基于改进K-SVD字典学习方法的地震数据去噪

为实现更好的地震数据去噪技术,笔者引入一种新的算法:快速迭代收缩阀值法(FISTA),通过FISTA和K-奇异值分解(K-SVD)不断迭代更新K-SVD字典,利用更新得到的K-SVD字典对地震数据进行稀疏表示,去除稀疏系数中较小的数值,使数据中的随机噪声得到压制。对层状模型合成地震记录,Marmousi模型合成地震记录以及实际地震数据进行对比实验,得出FISTA算法较OMP算法能更好地提高地震数据的信噪比,同时有效地保护了反射信号。     

形态分量分析在去除地震资料随机噪声中的应用

以数学形态学和稀疏信号理论为依据,采用形态分量分析(MCA)方法去除地震数据中的随机噪声。应用MCA方法的关键在于选取合适的字典,从地震数据的特点和计算复杂性出发,选取UWT字典和Curvelet字典,一个用来稀疏表示地震数据的局部奇异部分,一个用来稀疏表示地震数据的线状变化部分。采用BCR算法求解目标函数,通过将数据分解为形态特征不同的2个分量,舍弃在字典中不能有效稀疏表示的随机噪声来达到去噪目的。作为一种二维去噪方法,MCA去噪方法在时间和空间方向上都具有很强的随机噪声抑制能力;由于UWT字典和Curvelet字典能够比传统的小波变换有更强的稀疏表示能力,MCA去噪方法对有效信息的损害较小,是一种保真保幅的去噪方法。模型测试和实际资料处理验证了该方法的有效性。     

野外数据采集系统数据字典的研制

数据字典在整个信息系统生命周期里都起着重要的作用,以野 集系统为例,了数据字典研制的基本方法,详细分析了表属性字典,字段属性字典,表格字段字典,索引信息字典,数据均束字典以及存储各表格关系的关键系典等多种字典的数据结构特征。     

局部时频变换域地震波吸收衰减补偿方法

地震信号在地下传播时会受到地层吸收衰减的影响,从而降低了地震资料的分辨率。因此地震波吸收衰减补偿是地震资料处理中的一项重要环节。本文研究的地层吸收衰减补偿方法主要基于局部时频变换(LTFT),该方法能够调节选取谱分解的频率范围和频率采样间隔,解决了短时傅里叶变换固定时窗和小波系数无法提供波形频率的精确估计值问题,适用于非平稳地震信号的时频分析。在求取地层Q值的方法中,频谱比值法具有高效简单的特点,有着广泛的应用范围。本文假设地下介质为层状变Q模型,使用局部时频变换将信号转换为时频域,通过频谱比值法求出各层的Q值,最后根据Kolsky衰减模型来补偿地震信号。理论模型测试和实际资料处理的结果表明,本文提出的方法能够有效恢复衰减信号,提高地震资料的分辨率。     

基于LDPC矩阵采样方法的三维地震数据重构

按照以往的测量矩阵进行实际勘察无法较好地实现地震数据的重构,大多数矩阵设计复杂且元素多样,不符合实际标准。笔者将LDPC矩阵应用到地震勘探采样中,用较少的地震数据来重构完整的地震记录。采用K-SVD字典对数据进行稀疏变换,FISTA算法进行重构。对比以往的随机采样、离散均匀采样和jitter采样,LDPC矩阵更适合三维环境且恢复重构效果更好。对比重构数据的信噪比,三维模拟数据和实际数据都证实了LDPC矩阵信噪比值最高,重构出的数据效果最好。     

PRB数字地质填图前期数据准备及PRB过程字典库建立

PRB数字地质填图前期数据准备包括软硬件准备、地形图数值化、前人资料的收集和室内录入、多元数据的叠加和整合、PRB过程字典库的编制等方面.PRB过程字典库由结构化字典、填缺式字典和描述性字典3部分组成.结构化字典和填缺式字典可直接查询, 为1~1.5级字典, 描述性字典为2级字典, 需要2级查询.不同的字典类型均以文本文档的形式存在, 文件名后缀为.DIC.      

