共查询到20条相似文献，搜索用时 890 毫秒
1.
A multi-resolution workflow to generate high-resolution models constrained to dynamic data 总被引：2，自引：0，他引：2
Céline Scheidt Jef Caers Yuguang Chen Louis J. Durlofsky 《Computational Geosciences》2011,15(3):545-563
Distance-based stochastic techniques have recently emerged in the context of ensemble modeling, in particular for history
matching, model selection and uncertainty quantification. Starting with an initial ensemble of realizations, a distance between
any two models is defined. This distance is defined such that the objective of the study is incorporated into the geological
modeling process, thereby potentially enhancing the efficacy of the overall workflow. If the intent is to create new models
that are constrained to dynamic data (history matching), the calculation of the distance requires flow simulation for each
model in the initial ensemble. This can be very time consuming, especially for high-resolution models. In this paper, we present
a multi-resolution framework for ensemble modeling. A distance-based procedure is employed, with emphasis on the rapid construction
of multiple models that have improved dynamic data conditioning. Our intent is to construct new high-resolution models constrained
to dynamic data, while performing most of the flow simulations only on upscaled models. An error modeling procedure is introduced
into the distance calculations to account for potential errors in the upscaling. Based on a few fine-scale flow simulations,
the upscaling error is estimated for each model using a clustering technique. We demonstrate the efficiency of the method
on two examples, one where the upscaling error is small, and another where the upscaling error is significant. Results show
that the error modeling procedure can accurately capture the error in upscaling, and can thus reproduce the fine-scale flow
behavior from coarse-scale simulations with sufficient accuracy (in terms of uncertainty predictions). As a consequence, an
ensemble of high-resolution models, which are constrained to dynamic data, can be obtained, but with a minimum of flow simulations
at the fine scale. 相似文献
2.
Tobias Lochbühler Guillaume Pirot Julien Straubhaar Niklas Linde 《Mathematical Geosciences》2014,46(5):625-645
Geophysical tomography captures the spatial distribution of the underlying geophysical property at a relatively high resolution, but the tomographic images tend to be blurred representations of reality and generally fail to reproduce sharp interfaces. Such models may cause significant bias when taken as a basis for predictive flow and transport modeling and are unsuitable for uncertainty assessment. We present a methodology in which tomograms are used to condition multiple-point statistics (MPS) simulations. A large set of geologically reasonable facies realizations and their corresponding synthetically calculated cross-hole radar tomograms are used as a training image. The training image is scanned with a direct sampling algorithm for patterns in the conditioning tomogram, while accounting for the spatially varying resolution of the tomograms. In a post-processing step, only those conditional simulations that predicted the radar traveltimes within the expected data error levels are accepted. The methodology is demonstrated on a two-facies example featuring channels and an aquifer analog of alluvial sedimentary structures with five facies. For both cases, MPS simulations exhibit the sharp interfaces and the geological patterns found in the training image. Compared to unconditioned MPS simulations, the uncertainty in transport predictions is markedly decreased for simulations conditioned to tomograms. As an improvement to other approaches relying on classical smoothness-constrained geophysical tomography, the proposed method allows for: (1) reproduction of sharp interfaces, (2) incorporation of realistic geological constraints and (3) generation of multiple realizations that enables uncertainty assessment. 相似文献
3.
Abderraouf El Ouazzani Taibi Amro Elfeki Guoping Zhang 《Arabian Journal of Geosciences》2011,4(5-6):1005-1018
The research presented in this paper focuses on the application of a newly developed physically based watershed modeling approach, which is called representative elementary watershed approach. The study stressed the effects of uncertainty of input parameters on the watershed responses (i.e., simulated discharges). The approach was applied to the Zwalm catchment, which is an agriculture-dominated watershed with a drainage area of 114 km2 located in East Flanders, Belgium. Uncertainty analysis of the model parameters is limited to the saturated hydraulic conductivity because of its high influence on the watershed hydrologic behavior and availability of the data. The assessment of output uncertainty is performed using the Monte Carlo method. The ensemble statistical watershed responses and their uncertainties are calculated and compared with measurements. The results show that the measured discharges fall within the 95% confidence interval of the modeled discharge. This provides the uncertainty bounds of the discharges that account for the uncertainty in saturated hydraulic conductivity. The methodology can be extended to address other uncertain parameters as far as the probability density function of the parameter is defined. 相似文献
4.
Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization 总被引：2，自引：0，他引：2
This paper proposes a novel history-matching method where reservoir structure is inverted from dynamic fluid flow response.
The proposed workflow consists of searching for models that match production history from a large set of prior structural
model realizations. This prior set represents the reservoir structural uncertainty because of interpretation uncertainty on
seismic sections. To make such a search effective, we introduce a parameter space defined with a “similarity distance” for
accommodating this large set of realizations. The inverse solutions are found using a stochastic search method. Realistic
reservoir examples are presented to prove the applicability of the proposed method. 相似文献
5.
Continuous Facies Updating Using the Ensemble Kalman Filter and the Level Set Method 总被引：1，自引：1，他引：0
We present a methodology based on the ensemble Kalman filter (EnKF) and the level set method for the continuous model updating of geological facies with respect to production data. Geological facies are modeled using an implicit surface representation and conditioned to production data using the ensemble Kalman filter. The methodology is based on Gaussian random fields used to deform the facies boundaries. The Gaussian random fields are used as the model parameter vector to be updated sequentially within the EnKF when new measurements are available. We show the successful application of the methodology to two synthetic reservoir models. 相似文献
6.
为理解地下水位观测信息在非饱和水流数据同化中的数据价值,建立了基于地下水位动态观测信息的一维饱和-非饱和水流集合卡尔曼滤波,通过虚拟数值实验检验了地下水位观测信息在非饱和水力参数估计和水分校正中的潜在价值。研究结果表明:在以地下水位为唯一观测数据时,同时更新参数和水头比仅更新水头能更好地校正土壤剖面的水头分布;当多层单个水力参数未知时,地下水位观测可以为参数估计提供有效信息;当多层多个参数未知时,地下水位与多层多个参数之间的复杂关系导致观测信息难以估计出最优的(唯一的)参数值;地下水位可作为辅助信息,与含水量观测等信息联合运用改善参数估计和含水量预测精度。 相似文献
7.
Geologic uncertainties and limited well data often render recovery forecasting a difficult undertaking in typical appraisal
and early development settings. Recent advances in geologic modeling algorithms permit automation of the model generation
process via macros and geostatistical tools. This allows rapid construction of multiple alternative geologic realizations.
Despite the advances in geologic modeling, computation of the reservoir dynamic response via full-physics reservoir simulation
remains a computationally expensive task. Therefore, only a few of the many probable realizations are simulated in practice.
Experimental design techniques typically focus on a few discrete geologic realizations as they are inherently more suitable
for continuous engineering parameters and can only crudely approximate the impact of geology. A flow-based pattern recognition
algorithm (FPRA) has been developed for quantifying the forecast uncertainty as an alternative. The proposed algorithm relies
on the rapid characterization of the geologic uncertainty space represented by an ensemble of sufficiently diverse static
model realizations. FPRA characterizes the geologic uncertainty space by calculating connectivity distances, which quantify
how different each individual realization is from all others in terms of recovery response. Fast streamline simulations are
employed in evaluating these distances. By applying pattern recognition techniques to connectivity distances, a few representative
realizations are identified within the model ensemble for full-physics simulation. In turn, the recovery factor probability
distribution is derived from these intelligently selected simulation runs. Here, FPRA is tested on an example case where the
objective is to accurately compute the recovery factor statistics as a function of geologic uncertainty in a channelized turbidite
reservoir. Recovery factor cumulative distribution functions computed by FPRA compare well to the one computed via exhaustive
full-physics simulations. 相似文献
8.
