Mean Traveltime Curves Analysis: A Method to Improve Understanding of Data Behaviour in 2-D Transmission Tomography at the Pre-Inversion Stage

Transmission tomography methods show a great sensibility to data variability, which eventually includes data errors, often present in field experiments. Local optimization methods, traditionally used to solve this inverse problem, are very sensitive to these difficulties, failing to converge properly in the presence of spurious data. Regularization methods partially cope with these weaknesses, damping the instabilities.A complementary approach, adopted here, is to perform a structured analysis of data variability before the inversion, oriented to discriminate the contribution of errors from that of true geological heterogeneities. The key concept of mean traveltime curves ( and ) is introduced and described. Their analytical equations are deduced for isotropic homogeneous media and any recording geometry. Empirical mean traveltime curves can be inferred based solely on traveltime data, using the corresponding discrete estimators. The methodology proposed here proceeds through a user-defined subdivision of the domain of interest into isotropic homogeneous areas. Least squares velocity estimations and associated data misfits are used to scrutinize the behaviour of the implied source-receiver sets and of the ray-swept part of the geologic medium. Data are considered suspicious if zonal estimated velocities are non-consistent with a priori information. Also, independent fitting of both empirical curves helps to classify the genesis of the residuals: some situations are illustrated.Finally, we show the application of this technique to a data set from the Grimsel test site in Switzerland. Using this methodology, we detect some anomalous gathers, which may be responsible for the large range of velocities found in the initial imaging with this data set. Also, we give some indications of the possible sources of these anomalies. This approach offers a quick data variability analysis in the pre-processing stage, which, even if no data editing algorithms are finally used, always improves the understanding of the data structure.     

地震波速层析成像方法研究进展

本文回顾了利用天然地震观测获取地下速度结构的方法。尽管有不同的新方法涌现,天然地震波速层析成像方法,尤其是多震相联合反演的格点层析成像方法,是当今使用广泛使用的层析成像方法之一,是对地球内部成像的最有效方式。波速层析成像方法的未来发展首先是提高第一手的观测资料,即增加接收地震波信息的地震台站分布密度;同时,通过多种地球物理方法联合反演相互约束可以给出较为严格的地球物理模型,并来降低了地球物理反演和解译的多解性,这是地球物理探测研究的趋势,也是天然地震波速层析成像方法的研究趋势。     

地震层析成像技术在黄花寨电站工程勘察中的应用

在受地形条件限制,开展地面物探勘察工作困难的地区,充分利用已有的平硐或钻孔地质工程,采用地震透射波层析成像技术进行勘察较为有利,勘察成果精度较高。文章结合工程实例,介绍利用地震层析成像技术查明岩溶、断层破碎带、强风化软弱夹层方面的应用。     

井间地震层析成像技术在煤层气压裂监测的应用

大1-5井和大1-1井是沧县境内的两口煤层气井,为提高产能,增大气体解吸速率,对其进行了压裂施工.为测定压裂效果,使用DST-3井中声波探测系,对大1-1与大1-5两口煤层气井在压裂前后分别进行了地震层析成像测试,层析成像结果显示,压裂后煤层波速有明显下降,且在横向上变化均匀,表示压裂液扩散带基本连通,裂缝发育,压裂效果明显.为了验证层析成像的结果,将煤层气井的测井解释结果与层析成像结果做了对比,结果较吻合.     

小波多尺度井间地震层析成像方法

将小波多尺度分析的思想引入到井间地震层析成像非线性反问题研究, 首次提出了小波多尺度遗传进化井间地震层析成像方法.该方法是一种非线性全局寻优算法, 其解大大地优于线性化反演方法的解,并极大地提高了地震层析图像的分辨率和图像质量,很好地解决了复杂模型和大扰动模型成像的难题.另外,小波多尺度反演方法还能够提供不同分辨率的反演图像,将有益于层析图像的解释.数值模型试验和实际工程应用结果表明该方法具有很好应用效果.     