Prior model identification during subsurface flow data integration with adaptive sparse representation techniques

Construction of predictive reservoir models invariably involves interpretation and interpolation between limited available data and adoption of imperfect modeling assumptions that introduce significant subjectivity and uncertainty into the modeling process. In particular, uncertainty in the geologic continuity model can significantly degrade the quality of fluid displacement patterns and predictive modeling outcomes. Here, we address a standing challenge in flow model calibration under uncertainty in geologic continuity by developing an adaptive sparse representation formulation for prior model identification (PMI) during model calibration. We develop a flow-data-driven sparsity-promoting inversion to discriminate against distinct prior geologic continuity models (e.g., variograms). Realizations of reservoir properties from each geologic continuity model are used to generate sparse geologic dictionaries that compactly represent models from each respective prior. For inversion initially the same number of elements from each prior dictionary is used to construct a diverse geologic dictionary that reflects a wide range of variability and uncertainty in the prior continuity. The inversion is formulated as a sparse reconstruction problem that inverts the flow data to identify and linearly combine the relevant elements from the large and diverse set of geologic dictionary elements to reconstruct the solution. We develop an adaptive sparse reconstruction algorithm in which, at every iteration, the contribution of each dictionary to the solution is monitored to replace irrelevant (insignificant) elements with more geologically relevant (significant) elements to improve the solution quality. Several numerical examples are used to illustrate the effectiveness of the proposed approach for identification of geologic continuity in practical model calibration problems where the uncertainty in the prior geologic continuity model can lead to biased inversion results and prediction.     

数据字典在地质矿产术语分类代码修编平台中的应用

基于B/S模式的《地质矿产术语分类代码》（GB 9649-1988）修编平台是提高该标准修编工作效率的一种必然手段,而数据字典在该平台中的穿插使用保证了修编工作的合理与安全.通过论述数据字典技术在实现修编平台的修编权限控制、修编版本管理功能中的具体应用,体现了数据字典技术在数据处理方面的独特优势.数据字典技术在该平台中的应用,不仅对修编人员的修编权限进行了灵活的约束,而且修编过程中产生的不同版本也得到了有效的管理.     

小波变换与地震奇异性属性

地震属性是由地震数据提取的有关地震波的几何形态、运动学特征、动力学特征和统计学特征等组成。这里主要讨论了一种新的地震属性(奇异性属性)计算方法。由于地震数据携带着大量的奇异性信息,因此,这一新的地震属性是在偏移地震数据的小波变换和奇异性分析的基础上形成的。小波变换使检测数据中的局部奇异程度成为可能。为能够估计出偏移地震数据每一采样点的局部奇异规律,从小波变换系数的角度来提取地震信号的奇异指数。这种新属性实行单道处理,不需要子波和速度信息,它给出了地下分层情况和断层位置。在地震数据奇异性属性的基础上,用小波变换来划分地层旋回,从而提高了小波变换在地震解释中的应用。     

Random seismic noise attenuation data using the discrete and the continuous wavelet transforms

In this paper, we propose a technique of random noise attenuation from seismic data using discrete and continuous wavelet transforms. Firstly, the discrete wavelet transform (DWT) is applied to denoise seismic data using the threshold method. After, we calculate the continuous wavelet transform of the denoised seismic seismogram, the final denoised seismic seismogram is the continuous wavelet transform coefficients at the lower scale. Application to a synthetic seismogram shows the robustness of the proposed tool for random noise attenuation. Application to real vertical seismic profile recorded in Algeria clearly shows the efficiency of the proposed tool for random noise attenuation.     