Simultaneous Integration of Pressure, Water Cut,1 and 4-D Seismic Data In Geostatistical Reservoir Modeling 总被引：1，自引：0，他引：1
A geostatistically-based inverse technique, the sequential-self calibration (SSC) method, is used to update reservoir models so that they match observed pressure, water cut and time-lapse water saturation derived from 4-D seismic. Within the SSC, a steady-state genetic algorithm (GA) is applied to search the optimal master point locations, as well as the associated optimal permeability perturbations at the master locations. GA provides significant flexibility for SSC to parameterize master point locations, as well as to integrate different types of dynamic data because it does not require sensitivity coefficients. We show that the coupled SSC/GA method is very robust. Integrating dynamic data can significantly improve the characterization of reservoir heterogeneity with reduced uncertainty. Particularly, it can efficiently identify important large-scale spatial variation patterns (e.g., well connectivity, near well averages, high flow channels and low flow barriers) embedded in the reservoir heterogeneity. Using dynamic data, however, could be difficult to reproduce the permeability values on the cell-by-cell basis for the entire model. This reveals the important evidence that dynamic data carry information about large-scale spatial variation features, while they may be not sufficient to resolve the individual local values for the entire model. Through multiple realization analysis, the large-scale spatial features carried by the dynamic data can be extracted and represented by the ensemble mean model. Furthermore, the region informed by the dynamic data can be identified as the area with significant reduced variances in the ensemble variance model. Within this region, the cell-by-cell correlation between the true and updated permeability values can be significantly improved by integrating the dynamic data. 相似文献
9.
地下水反应运移模型具有参数个数众多,观测数据类型多样的特点。为了探究不同类型观测数据在反应运移模拟数据同化中的数据价值,构建了三氯乙烯降解反应运移模型的理想算例,基于水头和浓度两种类型观测数据,采用集合卡尔曼滤波方法推估渗透系数和贮水系数的非均质空间分布,讨论了影响同化结果的因素。结果表明:与仅同化水头数据的结果相比,联合同化水头和浓度观测数据推估渗透系数场和贮水系数场时具有更高的精度,在观测数据拟合和模型预测方面也有更好的表现。与目前溶质运移模型、非饱和流模型等地下水模型中的研究结果相似,数据同化结果受样本数量,观测井的数量和位置的影响,合理优化布置监测井和选择样本数量可有效改善数据同化效果并提高计算效率。 相似文献
10.
Obtaining accurate geological boundaries and assessing the uncertainty in these limits are critical for effective ore resource and reserve estimation. The uncertainty in the extent of an ore body can be the largest source of uncertainty in ore resource estimation when drilling is sparse. These limits are traditionally interpreted deterministically and it can be difficult to quantify uncertainty in the boundary and its impact on ore tonnage. The proposed methodology is to consider stochastic modeling of the ore boundary with a distance function recoding of the available data. This technique is modified to incorporate non-stationarities in the form of a locally varying anisotropy field used in kriging and sequential Gaussian simulation. Implementing locally varying anisotropy kriging retains the geologically realistic features of a deterministic model while allowing for a stochastic assessment of uncertainty. A case study of a gold deposit in Northern Canada is used to demonstrate the methodology. The proposed technique generates realistic, curvilinear geological boundary models and allows for an assessment of the uncertainty in the model. 相似文献
11.
Geological structures can be of great influence groundwater movement and accumulation in the surface and subsurface, and should therefore be taken into consideration in studies related to groundwater contamination impact. This study attempts to investigate the influence of geological structures on groundwater flow and groundwater salinity in Al Jaaw Plain, United Arab Emirates. A set of thematic maps derived from digital elevation model (DEM), LANDSAT, and Spaceborn Imagine Radar-C/X-Band Synthetic Aperture Radar were enhanced by applying Soble filter with 10 % threshold and equalization enhancement to reveal and map geological structures crosscut the entire region. Drainage pattern was derived from DEM automatically using D8 algorithm. The algorithm determines in which neighboring pixel any water in a central pixel will flow naturally. The trends of geological structures and drainage pattern extracted from remote sensing data were correlated with the spatial variation of hydraulic head, thickness aquifer, and groundwater salinity in the region. The results of the study reveal that the wadi courses, thickness of the aquifer, and topography are structural controlled by NNW–SSE, NE–SW, and ENE–WSW trending fault zones, significantly influencing the groundwater flow and groundwater contamination in Al Jaaw Plain. 相似文献
12.
