引：1，自引：0，他引：1
Diffusion of 36Cl− in compacted bentonite was studied using through-diffusion, out-diffusion and profile analysis techniques. Both the bulk dry density of the bentonite and the composition of the external solution were varied. Increasing the bulk dry density of the bentonite resulted in a decrease of both the effective diffusion coefficient and the Cl-accessible porosity. Increasing the ionic strength of the external solutions resulted in an increase of both the effective diffusion coefficient and the Cl-accessible porosity. This can be explained by anion exclusion effects (Donnan exclusion). At high ionic strength values (I ? 1 M NaCl) the Cl-accessible porosity approaches the interparticle porosity. This interparticle porosity is the difference between the total and interlayer porosity of the bentonite. The interlayer porosity was found to depend on the degree of compaction. Up to a bulk dry density of 1300 kg m−3 the interlayer is built up of 3 water layers. Between 1300 and 1800 kg m−3 the interlayer water is reduced from 3 to 2 layers of water. Above 1800 kg m−3 evidence for a further decrease to 1 layer of water was found. These findings are in agreement with X-ray data found in the literature showing a decrease of the basal spacing of montmorillonite (the main clay mineral in bentonite) with increasing degree of compaction. The relationship between the effective diffusion coefficient of Cl− and the diffusion-accessible porosity can be described by an empirical relationship analogous to Archie’s law. To predict the effective diffusion coefficient of Cl− in compacted bentonite, the diffusion coefficient of Cl− in water, the bulk dry density and the ionic strength of the pore water have to be known. 相似文献
12.
Emad S. AlHomadhi 《Arabian Journal of Geosciences》2014,7(7):2871-2879
In sandstone, there is a trend between porosity (?) and permeability (k). It is a linear relationship having the form log (k)?=?a?+?(b ?). The slope, intercept, and degree of scatter of the log(k)???? trends vary from formation to another. These variations are attributed to differences in initial grain size and sorting, diagenetic history, cementation, clay content, pore geometry, and compaction history. In the literature, permeability and porosity modeling by using lab experiments was carried out by using unconsolidated sandstone, sand packs, or synthetic particles. Such models cannot be applied to predict flow properties of consolidated natural sandstone. Furthermore in these models, sand grain size, shape, and sorting factors were considered as the main factors that affect porosity and permeability. Hardly, any attention was paid to the confining pressure and the fraction of cementing material that bind the grain to form a coherent rock. If these two crucial aspects are not taken into consideration during the model development, the model cannot be applied to natural consolidated sandstone. The main objective of the present paper is to develop a new model for porosity versus permeability taking into account important factors such as sand grain size and sorting, compaction pressure, and concentration of cementing material that bind the sand grains. The effect for clay swelling or migration was however discarded, as the sand grains were washed prior to consolidation. The sand used in producing the sandstone cores was medium- to fine-sized well-sorted sand grains. The grain’s sphericity was measured to be in the range of (0.8–0.9) with little angularity. The fabricated cores have an average compressive strength of 5,700 psi, which is comparable with Bera sandstone strength. Also, the produced cores were stable in the fluid media as they were subjected to 300 °C to allow cementing material to be crystallized. The aspect of the present work was to analyze the dependence of both the permeability as well as the porosity on the variables of the present study that consist of grain size, cementation fraction, and the confining pressure. Using the experimental data, a linear relationship, in terms of each variable, was developed here that can eventually help researchers to fabricate cores with desired properties. The second step was to generate more general models to be used as references for scholars for further work in this research field. Nonlinear regression analysis was carried out on all the three variables of the present study to obtain two nonlinear correlations: one describes the behavior of permeability and the other describes porosity. In the third step, an advanced correlation that describes permeability versus porosity in a quantitative manner was developed by using nonlinear regression analysis. Permeability was studied accordingly as a function of all the three variables of the present study as well as porosity. This step represents the main objective of this paper. 相似文献
13.
吐哈盆地巴喀气田八道湾组致密砂岩储层分析及孔隙度演化定量模拟 总被引：1，自引：0，他引：1
在吐哈盆地巴喀气田八道湾组砂岩储层特征及控制因素分析的基础上,以地史时间和埋藏深度为变量,以现今孔隙度为约束条件,紧密结合埋藏阶段分析和关键成岩阶段窗口分析,分阶段建立了巴喀气田八道湾组储层从埋藏初始直至现今的孔隙度演化定量模型,动态体现了整个孔隙度演化过程。定量模拟结果表明：研究区储层总孔隙度演化是一个七段式分段函数,各个阶段孔隙度演化或遵循减小模型或遵循减小与增大的叠加模型;机械压实阶段的孔隙度减小模型是以埋深为自变量的函数,压实和胶结综合作用阶段则是以埋深和埋藏时间为变量的函数;孔隙增大模型适用于Ro值范围为0.6～1.0的溶蚀作用窗口内;早期的纯机械压实作用使八道湾组储层已接近致密,溶蚀作用之前的压实和胶结综合作用导致储层致密化,而后期溶蚀作用仅在一定程度上提高了孔隙空间。 相似文献
14.
