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本文着重讨论地－井电磁成像的灵敏度,包括不同观测分量、不同观测位置和不同工作频率的灵敏度函数的分布,为成像系统的布置和数据解释提供理论上的指导。 相似文献
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煤矿顶板砂岩水害严重影响着煤矿安全生产,河道砂体的有效识别对煤矿防治水具有重要的意义。基于地震数据识别河道是有效途径之一,但河道砂不是煤矿勘探的目的层,研究程度低,并且在地震数据成像中河道是一种线状、孤立的地质异常体,常被忽略,因此,在煤炭地震勘探中该项技术不够成熟。以淮北地区某矿的高密度地震数据在含煤地层上覆新近系中发现的河道为基础,在抽取8条线变换为常规观测系统后,以不同偏移距和方位角等观测系统参数为对象,对常规观测系统和高密度观测系统在剖面和平面图中的河道成像质量进行讨论。结果表明:0.8倍河道埋深的最大偏移距和全方位方位角情况下对河道成像较为有利,高密度较常规观测系统对河道成像较好,特别是振幅类属性上具有一定优势。 相似文献
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灵敏度反映了观测数据对模型参数变化的响应情况,灵敏度分析可用于考察某种地球物理探测方法对特定地质异常体的分辨能力,或帮助选择合适的探测方法。灵敏度计算也是迭代反演方法中最为关键的环节,它决定了反演的精度与速度,这里对多例典型地电模型（厚覆盖层、低阻覆盖层和高阻覆盖层）的灵敏度进行了计算,得出了该方法对不同模型的各个参数变化的响应。 相似文献
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在地震资料采集过程中,不可避免地会遇到一些障碍区域,如某段区域由于地形特殊性无法放炮而只能放置接收器,在这种特殊观测系统下,若依然只利用一次波作为有效波,可能会出现地下结构成像信息不足。而如果此区域有比较发育的多次波,尝试将多次波和一次波同时作为有效信息用于波场逆向延拓,在震源记录中同时加入一次波和多次波成像所需的震源信息用于正向延拓,并引用2D反褶积成像条件,从而实现多次波和一次波联合成像,获取比常规一次波成像更加丰富的成像信息。模型数据和实际资料测试结果表明,此方法技术可以实现对障碍观测区域成像信息的补充,说明多次波信息在一些障碍观测区域应用的有效性。 相似文献
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郑建波李美艳 《物探化探计算技术》2023,(4):478-483
航空瞬变电磁法以其快速高效的优势已获得广泛应用,然而航空瞬变电磁采样密集,数据量巨大。为了实现航空瞬变电磁观测数据的快速解释,开展航空瞬变电磁快速成像算法研究。利用反函数定理建立成像迭代格式,并在成像过程中考虑发射源高度和观测时间的影响,进而实现航空瞬变电磁全时域全空域快速成像。这里首先给出了全时域全空域成像理论和实现方法,然后对航空瞬变电磁装置进行了介绍,最后建立了典型采空区模型,利用开发的航空瞬变电磁全时域全空域视电阻率成像方法进行数据成像,成像结果与真实模型基本一致,验证了方法的有效性。 相似文献
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《物探化探计算技术》2016,(6)
在对浅地表复杂地下介质层析成像时,由于观测系统局限性及方法本身对特定岩石地球物理属性的不敏感性等因素,造成地球物理反演存在多解性。在地震走时成像中,地震射线数量在低速区域分布较少形成阴影区,造成其对低速区域成像分辨率较低。同时因为观测数据包含干扰信息以及不同反演方法的局限性等因素造成反演结果包含次生假异常。这里主要研究了空间域的L1-norm、L2-norm约束反演及小波域小波系数稀疏约束反演,对比不同反演方式及约束条件对地质模型的分辨能力。通过测试孤立异常模型、层状地层模型、倾斜地层模型,得出三种不同反演方式分别具有对不同特定模型的分辨特性。在实际资料成像中,可以通过使用多种反演方式,对比反演结果合理性以期达到更准确的地质构造解释。 相似文献
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影响海上地震资料品质的关键因素之一就是面向地质目标的地震资料采集观测系统的合理性,目标模型的射线追踪成像能量照明分析是评价观测系统合理性的主要方法。针对莺歌海盆地DF区地质模型,采用三维射线照明技术,快速准确地获得不同观测系统、不同地震船航行方向、不同炮线距、不同激发源数以及不同排列长度下的目标体反射能量分布特征,通过对比优选出了适用工区的面向目标的三维地震采集观测系统。同时指出减少主测线(inline)线距、增加联络测线(crossline)方向的覆盖次数,可明显提高目标靶区的地震资料采集品质。 相似文献
