【作者】 宋俊亭；

【导师】 韩立国；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 随着地震勘探技术的发展,地震勘探的应用范围越来越广泛。地震记录的波场也越来越复杂。这是因为,地震勘探的研究对象已非传统意义上的均匀介质(或层状均匀介质),而是非均匀介质,甚至复杂非均匀介质都越来越多的成为地震勘探的研究对象。所以,非均匀介质波场特征分析研究已经成为地震勘探研究的热门课题。在非均匀介质研究中,散射波场的研究对解决非均匀介质勘探问题具有很重要的指导意义。本文在总结前人对非均匀介质波场研究成果的基础上,讨论了非均匀介质正演方法的优缺点,给出了波动方程积分解的几种形式,讨论了它们的适用条件和限制。讨论了惠更斯-菲涅尔原理在克希霍夫积分中的应用。格林函数法解波动方程,作为一个较为广泛使用的波动方程积分解的方法,在文中作了详细讨论,并验证了它的使用效果,给定了边界曲面和边界条件的限制。通过几个简单模型试验,可以看出,波动方程的积分解在非均匀介质正演方面应该有其特有的优势:那就是能综合考虑非均匀地质体的边界影响,可以计算全波场效应。对非均匀介质波场的分析,本文是通过实际资料来完成的。文中根据栌枞金属矿区的一些资料,构造了几个不同的有关磁铁矿的地质模型。分析了非均匀地质体,在这里即是矿体的形态和组成等对散射波场的影响。针对复杂非均匀介质,论文介绍了随机介质的一些概念和理论。在此基础上,建立了一系列随机介质模型,分析模型特点,讨论了自相关函数、自相关长度和扰动标准差等对随机介质模型的影响。然后对随机介质进行了正演模拟及波场特征研究,通过变换参数,分析讨论了影响随机介质散射波场的因素,得出了关于随机介质的一些结论。但是,在研究过程中也遇到了很多问题,有待进一步解决,这些都在文中进行了详细介绍。更多还原

【Abstract】 Wave field characteristics of non-homogeneous medium in seismic exploration has become a hot topic. Research on the scattered wave field has important significance on solving complex problems of non-homogeneous media. Based on the predecessors research results of the wave field in inhomogeneous media, discuss advantages and disadvantages of forward modeling in inhomogeneous media. We also give several forms of integral solutions of wave equation, discuss their conditions and restrictions. Given Huygens - Fresnel principle in the application of Kirchhoff integral. Green function method for solving wave equation, widely used as a more integral way wave equation, discussed in detail in the text, and verify the effect of its use, given the boundary surface and boundary conditions. Model through a few simple tests can be drawn, wave equation integral solutions forward modeling in the study of non-uniform characteristics of the wave field should have its unique advantages: it is able to take into account the different media in the role of the wave field position, the calculated wave field closer to the theoretical value.Research on the wave field in inhomogeneous media, this paper is accomplished through the actual data. In the paper, using the information of the Luzong arer, constructed several different geological model of magnetic iron ore. Through the analysis of the wave field characteristics in the forward modeling result, we obtained some conclusions about the scattering wave field in inhomogeneous media:First,non-homogeneous media play a important role in scattering wave field, to study non-uniform medium, scattering theory and scattering must have some benefit on understanding the wave field. Second, the distribution of underground metal mine in the non-homogeneous medium model is of a typical representative of non-homogeneous medium.We use Luzong metal mine to complete the forward modeling .Third, through the analysis of scattering wave field characteristics, draw some conclusions: the composition and the shape of the non-uniform media can influence wave field in inhomogeneous media, this is because the composition of non-uniform medium affect its physical properties, the velocity, density, etc., which determine the non-homogeneous medium with the surrounding medium wave impedance difference, then can affect the strength of the scatter wave field generated and distributed. The pattern is not uniform medium because it can affect the scattering of wave propagation path and the distribution of scattered waves, which affect the whole scattered wave field. However, these in this paper is a simple overview. Further study of specific correspondence should be searching.Fourth, the non-homogeneous media, construction also affect the scattered wave field of important factors. Massive ore body in isolation, steep dip, the fault of these geological structures such as dykes better response in the seismic record of the scattering profile can be reflected clearly. However, when these structures became more complex, and a variety of structures exist, the scattered wave field becomes very complex, non-uniform medium wave field in this record out on the difficult to distinguish.Through the study on random medium model and the wave field characteristics , we draw some conclusions on the complex heterogeneous medium and its wave field characteristics. Conclusions on the random medium are:First, elliptical Gaussian autocorrelation function describing the random medium with a single scale smooth features, and exponential and Von Karman-type autocorrelation function descripte the random media with multiple scales, self-similar characteristics, it seems more suitable to simulate the actual non-uniform medium;Second, the correlation length x and z descripte the scale in horizontal direction and depth direction of the random medium;Third, the standard deviation controls the disturbance speed range of the random medium .Conclusions on the scattering wave field characteristics of random media are:First,wave field in random medium is not a traditional reflection wave field, but a scattered wave field ,which need the scattering wave field theory to explain;Second, the size of the autocorrelation length of the random media medium impact the wave field, the bigger autocorrelation length, the more nearly uniform medium wave field. We also found that in the forward modeling, absorbing boundary conditions more conducive to random media, because the effects on the scattered wave field of the absorption boundary are smaller;Third, the source frequency in the random medium forward modeling play a very important role, to get the ideal random media scattering wave field, you must select the appropriate source frequency;Fourth, influence of random media in layered media is not only in the right random medium layer, but also the entire wave field, especially in the medium which under it .Overall, these findings for our study of complex heterogeneous medium and scattering wave field has important significance.In the process of research projects and papers completing also encountered many problems:First, observing system design is unreasonable, because non-uniform body shape affect the scattered wave field, observing system design directly influenced the acceptance of scattered wave field, the traditional system has been observed seismic wave field recorded in the explanation may be heterogeneous geologic body to explain the wrong phenomenon.Second,there is not a perfect mathod to modeling the non-homogeneous medium, all existing methods are mostly based on the homogeneous medium (or layered homogeneous medium).It’s a limitation in study on non-homogeneous media,for the precision is not enough.Third, systematic research on the complex scattering field have not yet done, many studies are applicable for a particular situation, rather than the complex non-homogeneous medium .Use of the previous method is even possible misinterpretation.Fourth, no seismic simulation software for the non-uniform media. This greatly reduces the efficiency of seismic data acquisition and analysis.更多还原