Integration of Tracer Test Data to Refine Geostatistical Hydraulic Conductivity Fields Using Sequential Self-Calibration Method

On the basis of local measurements of hydraulic conductivity,geostatistical methods have been found to be useful in heterogeneity characterization of a hydraulic conductivity field on a regional scale. However,the methods are not suited to directly integrate dynamic production data,such as,hydraulic head and solute concentration,into the study of conductivity distribution. These data,which record the flow and transport processes in the medium,are closely related to the spatial distribution of hydraulic conductivity. In this study,a three-dimensional gradient-based inverse method-the sequential self-calibration (SSC) method-is developed to calibrate a hydraulic conductivity field,initially generated by a geostatistical simulation method,conditioned on tracer test results. The SSC method can honor both local hydraulic conductivity measurements and tracer test data. The mismatch between the simulated hydraulic conductivity field and the reference true one,measured by its mean square error (MSE),is reduced through the SSC conditional study. In comparison with the unconditional results,the SSC conditional study creates the mean breakthrough curve much closer to the reference true curve,and significantly reduces the prediction uncertainty of the solute transport in the observed locations. Further,the reduction of uncertainty is spatially dependent,which indicates that good locations,geological structure,and boundary conditions will affect the efficiency of the SSC study results.     

穿越冈底斯地体的宽频地震探测研究

青藏高原是大约60 Ma以来印度次大陆与欧亚大陆直接碰撞形成的,是研究大陆碰撞过程和发展板块构造理论的最佳场所。冈底斯构造带位于印度次大陆与欧亚大陆碰撞的前沿地带,对冈底斯构造带的探测结果将直接影响到对大陆碰撞过程和整个青藏高原地壳变形过程的认识。2011年9月至2012年9月一条穿越冈底斯(GDS)地体的地震深部探测剖面始于班公怒江断裂带北缘,向南穿越了崩错—嘉黎断裂带、冈底斯地体、雅鲁藏布缝合线并跨过藏南拆离断层系(STD),终止于喜马拉雅山南坡。本文作者利用天然地震体波完成了该条剖面的二维走时残差反演,展现出了该地段深部构造格局。首先验证了冈底斯地体浅部存在大面积部分熔融层的研究结论;支持甲玛大型斑岩铜矿为大陆碰撞挤压条件下岩浆上侵的成矿模式;PKP曲线描绘出了本次研究区间内Moho界面的形态,确定地壳最厚处在雅江缝合线南北两侧约50 km区间。这些推论和发现为青藏高原深部的结构研究提供了重要信息。     

地质灾害井间地震层析成像研究

地质灾害体如岩溶、陷落柱、软弱层等的井间地震层析成像属于复杂模型或大扰动异常体的非线性成像，该文首次将小波多尺度思想纺入到蟛间层析成像，建立了小波多尺度井间地震层析成像方法，很好地解决了非线性成像的难题，大大地提高了图像的质量和分辨率，数值模型试验和实际工程应用证实了该方法的实用性和良好效果。     

Studies on the Velocity Structure of Crust-Upper Mantle beneath Eastern Qinghai-Tibet Plateau Using Seismic Tomography

l.IntroductionAteleseismicprofilingwasconductedjointlybytheChineseAcademyofGeologicalSciencesandtheInstitUteofGeophysicsandInnerTectonics,JosephUniversity,France,alongthemainroadfromGonghetoYushuinQinghai,withanarrayof4Othree-componentMinititanstationsandl3one-componentCEISstations,fromJunetoNovember,1998.ThestUdycoversahugearearangingfromthenofthoftheBangong-NujiangFaulttothesouthoftheMid-QilianFault,andfromtheeastoftheQaidamBasintothewestoftheLongmenShanFault,goingthroughSouthQ…     

