基于多分量的井间地震纵横波分离方法研究

1、基于多分量的井间地震纵横波分离方法研究        【中文摘要】井间地震技术作为一项特高分辨率的勘探技术,在油气开发与生产中将发挥越来越重要的作用。在井间地震资料处理技术中,主要有直达波旅行时层析成像技术,和井间地震反射波成像技术。在传统的这两种处理技术中大多都只是利用了纵波信息,而对横波的研究比较少。这一方面是由于对横波的重要性熟悉不够;另一方面是横波本身的复杂性,由于横波能量一般比纵波低,一般被纵波给覆盖,不轻易提取。在地震勘探已由单纯的构造勘探发展到构造岩性勘探的今天,现代已拥有的技术水平可以解决横波面临的

2、一些题目了。假如我们能较为正确地获得横波资料,就能获得井间介质横波速度的二维分布以及高分辨率横波叠加剖面。这对于研究地层的物性(岩性、孔隙度、流体成分等)是十分重要和有利的。而目前常用的波场分离法都是对地面多波记录的,很少涉及到井间激发的情况。因此,寻求适合井间地震资料的纵横波分离方法就成了井间地震处理技术中的关键。本文从井间地震资料的特征出发,对于井间多分量地震资料的纵横波分离,分离步骤基本如下:首先,对多个分量数据进行滤波处理,消除管波等相干干扰波,假如是三分量数据,还得由矢量合成法将其转化为二分量数据;接着,对水平分量和垂直分量进行上下行波的分离;再分别对上行波和下行波,由两分量计算出偏

3、振角,将偏振角应用到波场分离矩阵,就能分离出上下行波各自的纵横波;最后,将上行波的纵波和下行波的纵波相加得终极的纵波剖面,将上行波的横波和下行波的横波相加得终极的横波剖面。对于上下行波的分离,采用频率空间域-p变换,计算中采用广义逆和-p域中的修边处理能极大压制假频和端点效应,采用奇异值分解法能大大进步计算效率。对于偏振角的求取,采用协方差矩阵法,这种方法不需要任何速度等先验信息,只需要输进分离后的二个分量的上行波(或下行波)即可。在构建协方差矩阵时,时窗的选取是一个很重要的因素,本文给出了道自相关法和过零点法。将偏振角应用到由井间地震资料的偏振分析得到的波场分离矩阵上,也就是采用偏振旋转变换

4、,就能分离出纵波和横波。对理论水平层状模型和实际测井资料模型上模拟出的记录进行试算表明:在终极得到的纵波剖面里,横波能量明显减弱,纵波得到保存。在得到的横波剖面里,直达纵波等纵波成分得到极大的压制,原先被纵波能量掩盖的横波成分显现出来,清楚可见。因此,本文给出的纵横波波场分离法对于井间地震多波资料取得了良好效果,该方法充分利用了地震波的偏振特性和视速度特性,计算效率高,抗噪能力强,而且稍加修改,还能应用到地面和海上多分量地震资料中。');【Abstract】 Crosswell seismic technique as a high resolution exploring techn

5、ique becomes more and more usefull in the petroleum exploitation and produce.In the crosswell seismic data processing, we mainly use the seismic tomography with directed wave and obtain high resolutional stack section with reflected wave.In traditional processing techniques of the two methods,we gen

6、erally use the s-wave only,not considering the s-wave.One side,it's caused by our inadequate understand on S-wave,on the other hand,s-wave is more complicated than p-wave. The energy of the s-wave is very low and is covered by p-wave,so we can't extract s-wave from multiple waves easily.Toda

7、y,the seismic exploration has developed from single structure exploration to structure lithology exploration,and we now can resolve a few problems about S-wave.If we can obtain the s-wave data from originality wavefield exactly,then we can obtain the S-wave velocity field of the medium between the s

8、timulate well and receive well.This is very important and usefull to investigate the physical property of the stratum(lithology,porosity,fluid component,et al.).So,the separation of s-wave and s-wave from crosswell seismic data is absolute significant in the crosswell seismic processing.This article

9、 is based on the characteristic of the crosswell seismic wavefield,and give the steps of the separation of p-wave and s-wave.Firstly,make filtering techniques on originality multi-component data,and we can eliminate many coherent interference waves.If the originality seismic data is three components

10、,we should transform them to two components using vector synthesis method.Secondly,with the vertical component and horizontal component,we must separate the down-going wave from up-going wave.Thirdly,with the separated down-going wave and up-going wave,we can calculate the polarization angle by cova

11、riance matrix.Fourthly, applying the polarization angle on the wavefield separation matrix,then we can separate the s-wave from p-wave for both up-going wave and down-going wave.Lastly,adding the up-going s-wave and down-going s-wave as the final s-wave,and adding the up-going p-wave and down-going

12、p-wave as the final p-wave.When separating the up-going wave from down-going wave,we use the frequency-space domain-p transform.The using of generalized inverse and the trimming treatment can suppress false frequency and port effect effectively.Using the singular value decomposition method,we can im

13、prove calculation efficiency obviously.We found the covariance matrix to calculate the polarization angle.This technique don't need velocity information,and we should justly enter the the up-going wave and down-going wave of two components.When founding the covariance matrix,the choosing of the

14、time window is very important,and this article introduce two ways to choose the time window,the autocorrelation and passing zero point.Then,we found the wavefield separation matrix,and put the polarization angle in it,which is calculated above.We call this method for polarization rotation,and after

15、this,the separation of p-wave and s-wave is complete.The tests on the stimulant theoretically crosswell seismic data and practicality data denote:in the final p-wave profile,the energy of s-wave is subdued,and the p-wave is reserved,in the final s-wave profile,the great mass of p-wave is eliminated,and the s-wave which is formerly covered by p-wave appears out distinctly.In the article,the method to separate the p-wave from s-wave for crosswell seismic data works effectively.This method ad