陆面数据同化系统误差问题研究综述

同化系统中的误差问题一直被认为是制约数据同化性能的瓶颈问题。从分析陆面数据同化系统的误差问题研究现状出发,统一定义了同化系统的误差来源及误差表现,简要综述了顺序同化方法及连续同化方法中的误差定义和相关理论问题。从误差估计的角度,重点介绍了目前研究中各种误差估计的方法和面临的困难。针对误差处理方法的研究,介绍了在集合数据...     

Geophysical properties of zinc‐bearing deposits

At present, most, if not all zinc is being produced from the mineral sphalerite. With the exception of its piezoelectricity and in some cases its density, sphalerite has no salient physical properties to routinely allow its direct detection by geophysical methods. Although the mineral usually occurs with other sulfides, which do respond to various geophysical techniques, detection of zinc‐bearing deposits is often difficult. In this paper, physical property measurements from numerous, mainly Australian, deposits are presented, together with examples from various geophysical surveys. The results are used to suggest the most effective geophysical technique for the direct detection of the different types of zinc‐bearing deposits. Induced polarisation is probably the most effective technique for unmetamorphosed sediment‐hosted deposits and for carbonate‐hosted deposits, whereas electromagnetics is usually the most appropriate method to use for volcanic‐hosted deposits and for sediment‐hosted deposits that have been strongly metamorphosed. Magnetics is the best technique for skarn and ‘Cobar‐style’ deposits. However, it must be emphasised that usually more than one geophysical technique is required before a prospect can be considered to have been thoroughly explored.     

湖南石门雄黄矿床找矿远景探析

在研究成矿条件、成矿规律的基础上 ,用秩相关分析和找矿信息量法对湖南石门雄黄矿床进行预测 ,两种方法相互结合 ,综合遥感、物化探资料及具体的地质情况 ,圈定了 3个Ⅰ级远景区、4个Ⅱ级远景区及 1个Ⅲ级远景区 ,为今后矿山生产探矿及地质队普查找矿提供了依据     

综合物化探方法在地质找矿“攻深找盲”中的应用

物化探找矿方法面临着新形势下复杂地质条件中找矿的新挑战,单一物化探分析方法很难具有说服力,综合各种地质信息和勘探方法显得尤为重要。笔者结合河南省某矿床的找矿实践,介绍了高精度磁测、X荧光土壤分析和EH4测深等物化探综合分析方法,在工作区内发现了与成矿有关的物化探异常,经查证与地表地质现象吻合较好,说明该综合物化探评价技术方法在该矿床的应用是成功的,显示了其快速、高效和精准的特点。     

激电中梯测量在晴隆丁头山铅锌矿找矿中的应用

丁头山是一个老铅锌矿区,2014年贵州省普安罐子窑—水城花嘎铅锌矿整装勘查工作中,在物探方法试验的基础上,选用激电中梯剖面测量开展面积性测量工作。在圈定物探异常的基础上,对重点异常进行了激电测深和不同极距的电阻率联合剖面测量,在丁头山找矿靶区内,根据物探解译成果布置钻孔进行工程验证,在深部发现新的铅锌矿体,新增了铅锌资源量,取得明显的找矿效果。为研究物探手段在老矿区找矿工作中的应用方法及效果,结合前期工作成果,对如何运用物探方法在铅锌区域成矿带中寻找构造控制铅锌矿体进行了初步的探索,对老矿山增储具有一定指导作用。     

Computing derivative information of sequentially coupled subsurface models

A generic framework for the computation of derivative information required for gradient-based optimization using sequentially coupled subsurface simulation models is presented. The proposed approach allows for the computation of any derivative information with no modification of the mathematical framework. It only requires the forward model Jacobians and the objective function to be appropriately defined. The flexibility of the framework is demonstrated by its application in different reservoir management studies. The performance of the gradient computation strategy is demonstrated in a synthetic water-flooding model, where the forward model is constructed based on a sequentially coupled flow-transport system. The methodology is illustrated for a synthetic model, with different types of applications of data assimilation and life-cycle optimization. Results are compared with the classical fully coupled (FIM) forward simulation. Based on the presented numerical examples, it is demonstrated how, without any modifications of the basic framework, the solution of gradient-based optimization models can be obtained for any given set of coupled equations. The sequential derivative computation methods deliver similar results compared to FIM methods, while being computationally more efficient.     

Time variations in the geophysical fields above a gas field on Sakhalin Island

Results of repeated geophysical observations above the Yuzhno-Lugovskoye gas field (southern Sakhalin) carried out from 2003 to 2006 are considered. It is shown that the gas field is a natural indicator of geodynamic processes occurring in the gas field and beyond it. A complex of methods and observations is offered to estimate the degree of productivity of the objects involved in prospecting drilling. They provide further development of the short-term forecast of seismic events by geophysical methods, because seismic pulses propagating from an external source cause sharp changes of the geophysical fields above the gas-containing structure.     

