【作者】 谢爱平；

【导师】 李月；

【作者基本信息】 吉林大学 ， 信号与信息处理， 2011， 硕士

【摘要】 地震勘探数据处理中,由于地震剖面中的一次波(有效波)和多次波的性质非常相似,所以很难准确预测出剖面中的多次波,因此要想在地震剖面中有效分离出多次波是地震信号处理中的一个难题。多次波压制的效果不仅影响地震资料的后续处理(如速度分析、偏移成像等),而且也对地震剖面的解释(产生假构造等)造成直接的影响。国内外地球物理学家们长期以来为解决多次波的压制问题经过了不懈的努力,多种压制多次波的方法被提出。但大体可分为两类:一类是基于一次波和多次波在一些特征和性质上存在差别的滤波法;另一类是基于波动方程的预测相减法。虽然所提出的方法都具有一定的实用性,但同时也存在一些不足。如基于Radon变换法压制多次波要想有效滤除多次波,要求有效波和多次波能量在p/q域中能够准确分离,然而实际数据变换到Radon域时,存在严重的“拖尾”现象,这给多次波的有效去除带来了很大的影响。由于实际地震数据的复杂性,在所采集到的地震记录中,有效波和多次波同相轴有可能重叠,在重叠区域处理效果不佳也是许多多次波压制方法普遍存在的问题。本文在传统基于Radon变换法压制多次波的基础上进行了改进,相对于传统基于Radon变换法压制多次波,该方法克服了在Radon域中存在“拖尾”现象而造成不能有效压制多次波,有效信号丢失等问题,且具有较强的容噪能力。其处理过程大致分为以下几步:(1)应用奇异值分解技术对经部分动校正处理后的地震记录进行多次波预测,由于奇异值分解技术不可能准确地估计出记录中的多次波,这样预测的多次波中含有有效波成分,同时在地震记录中仍然残留多次波,因此我们将该预测的多次波作为后续滤波处理的初始多次波模型;(2)应用高分辨率抛物Radon变换将原始地震记录及预测的初始多次波模型变换到抛物Radon域;(3)在抛物Radon域中应用滤波函数进行多次波压制。对于一些比较复杂的实际数据,可以考虑引入多重滤波思想,将前一次滤波处理得到的多次波作为后续滤波处理的初始多次波模型,这样得到的处理效果会更好,但是计算量也将会相应的加大,所以是否进行多次滤波处理,取决于当前滤波处理的效果。通过对合成记录试算和实际数据处理,处理效果表明该方法能够很好的压制多次波,同时对有效波有较好的保幅作用,并且能够压制动校正后记录中残余的随机噪声,在有效波和多次波同相轴交叉部位也具有理想的处理效果。更多还原

【Abstract】 Multiple attenuation is always a hot and difficult problem in processing seismic signal. As the nature of primary significant wave and Multiple on seismic profile is very similar, it is difficult to accurately predict the Multiple of the profile; therefore, how to separate the Multiple is a difficult problem of seismic signal processing. The quality of Multiple suppression not only affects the subsequent processing of seismic data (such as velocity analysis, migration imaging, etc), but also directly affects the interpretation of seismic profile (producing false structures, etc).Over the years, geophysicists at home and abroad have made unremitting efforts to solve the problem of Multiple suppression, proposed a variety of methods to suppress Multiple. Generally they can be divided into two types: one is the filtering method based on the differ of the characteristics and nature of the primary significant wave and Multiple,;the other is predicting subtraction based on wave equations. Although these traditional methods are practical, but there are also some disadvantages,such as the Radon transform, in order to effectively suppress Multiple, requiring the energy of significant wave and Multiple in the p / q domain can be accurately separated, however, when the real seismic data transformed to the Radon domain, there is serious "tail" phenomenon, which gives a great influence on Multiple attenuation. Because the real seismic signal is complicated, there are some overlap section of same phase axis of effective signal and Multiple. However many traditional methods have a generalize deficiency of bad removing Multiple effect in same phase axis overlap section of effective signal and Multiple. A method using a filter function in High Precision Parabolic Radon domain to suppress Multiple is presented in this paper. it improved some traditional way of multiple attenuation based on Radon Transform, Compared with these traditional ways of multiple attenuation, This method overcomes the phenomenon of Radon domain with bad tail, and it obtained a good effect with a high precision. The process of this method in this paper is roughly divided into the following steps: firstly, forecasting Multiple model from partial NMO seismic record by using SVD(singular value decomposition) technique, we make the Multiple obtained by SVD as the initial Multiple model, In fact using such prediction, the Multiple contains effective signal, while effective signal also contains multiple. secondly, transforming original seismic records and prediction model of the initial Multiple to the parabolic Radon domain by using high resolution parabolic Radon transform. lastly, suppressing Multiple by using a filter function in the high resolution parabolic Radon domain. For some real seismic signal is more complicated, we can consider introducing the repetitive filtering thoughts. making Multiple obtained by the last filtering processing as the next time filtering initial Multiple model, the processing effect will be better, but the computation will increase, whether the repeating filtering should be made, it is decided by the preceding treatment effect.Through the process of synthetic signal and real seismic signal, we find that this method can suppress Multiple effectively, meanwhile, it has a good performance on keeping the amplitude of effective signal, lastly, it can also remove the random noise in the profile after NMO and has a good performance in the area that the overlap of primary significant wave and Multiple.更多还原