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炮点密度、检波点密度对于成本的影响是比较清楚的,而对于成像效果的影响还不是很清楚.通过研究炮点密度、检波点密度对成像效果影响,认为决定成像效果的是观测系统炮检距属性,并不是单纯的炮点密度高或者是检波点密度高.分析研究表明,在保证观测系统炮检距属性基本保持不变的情况下,适当调整观测系统炮点密度、检波点密度,既有利于施工成本的降低收又可以保证成像质量不变化. 相似文献
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为了更好地分析探地雷达(GPR)叠前逆时偏移算法对实际地下随机分布介质的成像效果,采用随机过程的谱分解和混合型自相关函数理论构建了不同自相关长度的GPR随机介质模型。基于时域有限差分法(FDTD)构建了GPR叠前逆时偏移成像算法,其中FDTD用于计算正传和反传电磁波场,归一化互相关成像条件用于获取逆时偏移成像剖面。在此基础上,利用该算法对两个随机介质模型的多偏移距正演数据进行计算,并与相应背景介质为均匀介质的逆时偏移结果进行对比。结果表明:电磁波在随机介质中散射强烈,反射波扭曲变形、不连续,形成了明显的随机扰动,致使逆时偏移成像剖面的空间分辨率更低,低频噪声更强;自相关长度是影响随机介质中异常体成像效果的主要因素,自相关长度越小,异常体的成像越清晰,自相关长度越大,异常体的成像效果越差,且不易被识别。 相似文献
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G. Swinnen J. W. Thorbecke G. G. Drijkoningen 《Rock Mechanics and Rock Engineering》2007,40(6):577-590
Summary Seismic monitoring from the head of a tunnel-boring machine (TBM) enables improved assessment of the risks associated with
the tunnel-boring process. The monitoring system provides a live image of ground conditions along the trajectory followed
by the TBM and detects local heterogeneities such as boulders, foundations, and other obstacles that commonly pass undetected
using local geotechnical techniques. From a seismic perspective, the underground setting of tunnelling projects places limitations
on imaging capability. The principal limiting factor is the size of the area upon which transducers can be installed. This
limitation requires adjustments to traditional seismic imaging techniques in which a large area is assumed to be available
for attaching the transducers. Recently developed short imaging operators take this limitation into account and are used in
the examples described herein. The unique conditions of tunnelling yield two advantages over traditional settings in terms
of imaging: rotation of the cutter wheel and the lateral progression of the TBM. Rotation of the cutter wheel, upon which
the transducers are installed, provides the opportunity to illuminate obstacles from different angles in different recordings.