Expanding groundwater datasets collected by automated sensors, and improved groundwater databases, have caused a rapid increase in calibration data available for groundwater modeling projects. Improved methods of subsurface characterization have increased the need for model complexity to represent geological and hydrogeological interpretations. The larger calibration datasets and the need for meaningful predictive uncertainty analysis have both increased the degree of parameterization necessary during model calibration. Due to these competing demands, modern groundwater modeling efforts require a massive degree of parallelization in order to remain computationally tractable. A methodology for the calibration of highly parameterized, computationally expensive models using the Amazon EC2 cloud computing service is presented. The calibration of a regional-scale model of groundwater flow in Alberta, Canada, is provided as an example. The model covers a 30,865-km2 domain and includes 28 hydrostratigraphic units. Aquifer properties were calibrated to more than 1,500 static hydraulic head measurements and 10 years of measurements during industrial groundwater use. Three regionally extensive aquifers were parameterized (with spatially variable hydraulic conductivity fields), as was the aerial recharge boundary condition, leading to 450 adjustable parameters in total. The PEST-based model calibration was parallelized on up to 250 computing nodes located on Amazon’s EC2 servers. 相似文献
13.
In an aquifer, heterogeneity plays an important role in governing groundwater flow. Hence, aquifer characterization should involve both the pattern and values of the hydrogeological parameters. A new analytical solution describing the one-dimensional groundwater flow in a multi-zone unconfined aquifer is presented, and a methodology developed from the analytical solution and a heuristic approach for determining the pattern and values of the aquifer parameters are proposed. The analytical solution demonstrates that the hydraulic head varies spatially and is influenced by aquifer heterogeneity. Simulated annealing, a heuristic approach, is incorporated with the solution to simultaneously identify the pattern and values of the hydraulic conductivity for a horizontal multi-zone unconfined aquifer. This approach may be used to give an approximate result for a two-dimensional problem by dividing the model area into a number of transects along the transverse direction, identifying the parameter values along the longitudinal direction for each transect, and then smoothing the identified results. 相似文献
14.
This study applies an optimal procedure to identify the spatial distribution of groundwater hydraulic conductivity for a confined aquifer in north Taiwan. The parameter structure is determined by the number of zones, zonation pattern, and an uniform hydraulic conductivity associated with each zone. The proposed optimal procedure uses the Voronoi diagram in describing zonation and applies simulated annealing algorithm to optimize its pattern and associated hydraulic conductivity. Three criteria are defined to stop the searching process, including the residual error, the parameter uncertainty, and the structure error. Observation hydraulic heads in years 2000 and 2001 and hydraulic conductivity value from pumping tests are used. The results show that the parameter structure with five zones conforms to the three criteria and, thus, is recommended for future groundwater simulation for the study site. Different heuristic algorithms may also play the role of simulated annealing to optimize the parameter structure. However, which optimization algorithm is more efficient is not discussed and requires further study. 相似文献
15.
基于MODFLOW参数不确定性的地下水水流数值模拟方法 总被引：1，自引：0，他引：1
考虑到模型不确定性引起的地下水数值模拟不确定性对模拟过程的影响,在简要介绍含水层水文地质参数变异性研究进展和地质统计学的基础上,基于常用的确定性地下水流数值模拟软件MODFLOW开发了MODFLOW-Gslib软件,相较于传统的数值模拟方法,将地质统计学与数值模拟结合的方法能够模拟非均质含水层中的参数变异性问题。将MODFLOW-Gslib软件运用于模拟实例中,选择常见的不确定性因素进行模拟,并对其模拟产生的数据进行统计分析,结果表明,软件转化后的参数符合水文地质参数不确定性的相关特征;与原模拟结果进行对比,该软件能够更加真实地刻画含水层参数变异性特征。 相似文献
16.
地下水流数值模型不仅是认识深部水动力场形成演化机制的有效工具,也是建立核素迁移数值模型的基础,因而是高放废物处置场选址和安全评价中重要的技术手段。高放废物深地质处置地下水流数值模拟方法较多,如何选择适当的方法也是值得关注的问题。针对高放废物深地质处置地下水流数值模拟技术展开研究,通过阅读大量国内外文献,文章系统阐述了目前常用的4 类地下水流数值模拟方法的研究进展、适用条件和实例应用;综述了深地质处置中常用的模型不确定性分析方法及研究成果,列表给出了适用于放射性废物地质处置的地下水流数值模拟软件及其在废物处置选择和安全评价中的应用。研究结果表明:等效连续介质模型适用于大区域、长序列、裂隙发育程度较高或较均匀的地区,该类模型方法成熟、所需的数据和参数易于获得,但是不能精确刻画裂隙介质中地下水的流动特征。离散裂隙网络模型适合解决处置场地、储罐尺度等需要精细刻画的地下水流问题,但由于需要大量裂隙及其连通性数据、相关参数等,该方法存在着工作量大、耗时多的缺点。双重介质模型主要用于解决区域尺度裂隙水流问题,但并不能表现出裂隙介质的各向异性、不连续性等特征,因而适用范围存在一定的限制。等效-离散耦合模型可以通过区域分解法对裂隙密度大的区域采用等效连续介质模型,对于裂隙密度较小的地区采用离散裂隙网络模型,从而更符合一般地质条件下裂隙渗流的特征,但也存在交换量难以确定、模型耦合技术问题。通过灵敏度分析,将不同敏感因子对模型敏感指标的影响程度进行排序,提高模型精度、减少参数不确定性分析的工作量。蒙特卡罗法是目前常用的一种模型不确定性方法,原理简单、易于实现。文章展望了数值模型在仿真性、不确定性分析、预测和多介质耦合等方面的研究前景。 相似文献
17.