The initiation of pull‐apart basins and transform continental margins: results from numerical experiments of kinematic partitioning in divergent settings

We present a set of numerical models to investigate how transform faults initiate in pull‐apart basins or transform continental margins. The model represents an elastic plate with three aligned weak spots. Applying strain on the edge of the model firstly propagates extensional cracks from the pre‐existing damaged spots. The subsequent evolution depends on the angle (obliquity) between the applied strain and the alignment of the damaged spots. For obliquity <50°, transform faults form to connect en‐échelon divergent cracks; for obliquity >60°, transtensional transfer zones connect the divergent cracks and no transform fault forms. These experiments suggest that pull‐apart basins do not form as previously assumed by connection of overlapping transform faults, but that transform faults form as connections of extensional areas.     

Attenuation of multiple waves using the continuous wavelet transform (CWT)

This paper describes how the continuous wavelet transform is used to filter multiple waveforms in both time and frequency domains. It is well suited to process the stationary signals, and it shows the signal in both time and frequency scales. This new approach was tested first on synthetic data and then on real data. The results obtained on both cases were good. The method consists of identifying the multiples on which we apply a normal move out using the multiple velocity law. The multiples will be aligned and the primary reflections will not be aligned. This operation allows locating the multiples in the time-scale domain. We compute the continuous wavelet transform (CWT for short) in order to focus on the patterns relative to seismic events. To filter the multiples, we define a zone with frequency and time bounds. These bounds are deduced from the projection of the seismic trace. Then an automatic mask is applied to the pattern to be isolated. Filtering in time–frequency domain is done by keeping only the wavelet coefficients that are outside the mask and assigning zero to the coefficients larger than a threshold amplitude inside the defined zone. The mask shape does not matter, which is not the case in classical filtering, where both the window size and shape play a key role. The mask is defined from three parameters: time, frequency, and the wavelet coefficients. To go back to the time domain, one has to compute the wavelet transform inverse of the trace. This procedure is repeated for all traces. To reset the traces to their initial positions, we apply the dynamic correction inverse with the same velocity law as the multiples. It turns out that the attenuation of multiples by the CWT works fine, in particular, the two identified multiples were quasi eliminated (Fig. 10).     

数据字典在煤炭数据发布平台中的应用

介绍了数据字典技术在基于网络B/S结构的“全国煤炭资源网络信息系统”——煤炭数据发布平台中的应用情况。系统通过数据字典技术进行用户访问控制、数据语义规格化和显示页面动态定制等工作。数据字典技术在该系统中的应用, 不仅使系统管理人员能够统一、高效、灵活地进行访问控制, 而且能根据需求定制显示内容, 保证了系统的安全性和功能的完善性。      

Wavelet Transforms Applied to Irregularly Sampled Soil Data

Wavelet transforms have been used widely to analyse environmental data. These data typically comprise a series of measurements taken at regular intervals in time or space. The analysis offers a decomposition of the data that distinguishes components at different spatial scales but also, unlike Fourier analysis, can resolve local intermittent features. Most wavelet methods require the data to be sampled at regular intervals and little attention has been paid to developing methods for data that are not. In this paper, we derive a discrete Haar wavelet transform for irregularly sampled data and show how the resulting wavelet coefficients can be used to estimate contributions of variance. We discuss the interpretation of these statistics using data on apparent soil electrical conductivity of soil measured across a landscape as an example.     

Spectral-type simulation of spatially correlated fracture set properties

Fracture set properties such as orientation, spacing, trace length, and waviness tend to be spatially correlated. These properties can be efficiently simulated by spectral analysis procedures that take advantage of the computational speed of the fast Fourier transform. The covariance function of each property to be simulated is obtained from the variogram function estimated from mapped fracture set data and is typically referenced to the mean vector of the set. Simulation procedures for normally and exponentially distributed data involve generating uncorrelated Fourier coefficients that are assigned proper variance according to the spectral density, which is the Fourier transform of the covariance function. These coefficients are then reverse Fourier transformed to produce simulated set properties that have the desired variance and variogram function.     