Spatial progression of the TBM enables improvement in the illumination of obstacles and the signal-to-noise ratio by combining
recordings from different lateral positions. In this paper, these specific aspects of seismic imaging during tunnelling are
discussed via models that represent different cases encountered in actual tunnelling projects. These case studies demonstrate
the way in which image quality along the trajectory of the TBM is improved over that in traditional settings. In this way,
the risks associated with the tunnelling process can be more accurately assured. 相似文献
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Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales
Rajakumar S. Devarapalli Amina Islam Titly Farhana Faisal Mohamed Sassi Mustapha Jouiad 《Arabian Journal of Geosciences》2017,10(16):361
With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate. 相似文献
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The geological conditions for coal mining in China are complex, with various structural issues such as faults and collapsed columns seriously compromising the safety of coal mine production. In-seam wave exploration is an effective technique for acquiring detailed information on geological structures in coal seam working faces. However, the existing reflected in-seam wave imaging technique can no longer meet the exploration precision requirements, making it imperative to develop a new reflected in-seam wave imaging technique. This study applies the Gaussian beam summation (GBS) migration method to imaging coal seams'' reflected in-seam wave data. Firstly, with regard to the characteristics of the reflected in-seam wave data, methods such as wavefield removal and enveloped superposition are employed for the corresponding wavefield separation, wave train compression and other processing of reflected in-seam waves. Thereafter, imaging is performed using the GBS migration technique. The feasibility and effectiveness of the proposed method for reflected in-seam wave imaging are validated by conducting GBS migration tests on 3D coal-seam fault models with different dip angles and throws. By applying the method to reflected in-seam wave data for an actual coal seam working face, accurate imaging of a fault structure is obtained, thereby validating its practicality. 相似文献
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随着我国油气勘探的不断深入,复杂高陡构造区越来越成为当今油气勘探的重点,现有成像方法无法满足井周高陡构造的成像需求。针对井中高陡构造,地震干涉法基于源检互易定理,对不同检波点处VSP资料进行相关/褶积处理,重构虚拟震源数据,得到以某一检波点为虚拟震源,另一检波点处接收到的虚拟SWP地震记录。根据地震干涉原理,将VSP资料的不同波场成分进行分离,并对不同波场成分进行数学运算来生成干涉道集。通过地震干涉法能够使虚拟观测系统更靠近目标区域,提高对高陡界面的成像分辨率,实现面向井周高陡构造的高精度成像。笔者等先是对地震干涉原理进行理论推导,基于扰动理论对VSP干涉道集的波场成分进行分析,验证了不同波场成分在地震干涉中的作用及虚假同相轴产生原因。引入窗函数滤波器,对远离虚拟源和虚拟检波器的记录进行衰减,压制干涉过程中生成的虚假同相轴。最后利用干涉成像条件对处理后的地震资料进行成像,并用盐丘模型进行数值试算,得到其高精度成像结果。 相似文献
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António Maurício Carlos Figueiredo Carlos Alves Manuel Pereira 《Environmental Earth Sciences》2013,69(4):1471-1480
The aim of this study is to apply X-ray microfocus computed microtomography (μ-XCT), a promising non-destructive 3D microscopy imaging technique, based on measurements of X-ray linear path attenuation coefficient, in order to study a Portuguese travertine, a random heterogeneous geomaterial used in urban heritage constructions. This study evaluates the impact of soluble sulphate salt–induced decay phenomena on texture characteristics at a micrometric scale. This is done to better describing, imaging, measuring and understanding the impact of an artificially induced sulphate-decay process on petrographic/petrophysical properties. A Portuguese travertine was chosen as the object of our study. Its laboratory-induced changes were systematically monitored, using non-destructive techniques, to determine voids (pores + fractures)/matrix fractions and size spectrum evolution based on 3-D images. This investigation demonstrates that the μ-XCT potential constitutes a valid complementary tool when analysing decay processes of complex natural materials in different environmental conditions. It clearly provides suggestive and important qualitative and/or quantitative estimates, at different spatial scales, of environmentally induced stone voids/matrix network spatial structure-texture evolution correlations. Further qualitative/quantitative parameterization assessment and statistical validation will be the next step to be taken on this study. 相似文献
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二维介质速度成像的新方法是基于地震波的旅行时间，由射线路径沿线的速度分布特征所决定的，将二维介质中的速度分布用两个分别以二维空间坐标为自变量的勒让德多项式的线性组合来描述。根据走时积分方程，即可建立地震波走时与其射线路径沿线的速度分布之间的对应关系，进而重建出地震波射线覆盖区域的速度结构。该成像技术是一个迭代过程，且适用于折射波及反射波。 相似文献