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本文系统地介绍了多点地质统计学的基本原理及方法，并以我国渤海湾盆地某区块新近系明化镇组河流相储层为例，进行了多点统计学随机建模的实例分析。多点地质统计学为储层随机建模的国际前沿研究方向，该方法综合了基于象元的方法易忠实条件数据以及基于目标的方法易再现目标几何形态的优点，同时克服了传统基于变差函数的二点统计学不能表达复杂空间结构和再现目标几何形态的不足。通过理论与实例研究，分析了目前多点统计学尚存在的问题(包括训练图像平稳性问题、目标连续性问题以及综合软信息的问题等)及未来发展的方向。 相似文献
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Linda Werner Hartman 《Mathematical Geology》2006,38(2):113-133
Spatial datasets are common in the environmental sciences. In this study we suggest a hierarchical model for a spatial stochastic field. The main focus of this article is to approximate a stochastic field with a Gaussian Markov Random Field (GMRF) to exploit computational advantages of the Markov field, concerning predictions, etc. The variation of the stochastic field is modelled as a linear trend plus microvariation in the form of a GMRF defined on a lattice. To estimate model parameters we adopt a Bayesian perspective, and use Monte Carlo integration with samples from Markov Chain simulations. Our methods does not demand lattice, or near-lattice data, but are developed for a general spatial data-set, leaving the lattice to be specified by the modeller. The model selection problem that comes with the artificial grid is in this article addressed with cross-validation, but we also suggest other alternatives. From the application of the methods to a data set of elemental composition of forest soil, we obtained predictive distributions at arbitrary locations as well as estimates of model parameters. 相似文献
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随机模拟和随机反演是两种比较常用的较精细的储层预测方法,而变差函数是随机模拟、随机反演的核心技术。以喇嘛甸油田北北二区块SⅢ层段为研究对象,选用300 m×300 m、600 m×600 m、800 m×800 m、1 200 m×1 200 m不同变程变差函数,对随机模拟和随机反演结果对比分析,探讨不同变程对预测结果的影响。结果显示：随着变程的增大,随机模拟砂体结果由离散发展成连续片状分布,而随机反演砂体分布整体趋势一致,只有局部薄层砂体受到较小程度的影响;通过盲井验证,随机反演较随机模拟,其预测的砂体与井点的符合率更高。分析认为,随机反演较随机模拟多了井间地震的约束,减少了砂体分布的不确定性和多解性,提高了井间砂体的预测精度,便于在油田开发阶段推广应用。 相似文献
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以基坑工程为例分析了开挖损伤演变的模糊随机性并建立了广义非确定性空间O：Б（s,f）。提出了初始损伤有效张量的概念模型,在“损伤源汇”概念基础上提出了模糊衰减模型,构造了粘塑性模糊随机损伤增量方程并实现了基坑开挖过程的模糊随机损伤模拟。在线性算子基础上提出了模糊随机损伤矢量极限值{Ωu},进而建立了以损伤有效张量为基础的粘塑性模糊随机损伤本构模型及粘塑性非线性模糊随机数值方法。在粘塑性模糊随机损伤有限元基础上建立了粘塑性模糊随机损伤变化率方程,实现了对基坑开挖过程中模糊随机损伤演变发展的全面模拟,完成了模糊随机卸荷损伤模型的构建。 相似文献
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A. B. Vistelius 《Mathematical Geology》1987,19(7):589-612
A definition of the ideal granite and its metasomatic transformation are discussed and the corresponding matrices of transition probabilities are given, along with guidelines for accepting models. Some results are presented using these models to examine granitic massifs and to search for high-temperature ore deposits. Current problems in investigation of granitic massifs on the basis of stochastic models are reviewed. 相似文献
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Natural Hazards - The Ya’an, Sichuan Mw 6.7 earthquake occurred on April 20, 2013. In this article, the stochastic finite-fault method (EXSIM) based on dynamic corner frequency, proposed by... 相似文献
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A new perturbation technique and finite-element method, which incorporates an undetermined-coefficients approach, is proposed to conduct stochastic simulation for problems of groundwater flow. Formulas of the mean value and variance of groundwater head are derived to exclude the process of computing the first and second-order derivatives of groundwater head with respect to stochastic variables (coefficient of transmissibility, storage coefficient, etc.) in the calculation process of common finite element methods. For ordinary stochastic groundwater problems, the statistical properties of groundwater head can be easily obtained by using the proposed method, which is especially efficient for the stochastic problems that have fewer input stochastic variables. A stochastic numerical simulation of a two-dimensional confined-groundwater flow problem has been conducted to validate effectiveness and determine the limitations of the proposed method. The results illustrate that the accuracy and efficiency of the method proposed are satisfactory, and that the computing time is shorter when there is a small number of input stochastic variables. 相似文献