基于测井数据小波变换的层序划分

探讨了小波变换用于测井层序划分的一种方法。在论述了小波变换对信号时频分析的优势后, 介绍了连续小波变换的定义和一般步骤。以鲁西某钻井为例, 对迄今为止所能获得的分辨率最高、连续性最好的测井地质数据, 进行了连续小波变换, 提取小波变换系数的时频色谱信息。在此基础之上, 将不同时间 (深度) 尺度的旋回清晰地展现出来, 并探测到地层序列中不同级别的突变点, 从而实现对鲁西地区石炭二叠系层序、准层序的划分。这些探索为地层层序的划分提供了一种新的思路和有效途径。      

Two-dimensional Conditional Simulations Based on the Wavelet Decomposition of Training Images

Scale dependency is a critical topic when modeling spatial phenomena of complex geological patterns that interact at different spatial scales. A two-dimensional conditional simulation based on wavelet decomposition is proposed for simulating geological patterns at different scales. The method utilizes the wavelet transform of a training image to decompose it into wavelet coefficients at different scales, and then quantifies their spatial dependence. Joint simulation of the wavelet coefficients is used together with available hard and or soft conditioning data. The conditionally co-simulated wavelet coefficients are back-transformed generating a realization of the attribute under study. Realizations generated using the proposed method reproduce the conditioning data, the wavelet coefficients and their spatial dependence. Two examples using geological images as training images elucidate the different aspects of the method, including hard and soft conditioning, the ability to reproduce some non-linear features and scale dependencies of the training images.     

基于控制字典的对象式地质属性数据管理

传统地质数据管理与应用是参照数据库的外模式来设计数据结构和数据访问接口,在业务逻辑没有发生大的变动情况下,外模式发生更改后,需要修改应用程序才能适应新的数据库结构.鉴于此弊,在关系数据库视图机制的启发下,通过分析不同地质专业地质属性数据的特征,对地质数据库外模式的高度概括,形成用于地质业务分析评价所需的关键属性组成的元组集——控制字典表,基于控制字典抽象出面向地质行业的对象式数据模型、映射数据模型与地质数据的关系,并参照控制字典表的“数据结构”来设计数据访问接口,最终实现地质数据库的动态扩展,无需再修改应用程序,需要做的仅仅是修改控制字典与外模式之间的映射关系,以不变应万变.控制字典作为一个中间件,将用户对地质数据的操作和计算机对地质数据的处理分离开来,充分保证了程序和数据层的逻辑独立性.      

含倾斜定向排列裂隙介质纵波特征

根据Schoenberg的含裂隙介质的线性滑移模型在弱各向异性近似条件下根据Bond变换获得了含倾斜定向排列裂隙介质的弹性系数矩阵。在将含倾斜定向排列裂隙介质视为倾斜横向各项同性（TTI）介质的基础上根据弱各向异性近似条件下TTI介质纵波相速度、弹性波阻抗以及反射系数的近似解析解,研究了裂隙倾斜角对含倾斜定向排列裂隙介质中纵波相速度、反射系数以及波阻抗的影响。研究发现含倾斜裂隙介质的纵波相速度、各向异性弹性波阻抗、反射系数三个参数具有类似方位各向异性特征：入射角大的时候,显示较强方位各向异性,但是这三个参数对入射角的依赖程度却不完全相同,反射系数对入射角的依赖程度最大。     

Glacier‐fed lakes as palaeoenvironmental archives

Glaciers show a sensitive and rapid response to climate shifts. Associated changes in ice extent drive variations in the production of rock flour, the suspended product of glacial erosion. These glacigenic sediments may accumulate in downstream lakes, continuously recording glacier history. Consequently, the lacustrine sediment records of such glacier‐fed lakes represent valuable palaeoenvironmental archives that help constrain past climate variability. In this paper, we discuss the multi‐disciplinary methodological toolbox that is applied to fingerprint a glacier signal from such lake sediments. Special emphasis is placed on dating methods, which transform stratigraphical data into climate time series, allowing us to distinguish leads and lags between archives. We also elaborate on techniques that are used to validate sediment‐based glacier signals and resolve their climate signature. Finally, we conclude with a brief outlook on new research avenues such as proxy data–climate model comparisons.