In this paper, an experimental methodology is presented using digital image techniques to assess the internal microcracks and to quantify the rock damage within rock cores. The second part of the work is devoted to the numerical estimation of the tensile blast induced damage evolution law. The set up methodology is then applied to a set of limestone cores which were sampled before and after a real field blast round. The image analysis algorithm which was developed during the present work is based on a segmentation technique that uses a particular thresholding. Petrographic parameters, such as crack number, orientation, extension, centroid position were computed as a first step aiming at a fine characterization of the cracked medium. The most important estimated parameter is the specific crack area which is defined as the ratio between the crack area and the total image area. This parameter was taken as the rock internal damage. A dynamic tensile damage ordinary partial differential equation is numerically solved and calibrated with the obtained data in order to derive a general blast induced damage evaluation law within the muckpile blocks. The application of the numerical algorithm to cores coming from sampled blocks before and after real field blasts allowed the estimation of damage parameter and dynamic stress evolution histories as well as an estimation of the microfracturing activation and growth energies used during the blast. 相似文献
18.
地铁深基坑支护的遗传神经网络位移反分析 总被引：2，自引：0，他引：2
针对目前已有的各种位移反分析方法存在的缺陷,利用神经网络具有的非线性映射能力和遗传算法具有的全局随机搜索能力,提出了一种基于遗传神经网络进行深基坑支护的位移反分析方法。该方法改变了BP算法依赖梯度信息的指导来调整网络权值的方法,而是利用遗传算法全局性搜索的特点,寻找最合适的网络连接权和网络结构等来达到优化的目的。结合地铁深基坑支护位移计算,应用该方法对某一地铁深基坑土体的力学参数进行了反演。结果表明：将位移观测值作为网络输入数据,土体力学参数作为输出数据,在较大的解空间内,该位移反分析方法收敛速度快、解的稳定性好、反演结果精度高,是一种理想的位移反分析方法。最后,采用该软件结合一个工程实例实现了应用遗传神经网络进行的基坑支护位移反分析。 相似文献
19.
20.
在冲积含水层中,由于岩相的非均质分布,渗透系数一般呈现出明显的非高斯特性（例如砂和黏土两种岩相）,非高斯特性给地下水模型参数的推估带来了困难与挑战。目前广泛使用的集合平滑数据同化方法（ESMDA）虽然有效且计算成本较低,但仅适用于高斯场。多点地质统计方法虽已广泛用于模拟非高斯场,但其无法融入动态观测数据推估参数。基于多点地质统计方法中的直接采样法（DS）与集合平滑数据同化方法,构建一种新的数据同化框架（ESMDA-DS）,既可保持参数场的非高斯特性,又可融合多源数据精确推估非高斯场。构建三个理想算例验证ESMDA-DS对非高斯参数场的推估效果,并探讨了不同类型观测数据对推估效果、水位与浓度预测精度的影响。三个理想算例包括仅融合水位数据（Case 1）,同时融合水位与浓度数据（Case 2）,同时融合水位、浓度与对数渗透系数数据（Case 3）。结果表明:ESMDA-DS方法结合了ESMDA与DS的各自优势,能有效融合观测数据推估渗透系数场,并保持参数场的非高斯特性。通过对比三个算例推估结果,Case 3的参数场推估效果最好,水位与浓度预测精度最高,Case 2次之,Case 1最差,表明融合多源数据可改善推估效果,提高预测精度。 相似文献