中国东北地壳结构的地震层析成像

中国东北地区自晚古生代晚期以来,受古亚洲洋、蒙古—鄂霍茨克洋、太平洋构造域的叠加作用,壳幔结构极为复杂。本文收集中国东北地区国家地震台网接收的100 980个P波和91 030个S波到时数据,采用地震走时层析成像方法获得了该地区地壳P波和S波速度结构,进而获得了泊松比结构,用以探讨复杂的地壳结构。成像结果显示：中国东北地区地壳地震波速度结构呈明显的横向不均匀性,不同构造单元和构造单元内部都存在不同程度的不均匀性。松辽盆地整体上浅层地壳以低速异常为主,尤其是S波速度,但部分区域分辨率较低,中下地壳存在较大范围高速异常,推测与太平洋俯冲、后撤导致的岩石圈拆沉和热物质上涌等动力学过程有关;北部的大兴安岭重力梯级带和长白山一线主要表现为低速异常,表明具有大范围的岩浆作用,广泛岩浆作用为固体矿产资源的形成提供热源或物源;长白山、五大连池等近代活动的火山下方部分地壳区域均表现了较强低地震波速度和高泊松比异常结构特征,表明仍存在活动的可能。     

高阶统计量方法在地震信号分析中的应用

高阶统计量分析是近20年来国内外信号处理领域的一个前沿课题,广泛应用于所有需要考虑非高斯、非最小相位、有色噪声、非线性或循环平稳性的各类问题中。在地震信号处理方面,应用高阶统计可以消除高斯有色噪声的影响和提取与识别非最小相位子波;基于高阶统计特征的独立分量分析己成为信号处理领域的一个研究热点并应用于地震信号分析中。对高阶统计量的定义和性质以及高阶谱时频分析方法作了介绍,并以此为理论依据,进行了理论模型和实际地震数据的实验。     

矿体统计分析预测在粤西河台金矿的应用

[摘 要]矿体统计分析预测以空间上有一定分布规律的找矿信息为研究对象,通过对其进行结合地质实际的统计分析,并将统计分析的结果合理地应用于已知矿体向未知矿体的找矿预测。预测的区域是地质上可靠、统计学上发生概率高的有利区域。其预测思路可分为:(1) 研究并发现有一定规律的找矿信息;(2) 结合地质成矿过程的统计分析;(3) 结合地质实际的高概率预测。本文以粤西河台金矿为例,论述了矿体统计分析预测的的思路与方法。由矿体统计分析预测获得的预测区域与钻孔的见矿位置一致,说明其预测是有效的。该方法可能对矿体在空间分布上有一定规律的矿床都有一定的预测意义。最后,总结了矿体统计分析预测的优点、不足、注意事项及应用前景。     

大别山超高压变质带层析地震调查

１９９７年３月中德合作进行了大别山科学钻探选址区层析地震调查,研究结果揭示出大别山超高压变质带（ＵＨＰ）地壳精细结构。郯庐断裂带近垂直延伸至Ｍｏｈｏ界面（可能更深）,在Ｍｏｈｏ界面以上郯庐断裂带西侧大别山地壳物质没有迁移进入其东侧。在主测线（横中至潜山镇）２０ｋｍ深度发现一个由西向东倾斜的强反射层,推测可能是一个大的滑脱层。超高压变质岩石（或地幔物质）可能由地幔深处通过郯庐断裂带再沿此滑脱层析返到     

New Insights into the Mesozoic Large-scale Intra-plate Magmatism and Mineralization in South China from Seismic Tomography

A great amount of new S-wave data has been combined to image the mantle structure down to lower mantle depth near the southeastern margin of Eurasia and understand the tectonics in South China since the Mesozoic. Our results reveal a large-scale structure beneath the South China Sea, with a prominent, broad low-velocity feature of at least 1500-km wide in and below the mantle transition zone(MTZ) and a pronounced low-velocity feature of nearly 500-km wide in the lowermost mantle. Together these ...     

