基于波场延拓的多次波压制技术及其改进

发布时间：2019-06-06 04:44

【摘要】：多次波衰减是地震勘探资料处理中的一个重要课题[1],多次波的去除效果好坏直接影响后面的数据处理与解释，一个比较明显的例子就是使得重要的地质构造受到屏蔽，不能很好的被揭示出来，而且还有可能导致沉积加厚的错误，进而影响整个地震勘探效果。为了提高地震勘探的效果，识别与压制多次波是一个十分重要的问题。为了消除多次波，首先要找出多次波与一次波差异。多次波的种类有很多，分类方法也有很多种，按照产生的位置来分，有地表相关多次波，层间多次波。顾名思义，地表相关多次波的产生位置位于地表，在海上勘探时，反射面为水面。该种多次波的反射能量较强。层间多次波是指在地下介质层中多次反射产生的多次波。除了上述分类方法，多次波也可以按照周期的长短来进行分类，按照这种分类方法可以分成长周期与短周期的多次波[2]，长周期多次波的特点是具有分离的同相轴，具有确定性的表现特征，在地震数据中能够被很好的识别。与之相反，短周期多次波的产生原因多与地下介质薄层干涉有关，而且相比于长周期多次波来说，短周期多次波极不容易被识别[2]。由于多次波问题的重要性，因此已经引起了众多地震勘探领域研究人员的重视，大量的科研力量投入到多次波问题的研究当中，许多勘探地震学家都致力于多次波压制方面的工作，并且获得了大量的成果。1997年SEG年会上，专门展开了一场讨论就压制多次波问题，随后在1999年，“THE LEADING EDGE”特别开辟了一个压制多次波的专题进行刊登，反映了勘探地球物理学家们对此问题的关注[3]，很多有效的多次波压制方法不断被提出来，并且得到了广泛的应用，成为了地震勘探过程中不可或缺的步骤。这些方法主要分为两类，一类是基于一次波和多次波在空间上的差异，另一类是基于多次波的可预测性和周期性这两个性质。一次波和多次波在地下传播路径上有差异，这种性质使得两者在速度上和反射结构上有了差异，第一类消除方法就是基于这个原理。同样，一次波与多次波是存在内在联系的，可以通过利用显式或隐式的波动方程将他们联系起来，这种方法首先需要预测多次波，这就需要用到一次波，然后再将预测的多次波从原始数据中减去。在这两类方法中，比较普遍应用的有基于时差和倾角差异去除多次波法，预测反褶积去除多次波方法，波场延拓法压制多次波法，SRME方法等等。其中，SRME方法就是利用叠前数据来构建地表相关多次波的，，基本过程就是利用叠前数据本身作为波场延拓的因子，即通过对数据自身进行褶积，由一次反射波产生一阶多次波，这是一种数据驱动的方法，这种方法的优点就是不需要知道地下介质结构的信息，因为地震数据本身做延拓算子，里面已经包含了地下介质结构的一些信息。但是SRME方法存在的问题是但它的缺陷在于实际采样数据很难满足理论要求，尤其是在三维领域。针对SRME方法存在的问题，本文所做的波场延拓方法源于惠更斯原理，将由接收表面的地震波场通过与地下介质各点到水面的格林函数做褶积，将其延拓到海底，然后再延拓回接收平面，即在水层增加了一个传播过程，增加了多次波的阶数，由于该种方法的预测算子是建立在模型基础上的，不受限于震源采样，能够弥补SRME的缺陷。通过结合Curvelet域多次波匹配减去方法，波场延拓技术取得了较好的多次波压制效果。 Curvelet变换作为一种全新的多尺度多方向时频分析方法，具有很好的稀疏性和方向性，其稀疏性令其使用很少系数来准确的描述地震信号，其方向性使得Curvelet变换能够更稀疏的表示图像的边缘,对地震信号有高效的，稳定的，近乎最优的表示。Curvelet变换的一个优势在于有效信号和随机噪声在Curvelet域分开存放，这样即可在提取有效信号的同时，又可以不增强随机噪声与干扰。 Curvelet变换具有的各向异性特性使得其能以最优的程度去描述地震信号；Curvelet变换的方向性使其能够对地震信号信号做精细的处理，即只处理特定角度特定位置的地震信号，对其他信号则可以忽略，这为高精度地震资料处理提供了一种新方法；有效地震信号与随机干扰经过Curvelet变换后，区别极为明显，在进行处理的时后，只需提取有效地震信号，然后去除随机的干扰即可，以此来压制随机噪声，提高数据信噪比。多次波的去除问题固然重要，但是不可忽视的一点就是无论是多次波还是一次波都是经过地下介质反射到地表被接收记录的，因此多次波和一次波一样也包含着大量地下介质的信息，这就为压制多次波的问题提供了一个新的方向，我们不能只关注于去除多次波，还要充分的利用多次波的这种特点，提高地下介质的分辨能力。
[Abstract]:The multi-wave attenuation is an important subject in seismic exploration data processing[1]. The removal effect of multiple waves has a direct effect on the data processing and interpretation. A more obvious example is that the important geological structure is shielded and can't be revealed well. But also can lead to an error of deposition and thickening, thereby affecting the whole seismic exploration effect. In order to improve the effect of seismic exploration, it is a very important problem to identify and suppress multiple waves. In ord to eliminate multiple wave, it is first to find that difference between the multiple wave and the primary wave. There are many kinds of multiple waves, and there are many kinds of classification methods. According to the generated position, there are surface-related multiple waves, and the inter-layer multiple waves. As the name implies, the generation position of the surface-related multiple waves is located on the surface, and the reflecting surface is the water surface at the time of the sea exploration. The multiple-wave reflection energy is strong. The inter-layer multiple-wave is a plurality of waves generated in a plurality of reflections in the underground medium layer. in addition to the above-mentioned classification method, multiple waves can be classified according to the length of the period, and the multi-wave (2) of the growth period and the short period can be divided according to the classification method, And can be well recognized in the seismic data. In contrast, the cause of the short-period multiple-wave is much related to the thin-layer interference of the underground medium, and the short-period multiple-wave is not easily recognized as compared to the long-period multiple-wave. due to the importance of multiple wave problems, the importance of the researchers in many seismic exploration fields has been aroused, and a great deal of scientific research power has been put into the research of many wave problems, many of the exploration seismologists work on the work of multiple wave pressing, and a great deal of results were achieved. In the 1997 SEG meeting, a discussion was devoted to the suppression of multiple wave issues, and in 1999, the "THE LEADING EDGE" opened a special topic for the suppression of multiple waves, reflecting the concerns of the exploration geophysicists on this issue[3], Many effective multi-wave pressing