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探讨了综合应用地质及测井约束地震反演信息进行三维沉积微相随机建模的基本原理、思路与方法，并以渤海湾盆地某区块新近系明化镇组河流相储层为例，说明这一研究过程的基本步骤，包括井眼沉积微相解释、测井约束地震反演、波阻抗与地质相的概率关系分析、随机模拟方法选择、地质统计特征分析、三维随机建模、随机模拟预测的多解性评价。研究表明，波阻抗与沉积微相之间具有一定的概率相关关系。综合应用包括地震信息在内的多学科信息进行沉积微相随机建模，可对储层预测的多解性进行有效评价。 相似文献
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Natural Hazards - Time series studies depend mostly on stochastic models for radon seasonal, annual or temporal variability explanations. Others solve radon transport steady state equation... 相似文献
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We consider a spatial stochastic model for the simulation of tropical cyclone tracks, which has recently been introduced. Cyclone tracks are represented as labeled polygonal lines, which are described by the movement directions, translational speeds, and wind speeds of the cyclones in regular 6-h intervals. In the present paper, we compare return levels for wind speeds of historically observed cyclone tracks with those generated by the simulator, where a mismatch is shown for most of the considered coastal regions. To adjust this discrepancy, we develop a stochastic algorithm for acceptance and rejection of simulated cyclone tracks with landfall. It is based on the fact that the locations, translational speeds, and wind speeds of cyclones at landfall constitute three-dimensional Poisson point processes, which are a basic model type in stochastic geometry. Due to that, a well-known thinning property of Poisson processes can be applied. This means that to each simulated cyclone, an acceptance probability is assigned, which is higher for cyclones with suitable landfall characteristics and lower for implausible ones. More intuitively, the algorithm comprises the simulation of a more comprehensive cyclone event set than needed and the random selection of those tracks that best match historical observations at landfall. A particular advantage of our algorithm is its applicability to multiple landfalls, i.e., to cyclones that successively make landfall at two geographically distinct coastlines, which is the most relevant case in applications. It turns out that the extended simulator provides a much better accordance between landfall characteristics of historical and simulated cyclone tracks. 相似文献
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本文从最大后验概率密度观点出发，在数据噪音向量和待求模型向量为具有零均值的独立高斯随机过程的假设前提下，建立起了随机反演的非线性系统方程；给出了模型方差估计的函数表达式，并在文章最后，证明了反演解的稀疏性，即解释了随机反演的输出解的高分辨率特征。文章在最小二乘反演方法的基础上，发展并完善了随机反演方法的理论基础；揭示了随机反演方法与最小二乘反演方法之间的本质区别；阐述了随机反演方法的优越性，并指出了其广阔的应用前景。 相似文献
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地下水模型的Neumann展开Monte-Carlo随机有限元法 总被引：1，自引：0，他引：1
讨论了求解地下水模型(水流模型和水质模型)的Neumann展开Monte-Carlo随机有限元法。从基本的随机变量入手,避免了过程中随机变量的增多问题,给出结点水头(浓度)的均值、方差和水头在某区间的概率计算方法;改进了矩阵求逆的效率,对输入随机变量较多、随机变量变异较大的非稳定地下水问题特别有效。同时选取二维承压地下水水流问题(有解析解)作为例子,进行了随机数值模拟实验。 相似文献
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为了探究水文地质结构对地下水流数值模拟的不确定性,可以运用随机模拟建立地下水位的预测模型。根据转移概率地质统计方法模拟多孔介质岩性分布,利用非线性规划的思路计算岩性与水文地质参数之间的关系,从而建立相对精确的随机水文地质参数场。将不同的水文地质参数场运用到MODFLOW中,得到不同的随机模拟结果。通过比较随机模型和确定模型的末流场拟合情况以及水位动态拟合图,发现确定模型和随机模型具有相似趋势,都能与实测流场拟合较好,但是随机模型更能体现真实的水文地质特征。对随机模型预测10年后的地下水水位做不确定性分析,得到水位平均变幅介于-5～5 m之间,且95%置信度水位变幅的平均上限线约为0.146 m。研究结果为决策者提供科学依据。 相似文献
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考虑污染源强随机变化和感潮河流潮周期内动态水文条件对水质的影响,建立了优化污染负荷分配的流域水质管理模型。模型以总的允许排污量最大为目标函数,流域的水质控制点达标为约束条件。假设排污量是服从对数正态分布的随机变量,并且以潮周期内水质达标的概率作为衡量控制点达标的依据。采用遗传算法对该随机规划模型进行求解。研究结果表明,污染负荷优化分配结果能够满足随机条件下的水质达标率要求,并且与传统的确定性线性规划模型的分配结果相比有着明显差别。同时证实了遗传算法能够有效地解决复杂的随机规划模型。 相似文献
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Gradual Deformation and Iterative Calibration of Gaussian-Related Stochastic Models 总被引：11，自引：0，他引：11
Lin Y. Hu 《Mathematical Geology》2000,32(1):87-108