营城煤矿采空区及塌陷区的地球物理特征

采用地球物理方法进行探查采空区(塌陷区)的地球物理特征具有一定的优势。讨论了在营城煤矿未知采空区及塌陷区运用多种地球物理方法测量的结果,得到该煤矿采空区及塌陷区的地球物理特征,从而为营城矿煤采空区及塌陷区的探查与判断提供参考。     

Detection of the near surface structure through a multidisciplinary geophysical approach

The present survey aimed to image the subsurface structure, including karstic voids, and to evaluate the extent of the heterogeneities that can result in potentially dangerous collapse of road segments overlying these features. A multidisciplinary geophysical approach (seismic refraction, frequency domain electromagnetic and ground penetrating radar) in combination with a detailed geological survey indicated the presence of tectonic faults as well as velocity and conductivity anomalies along an old road within the area of Akrotiri at Chania (Crete). Due to the presence of subsurface fuel pipes, perpendicular to the direction of the road, 2D resistivity imaging was excluded from the applied geophysical methods. Interpretation of the geophysical data revealed that the section of the road investigated overlies prominent voids attributed mostly to karst features. The conductivity and velocity anomalies are interpreted to indicate an area where the host limestone rock has been downthrown by faulting and associated karstification. The continuation of this fault zone was observed in the slope of the road during later excavations. Interpretation, using geographic information systems (GIS) to integrate data, allowed these controls and relationships to be understood and monitored. The above methodology was proved successful for areas where the application of resistivity method is not possible.     

A Methodology for Establishing a Data Reliability Measure for Value of Spatial Information Problems

We propose a value of information (VOI) methodology for spatial Earth problems. VOI is a tool to determine whether purchasing a new information source would improve a decision-makers’ chances of taking the optimal action. A prior uncertainty assessment of key geologic parameters and a reliability of the data to resolve them are necessary to make a VOI assessment. Both of these elements are challenging to obtain, as this assessment is made before the information is acquired. We present a flexible prior geologic uncertainty modeling scheme that allows for the inclusion of many types of spatial parameter. Next, we describe how to obtain a physics-based reliability measure by simulating the geophysical measurement on the generated prior models and interpreting the simulated data. Repeating this simulation and interpretation for all datasets, a frequency table can be obtained that describes how many times a correct or false interpretation was made by comparing them to their respective original model. This frequency table is the reliability measure and allows a more realistic VOI calculation. An example VOI calculation is demonstrated for a spatial decision related to aquifer recharge where two geophysical techniques are considered for their ability to resolve channel orientations. As necessitated by spatial problems, this methodology preserves the structure, influence and dependence of spatial variables through the prior geological modeling and the explicit geophysical simulation and interpretations.     

闽南铀矿勘查的物化探方法系列

本文介绍了如何根据闽南地区特定的地质环境、地貌特征,因地制宜地选择物化探方法系列。认为不同找矿阶段、不同地区应选择不同的物化探方法,才能获得较好的地质效果。     

A parallel ensemble-based framework for reservoir history matching and uncertainty characterization

We present a parallel framework for history matching and uncertainty characterization based on the Kalman filter update equation for the application of reservoir simulation. The main advantages of ensemble-based data assimilation methods are that they can handle large-scale numerical models with a high degree of nonlinearity and large amount of data, making them perfectly suited for coupling with a reservoir simulator. However, the sequential implementation is computationally expensive as the methods require relatively high number of reservoir simulation runs. Therefore, the main focus of this work is to develop a parallel data assimilation framework with minimum changes into the reservoir simulator source code. In this framework, multiple concurrent realizations are computed on several partitions of a parallel machine. These realizations are further subdivided among different processors, and communication is performed at data assimilation times. Although this parallel framework is general and can be used for different ensemble techniques, we discuss the methodology and compare results of two algorithms, the ensemble Kalman filter (EnKF) and the ensemble smoother (ES). Computational results show that the absolute runtime is greatly reduced using a parallel implementation versus a serial one. In particular, a parallel efficiency of about 35 % is obtained for the EnKF, and an efficiency of more than 50 % is obtained for the ES.     

A case history of regional geoscience data integration and analysis for the purpose of mineral resource appraisal, kasmere lake area, Manitoba

The methods used to generate a unified cell structured data base for geological, mineral occurrence, geochemical, and three different types of geophysical data are reviewed. The extremes of both excess and paucity of data were encountered and procedures for data compression and interpolation between known values were required. In the latter case a weighted moving average was used to take advantage of knowledge of the regional geological structure in an informal kriging. Classical approaches based on training data sets were investigated and found to be wanting in the area due to the inadequate mineral occurrence data base. The few data cells containing mineral occurrences were known with certainty; however, many of the cells classified as non-mineral occurrence containing, due to the immature exploration history, probably contained mineral occurrences of equal or greater significance. This inadequacy in the mineral occurrence data base confounded formal statistical analysis. An empirical scoring approach was developed which draws on general exploration criteria. This methodology, based on the geochemical and geophysical data, was used to prepare an Athabasca type uranium deposit favorability index. The favorable areas are examined in terms of the known geology. Results show that the majority fell in areas that would also be considered favorable by geologic models for Athabasca type uranium deposits. This empirical approach, based on geochemical and geophysical interpretive procedures, may have particular potential in poorly explored areas lacking good training sets.Paper presented at the 10th Geochautauqua: Computer Applications in the Earth Sciences, 23–24 October 1981, Ottawa, Canada.     