methods have been put forward, and have been widely used and become an indispensable step in the process of seismic exploration. These methods are mainly divided into two classes, one is based on the difference of one wave and multiple waves in space, and the other is based on the predictability and periodicity of multiple waves. The first kind of elimination method is based on this principle. Again, once a wave is intrinsically linked to multiple waves, they can be associated by using explicit or implicit wave equations, which first requires prediction of multiple waves, which requires the use of a primary wave and then subtracts the predicted multiple waves from the original data. In these two kinds of methods, many wave methods, such as multi-wave method, multi-wave method, wave-field continuation method, multi-wave method, SRME method, and so on, are compared to the common application based on the difference of time difference and dip angle. in which, the SRME method uses the pre-stack data to construct the surface-related multiple-wave, the basic process is to use the pre-stack data itself as a factor of the wave field continuation, that is, by the convolution of the data itself, the first order multiple wave is generated by the primary reflection wave, which is a data-driven method, The advantage of this method is that it is not necessary to know the information of the structure of the underground medium, since the seismic data itself is a continuation operator, which already contains some information of the structure of the underground medium. The problem with the SRME method is, however, that the actual sampling data is difficult to meet the theoretical requirements, especially in the three-dimensional field. In order to solve the problems existing in the SRME method, the wave field continuation method in this paper is derived from the Huygens principle, and the seismic wave field from the receiving surface is folded by the Green's function corresponding to the points of the underground medium to the water surface to extend to the sea floor and then to the receiving level. The surface, that is, a propagation process is added to the water layer, and the order of multiple waves is increased. Because the prediction operator of the method is established on the basis of the model, it is not limited to the source sampling and can make up for the shortage of the SRME. In this paper, by combining Curvelet's multi-wave matching subtraction method, the wave field continuation technique has obtained the better multi-wave suppression effect The Curvelet transform, as a new multi-scale multi-direction time-frequency analysis method, has good sparsity and directivity, and its sparsity makes it use very few coefficients to accurately describe the seismic signal. Its directivity makes the Curvelet transform a more sparse representation of the image. The edge of the seismic signal is efficient, stable and nearly optimal. The advantage of the Curvelet transform is that the effective signal and random noise are stored separately in the Curvelet field, so that the effective signal can be extracted and the random noise can not be enhanced. the curvelet transform has anisotropic properties that enable it to describe the seismic signal at an optimal level; the directivity of the curvelet transform enables it to perform fine processing of the seismic signal signal, i. e., to handle only seismic signals at a particular angle-specific location, for other signals, can be ignored, which provides a new method for the high-precision seismic data processing; after the effective earthquake signal and the random interference pass through the Curvelet transformation, the difference is extremely obvious, make random noise and improve The data-to-noise ratio of the data is important, but it can't be ignored, that is whether the multiple waves or the primary wave are reflected from the underground medium to the surface to be recorded, so many waves and one wave also contain a large amount of wave The information of the underground medium provides a new direction for the suppression of the multiple waves, and we can't just focus on the removal of the multiple waves, but also make full use of the characteristics of multiple waves and improve the underground
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.4

【参考文献】