对渗透各向异性土层中的圆形围堰渗流场进行解析研究。将圆形围堰周围渗流场分为3个区域,通过坐标变换以及将边界条件齐次化后,用分离变量法分别得到柱坐标系下3个区域的水头分布级数解形式,结合区域间的连续条件,并利用贝塞尔函数正交性得到渗透各向异性土层中圆形围堰稳态渗流场的显式解析解,与Plaxis2D软件的计算结果进行对比,验证了解析解的正确性。基于解析解,进一步推导出了涌水量、出逸比降公式,并与不同方法的计算结果作了对比,最后对稳态渗流情况下的水压力进行了计算分析。结果表明：相比于其他近似法,解析解求取的流量、出逸比降以及渗流情况下水压力与数值计算结果高度吻合;渗流水压力会随着围堰半径、纵横向渗透系数比值的增大而减小,而后逐渐趋近于一个稳定值。 相似文献
15.
Novel basin modelling concept for simulating deformation from mechanical compaction using level sets
Sean McGovern Stefan Kollet Claudius M. Bürger Ronnie L. Schwede Olaf G. Podlaha 《Computational Geosciences》2017,21(5-6):835-848
As sedimentation progresses in the formation and evolution of a depositional geologic basin, the rock strata are subject to various stresses. With increasing lithostatic pressure, compressional forces act to compact the porous rock matrix, leading to overpressure buildup, changes in the fluid pore pressure and fluid flow. In the context of petroleum systems modelling, the present study concerns the geometry changes that a compacting basin experiences subject to deposition. The purpose is to track the positions of the rock layer interfaces as compaction occurs. To handle the challenge of potentially large geometry deformations, a new modelling concept is proposed that couples the pore pressure equation with a level set method to determine the movement of lithostratigraphic interfaces. The level set method propagates an interface according to a prescribed speed. The coupling term for the pore pressure and level-set equations consists of this speed function, which is dependent on the compaction law. The two primary features of this approach are the simplicity of the grid and the flexibility of the speed function. A first evaluation of the model concept is presented based on an implementation for one spatial dimension accounting for vertical effective stress. Isothermal conditions with a constant fluid density and viscosity were assumed. The accuracy of the implemented numerical solution for the case of a single stratigraphic unit with a linear compaction law was compared to the available analytical solution [38]. The multi-layer setup and the nonlinear case were tested for plausibility. 相似文献
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济阳坳陷古近系深部储层成岩演化模式 总被引：4，自引：0，他引：4
运用岩石薄片鉴定、扫描电镜分析、镜质体反射率分析、X-衍射分析和油层物性分析等手段,结合区域油气地质研究成果,以揭示济阳坳陷古近系深部碎屑岩储层的成岩演化模式和物性演化规律为目的开展工作。结果表明,济阳坳陷古近系深部碎屑岩储层主要受其所处构造背景、地层压力和流体环境的影响,发育6种成岩演化模式。弱陡坡/缓坡构造背景条件下发育早期中强超压-中强压实/胶结/溶蚀-多重介质成岩演化模式和晚期中强超压-（较）强压实/胶结/溶蚀-酸性介质成岩演化模式,超压形成的早晚是影响储层压实作用强弱的主要因素,而流体环境的差异与构造背景的差异有关。深洼陷发育弱超压/常压-（中）强压实/胶结-强溶蚀-热液酸性介质成岩演化模式和中弱超压-较强压实/胶结-强溶蚀-热液酸性介质成岩演化模式,热液活动加强了成岩流体对酸溶性组分的溶解,是该类成岩演化模式的主要影响因素。处于陡坡常压条件下的深层碎屑岩发育（中）强压实/胶结-弱溶蚀-热液酸性介质和强胶结-中弱溶蚀-多重介质成岩演化模式,早期沉积水体、后期成岩水体以及两者混合造成的多重介质是其主要影响因素。综合分析认为,层位和埋深是深部储层遭受成岩改造程度强弱的首要控制因素;构造位置是影响成岩压力场和流体场的基本前提;在不同的流体场背景中,深部热液对储层演化会不同影响;酸碱交替的多重成岩环境增加了次生孔隙带发育个数和次生孔隙垂向分布,但原始孔隙度保存率比以酸性介质为主的成岩环境低5%以上。 相似文献
19.
构造-流体-成矿体系的反应-输运-力学耦合模型和动力学模拟 总被引：12，自引：0，他引：12
建立了一个综合的构造流体成矿体系的反应输运力学耦合动力学模型。利用有限元方法求解岩石变形、断裂作用和断裂网络统计动力学、流体流动、有机和无机地球化学反应及成岩成矿作用、压力溶液和其它压实力学、热迁移的方程组 ,可以对构造流体成矿体系的动力学演化过程进行 1～ 3维数值模拟。模拟的主要内容是在各种过程耦合作用下描述构造流体成矿体系的主要变量的时空演化 :( 1)与成矿流体的形成和性质有关的变量 ,如地层中矿物 (包括成矿物质 )的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等 ;( 2 )与构造变形和流体运移有关的各变量 ,如应力与变形速率、岩石孔隙度、构造 (断裂 )渗透率等 ;( 3 )与沉淀成矿有关的变量 ,如矿物 (金属矿物和脉石矿物 )的成核速率、各矿物的沉淀量等 ;( 4 )上述各有关变量间的时空耦合关系 ,如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。以湖南沃溪金锑钨矿床为例 ,应用该模型和方法对成矿动力学过程和动力学机制进行了初步的模拟与分析。 相似文献