【作者】 刘红爱；

【导师】 雷宛；

【作者基本信息】 成都理工大学 ， 地球探测与信息技术， 2011， 硕士

【摘要】 近年来,多波多分量地震勘探技术研究取得了极大进步,人们对于各向异性现象的了解也更为深入。多波资料比单纯纵波含有更为丰富的地层信息,综合利用纵横波资料可以获取更为详尽可靠的地层参数。当横波斜交穿过各向异性介质(裂缝)时会发生分裂,偏振方向沿裂缝走向时,传播速度快,称为快横波,偏振方向垂直裂缝走向时,传播速度慢,称为慢横波。只有当横波与裂缝方位呈一定的角度时才会发生横波分裂,分裂的快慢横波的强弱与裂缝的强度密切相关。通过对横波分裂现象的分析可以得到裂缝的发育方向和密度等参数,利用这些参数可以更为准确地预测裂缝。当进行纵波源激发的转换波勘探时,下行纵波遇到分界面时会转换成横波,横波在向上传播过程中遇到裂缝时,同样会发生分裂。因此,利用转换横波分裂的快慢横波成为研究裂缝方向及其发育程度的最直接最可靠的方法。将转换波的径向和横向分量数据按照方位顺序排列起来,由于各向异性的影响,径向分量的方位道集存在较大的方位时差,0°到360°的方位数据的同相轴表现为一个“正弦”波形,而横向分量具有较强的能量,并且也表现出了较大的方位时差。在径向分量上“正弦”的波峰代表各向异性(裂缝)的走向,而波谷代表垂直于各向异性方向。研究发现在横向分量上每间隔90°就会发生极性反转现象,极性反转点就代表各向异性方向的变化点。在强各向异性数据基础上,要得到较好的成像剖面,必须进行方位各向异性校正。Alford旋转方法最早用于双源激发的四分量VSP资料,根据SV波和SH波得到快慢横波信息,实现快慢横波分离。这篇硕士论文基于转换横波分裂理论,利用地面宽方位转换波资料,通过构建互相垂直的转换波径向和横向分量对,从而将Alford旋转方法成功用于转换波处理,进而实现地面资料的快慢横波分离。同时,利用宽方位转换波的径向和横向分量资料,完成了多层裂缝介质的各向异性分析。在此基础上,还完成了转换波方位各向异性校正研究,大大提高了宽方位转换波径向分量成像质量。宽方位转换横波分裂方位各向异性校正处理的主要步骤是:首先,根据径向和横向方位数据确定一个浅层分析时窗,在分析时窗内利用Alford旋转方法分离快慢横波。如果有多个方位角数据,则需要分别求取各个方位的快慢横波,然后进行累加。其次,根据快慢横波相似原则,求取快慢横波互相关值,解释角度-时延谱得到各向异性方向和快慢横波时延。然后,将快慢横波时延用于慢横波上,进行时延补偿。最后,根据各向异性方位角,利用反旋转技术将快横波和时延补偿后的慢横波反旋转回原来的径向和横向方向上,得到各向异性校正后的径向和横向分量。这样,就完成了第一层裂缝的各向异性分析,同时还得到第一层的裂缝方向、裂缝密度、补偿后的径向分量等数据。将第二分析时窗内的快慢波数据与第一时窗内的快慢波数据加权平滑拼接。依此类推,在完成浅层时窗的横波分裂方位各向异性校正后的数据上,进行深层数据的分析和处理。在本论文中,根据反射率法正演模拟了横波分裂现象,利用模拟的数据进行了Alford旋转快慢横波分离和方位各向异性校正处理,处理结果表明了方法的正确性。将研究的转换横波分裂方位各向异性校正技术应用于川西XC气田的宽方位三维三分量地震数据处理,不但得到了裂缝参数,而且还消除了宽方位转换波的方位各向异性影响,提高了转换波径向分量的成像质量,达到了研究目的。更多还原

【Abstract】 In recent years, multi-wave and multi-component technology has made great progress, People have made more understanding for anisotropy, Multi-wave data contain more information than single P-wave, Utilization for P-wave and S-wave data can get more detailed and reliable formation parameters. When S-wave is not parallel nor perpendicular through the anisotropic medium (fracture), S-wave splitting occurs .When the polarization direction along the fracture, the propagation speed is faster, named as fast S-wave, when the shear wave polarization direction perpendicular to the fracture, the propagation speed is slow, named as slow S-wave.Only when the wave with the fracture orientation at some angle, S-wave will split, and the strength of splitting is closely related to fracture intensity, and we can get the fracture orientation and density from the analysis of S-wave splitting. These parameters can be used to predict fracture more accurately. When P-waves was uesd to explore, the downgoing and upgoing wave meet the interface will be converted into S-waves. When upgoing S-wave encounters fracture, splitting also occurs. Thus, the use of fast and slow wave splitted from converted S-wave has become into smost direct and reliable method to study the development fracture and its direction.Arrange the radial and transverse components of converted wave together in accordance with the azimuth order, due to the impact of anisotropy, there is a big azimuth time-delay in radial component azimuths gathers, 0 degrees to 360 degrees azimuths datas show form of sine wave; there is strong energy in transverse component, and also show a great azimuths time delay. In the radial component, peak of the sine wave said direction of anisotropy, while trough side the direction perpendicular to the anisotropy; study found that in the transverse component of 90-degree intervals, the polarity reversal occurs, very reversal point represents the change in the direction of anisotropy. Strong anisotropy in the data, to get better imaging section, anisotropy must be corrected.Alford rotation method is mainly used for four-component VSP data by dual-source exploration, according to the SV and SH wave we got the fast and slow wave information and then realize the separation of fast wave and slow wave. This thesis based on converted shear wave splitting theory, using ground azimuth converted wave data, by building mutually perpendicular radial and transverse wave components on which the Alford rotation method used successfully, so as to realize the separation of fast wave and slow wave in surface data. At the same time, by using converted wave azimuth radial and transverse component data, we completed the analysis of multi-layer fracture media. On this basis, we have completed the correction of converted wave azimuthal anisotropy, which greatly improved the azimuth radial component of converted wave imaging quality.Azimuth converted shear wave splitting anisotropy correction contain the next main steps:First, according to the radial and transverse azimuthal data to determine a shallow analysis window, use Alord rotation in the analysis window to seprate fast and slow wave; If there are multiple azimuth data, you need to strike a different direction, respectively, and then accumulate.Secondly, because fast and slow wave are similar, we can get cross-correlation values, and get the anisotropy direction and shear wave time delay by explaining the angle-delay spectrum.Then, the time-delay was applied to slow wave to compensate time-delay.Finally, according to anisotropy azimuth, use anti-rotation technique to make fast wave and slow wave after compensating time-delay to the original radial and transverse direction, then we can get radial and transverse component after anisotropy corrected.These can only complete the anisotropy in first fracture, get the fracture direction in first layer,fracture density, the compensated radial component and other data. The data of fast and slow wave were jointed weighted in first and second analysis window. And so on, to do the deeper data analysis and processing after complete shallow layer analysis.In this paper, we forward modeling shear wave splitting according to the reflection ratio method, not only using modeling data to separate the fast and slow wave, but also do the wave anisotropy correction, and the results show that the method is correct. The research method of converted shear wave splitting anisotropy correction was applied to process 3D3C wide-azimuth seismic data in the XC gas fields in West of Sichuan. Not only the fracture parameters was obtained, but also the azimuthal anisotropy of converted waves was eliminated, and the image quality was increased greatly.更多还原