This paper describes a new method for gradually deforming realizations of Gaussian-related stochastic models while preserving their spatial variability. This method consists in building a stochastic process whose state space is the ensemble of the realizations of a spatial stochastic model. In particular, a stochastic process, built by combining independent Gaussian random functions, is proposed to perform the gradual deformation of realizations. Then, the gradual deformation algorithm is coupled with an optimization algorithm to calibrate realizations of stochastic models to nonlinear data. The method is applied to calibrate a continuous and a discrete synthetic permeability fields to well-test pressure data. The examples illustrate the efficiency of the proposed method. Furthermore, we present some extensions of this method (multidimensional gradual deformation, gradual deformation with respect to structural parameters, and local gradual deformation) that are useful in practice. Although the method described in this paper is operational only in the Gaussian framework (e.g., lognormal model, truncated Gaussian model, etc.), the idea of gradually deforming realizations through a stochastic process remains general and therefore promising even for calibrating non-Gaussian models. 相似文献
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Groundwater resource estimates require the calculation of recharge using a daily time step. Within climate-change impact studies, this inevitably necessitates temporal downscaling of global or regional climate model outputs. This paper compares future estimates of potential groundwater recharge calculated using a daily soil-water balance model and climate-change weather time series derived using change factor (deterministic) and weather generator (stochastic) methods for Coltishall, UK. The uncertainty in the results for a given climate-change scenario arising from the choice of downscaling method is greater than the uncertainty due to the emissions scenario within a 30-year time slice. Robust estimates of the impact of climate change on groundwater resources require stochastic modelling of potential recharge, but this has implications for groundwater model runtimes. It is recommended that stochastic modelling of potential recharge is used in vulnerable or sensitive groundwater systems, and that the multiple recharge time series are sampled according to the distribution of contextually important time series variables, e.g. recharge drought severity and persistence (for water resource management) or high recharge years (for groundwater flooding). Such an approach will underpin an improved understanding of climate change impacts on sustainable groundwater resource management based on adaptive management and risk-based frameworks. 相似文献
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The currently adopted rainfall-based design flood estimation method in Australia, known as design event approach (DEA), has a flaw that is widely criticized by the hydrologists. The DEA is based on the assumption that a rainfall depth of a certain frequency can be transformed to a flood peak of the same frequency by adopting the ‘representative values’ of other model input variables, such as temporal patterns and losses. To overcome the limitation associated with the DEA, this paper develops stochastic model inputs to apply Monte Carlo simulation technique (MCST) for design flood estimation. This uses data from 86 pluviograph stations and six catchments from eastern New South Wales (NSW), Australia, to regionalize the distributions of various input variables (e.g., rainfall duration, inter-event duration, intensity and temporal patterns and loss and routing characteristics) to simulate thousands of flood hydrographs using a nonlinear runoff routing model. The regionalized stochastic inputs are then applied with the MCST to two catchments in eastern NSW. The results indicate that the developed MCST provide more accurate flood quantile estimates than the DEA for the two test catchments. The particular advantage of the new MCST and stochastic design input variables is that it reduces the subjectivity in the selection of model input values in flood modeling. The developed MCST can be adapted to other parts of Australia and other countries. 相似文献