地震沉积学探讨及应用

地震沉积学是在油气勘探开发的需要下产生的,具有鲜明的技术特色和良好的应用前景。文章阐述了地震沉积学的概念和学科特点,认为地震沉积学可以按研究尺度分为地震地貌学和储层地震学,从应用角度提出了地震沉积学的研究思路,并首次提出最小等时研究单元的概念,即三相（地震相,测井相,岩芯相）结合研究时井震统一的尺度,是沉积分析时一个最小的地质成图单元。文章选择鄂尔多斯盆地塔巴庙D气田上古生界岩性油气藏为例,阐述了地震沉积学分析技术在沉积相分析方面的应用方法,展示了地震沉积学研究技术在建立精细等时地层格架,岩相物理分析,多属性地震相分析等方面良好的学科优势。     

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。     

Scales of Reservoir Heterogeneities and Impact of Seismic Resolution on Geostatistical Integration

Seismic measurements may be used in geostatistical techniques for estimation and simulation of petrophysical properties such as porosity. The good correlation between seismic and rock properties provides a basis for these techniques. Seismic data have a wide spatial coverage not available in log or core data. However, each seismic measurement has a characteristic response function determined by the source-receiver geometry and signal bandwidth. The image response of the seismic measurement gives a filtered version of the true velocity image. Therefore the seismic image cannot reflect exactly the true seismic velocity at all scales of spatial heterogeneities present in the Earth. The seismic response function can be approximated conveniently in the spatial spectral domain using the Born approximation. How the seismic image response affects the estimation of variogram. and spatial scales and its impact on geostatistical results is the focus of this paper. Limitations of view angles and signal bandwidth not only smooth the seismic image, increasing the variogram range, but also can introduce anisotropic spatial structures into the image. The seismic data are enhanced by better characterizing and quantifying these attributes. As an exercise, examples of seismically assisted cokriging and cosimulation of porosity between wells are presented.     

相对位移反分析的DFP优化方法及其工程应用

洞室围岩的某些参数,如弹性模量、强度参数等,对地下洞室的施工和设计具有极其重要的作用,直接进行这些参数的现场测量势必要耗费大量的物资和精力,在这种背景下,位移反分析的工程应用具有很重要的理论和实用价值。但洞室工程中大量不确定性因素的存在使得监测结果不可避免地存在随机性,有时会使得变形监测结果产生较大的误差,甚至失真。因此以监测结果的绝对值所反演得到的参数可能是错误的。在这种情况下,以监测数据的相对值进行参数反演在一定程度上可以消除测量误差。基于相对位移的随机反分析法并结合DFP优化算法开发了基于相对位移的随机反分析法,将其应用于一具体洞室工程中反演其弹性模量取得了较为理想的效果。     

Empirical Orthogonal Functions Analysis Applied to the Inverse Problem in Hydrogeology: Evaluation of Uncertainty and Simulation of New Solutions

To fulfil the need to generate more realistic solutions, stochastic inverse simulations in hydrogeology are now constrained on both piezometric head and hydraulic conductivity data. These inverse techniques, often based on geostatistics, allow modifications of an initial solution conditioned only on hydraulic conductivity data to arrive at a final solution that also matches observed heads. By repeating the process as many times as necessary with different initial solutions, one generates an ensemble of final solutions thereby addressing the uncertainty of the inverse problem. This requires a method able to handle the whole ensemble and to work on its relevant characteristics. From this standpoint, the analysis by Empirical Orthogonal Functions (EOF) appears promising. The method builds an orthogonal decomposition of the covariance matrix, calculated over the whole set of solutions, and the areas in space where the first functions have a greater influence corresponding to locations of maximum uncertainty in the solutions. These locations depend both on the hydraulic characteristics of the flow problem and on the spatial distribution of available data. The EOF analysis is used on a synthetic problem that mimics a possible behavior of the Culebra aquifer of the Waste Isolation Pilot Plant (WIPP, New Mexico). The method also allows new solutions to be generated at lower computational cost by a random composition of the functions obtained by the EOF analysis. These new solutions keep the main characteristics of the initial ensemble and because they can be conditioned, they return very good results when they are used to solve the direct problem.     

地震相分析及其在石油勘探中的应用

地震相分析是根据地震资料解释环境背景和岩相,其目的是进行区域地层解释,确定沉积体系、岩相特征和解释沉积发育史,最后预测有利生油区和储集相带。针对传统地震相分析中一些信号分析理论存在的不足,文章介绍了6种新的地震相分析方法及其在石油勘探中的应用实例。