论地球物理方法在寻找金刚石原生矿中的作用

简述了寻找金刚石原生矿的新进展,重点说明了地球物理方法在寻找金伯利岩中的作用,强调了加强基础理论研究和利用综合信息找矿的重要性。     

塔里木盆地非背斜圈闭的勘探方法

根据塔里木盆地可能存在的非背斜圈闭的类型和地质特点,提出了勘探非背斜圈闭油气藏应采取的步骤和方法,以及依据异常高点验证圈闭的新思路。对其勘探的四个步骤和野外地震数据采集、常规精细处理、ＡＶＯ技术、反演技术、目标化解释技术、非背斜圈闭的表征及非背斜圈闭的评价方法等作了具体论述。寻找非背斜圈闭油气藏在于地震运动学与动力学信息的充分应用,在于地震资料的特殊处理和各种新技术的广泛应用。     

河道洪水实时概率预报模型与应用

通过数据同化方法合理地将实时水文观测数据融入到洪水预报模型中,可提高洪水预报模型的实时性和精确度。选取沿程断面流量、水位和糙率系数作为代表水流状态的基本粒子,以监测断面实测水位数据作为观测信息,建立了基于粒子滤波数据同化算法的河道洪水实时概率预报模型。模型应用于黄河中下游河道洪水预报计算的结果表明,采用粒子滤波方法同化观测水位后,不仅可以直接校正水位,同时也可以有效地校正流量和糙率,为未来时刻模型预报计算提供更准确的水流初始条件和糙率取值区间,进而有效地提高模型预报结果的精度,给出合理的概率预报区间。不同预报期的预报结果表明,随着预报期的增长,同化效果减弱,模型预报结果的精度会有所降低,水位概率预报结果受粒子间糙率不同的影响不确定性增加,而流量概率预报结果受给定模型边界条件的影响不确定性降低。所提出模型可以有效同化真实水位观测数据,适合应用于实际的洪水预报工作中。     

Mapping Disastrous Natural Hazards Using Global Datasets

The increased interest for categorising countries at risk calls for an improved methodology allowing comparison of natural hazard impacts at a global level. A disaster is the intersection between a hazardous event, the elements at risk (population, infrastructures) and their vulnerability. In order to associate reported impacts with affected elements and socio-economic or geophysical contextual parameters, geographical location and extent of hazards is needed. The scope of this paper is to present improved automated procedures for a rapid mapping of large disastrous hazard events (floods, earthquakes, cyclones and volcanoes) using Geographical Information Systems (GIS) and available global datasets. Up to 82% of the events and 88% of the reported victims could be geo-referenced and the results highlight both the potentialities and limitations of the methods applied.     

An enhanced ensemble Kalman filter scheme incorporating model error in sequential coupling between flow and geomechanics

In this work, we construct a new methodology for enhancing the predictive accuracy of sequential methods for coupling flow and geomechanics while preserving low computational cost. The new computational approach is developed within the framework of the fixed-stress split algorithm procedure in conjunction with data assimilation based on the ensemble Kalman filter (EnKF). In this context, we identify the high-fidelity model with the two-way formulation where additional source term appears in the flow equation containing the time derivative of total mean stress. The iterative scheme is then interlaced with data assimilation steps, which also incorporate the modeling error inherent to the EnKF framework. Such a procedure gives rise to an “enhanced one-way formulation,” exhibiting substantial improvement in accuracy compared with the classical one-way method. The governing equations are discretized by mixed finite elements, and numerical simulation of a 2D slab problem between injection and production wells illustrate the tremendous achievement of the method proposed herein.     

Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania)

Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N ?? S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands.     

利用正演模拟实现面波衰减

瑞雷波是分布在自由表面附近的P-SV面波,具有强振幅、低频、频散的特征,常用于工程物探,而在油气勘探及深部探测中常作为一种"干扰"波,会影响地震资料的信噪比,需要将面波净化处理。为实现面波衰减,本文将工程物探方法和石油物探技术相结合,通过面波频散曲线反演获得高精度的近地表模型,在三维近地表横波速度模型基础上进行面波正演,利用面波模型自适应匹配相减的方法将其减去,在不伤及有效波的情况下将面波的影响降至最低,一定程度上避免了常规面波衰减方法伤及有效波、损失低频弱信息、导致资料有效频带变窄、对地震构造解释及反演造成负面影响等缺点。最后应用实际数据验证了本研究方法的有效性。