【作者】 杨宁；

【导师】 贺振华；

【作者基本信息】 成都理工大学 ， 地球探测与信息技术， 2011， 博士

【摘要】 地震勘探中的各向异性主要是指地层中传播的地震波速度随传播方向的变化而变化。现今,各向异性是影响地震成像的一个关键因素。特别是近几年随着我国油气资源的急缺,国家对能源的开发和利用提出了更高的要求。油气地球物理勘探的趋势已经从常规能源石油、天然气到非常规能源煤层气、油页岩、页岩气等领域;其勘探深度从中层逐步向中深层方向发展。上述几类油气地球物理勘探的发展都不可避免的遇到地震各向异性的问题。引起各向异性的因素主要有地震数据炮检距大小,沉积环境以及地震波长与层厚之间的关系等等。这些可通过理论上的各向异性波场数值模拟进行分析和研究,以提高地震成像的精度,有利于后期地震解释工作。各向异性介质波场模拟方法中,单程波动方程数值模拟是一种较为重要的方法。单程波动方程方法模拟的地震波场虽然包含的波场信息不够丰富,但是其模拟的地震波场走时准确、信噪比高;并且,由于仅考虑地震波传播过程中的上行波或下行波,其算法简单,计算速度快,利于快速直观地分析目标地质体的地震反射特征。因此本文就弱各向异性单程波的地震数值模拟方法进行以下研究:1、弱各向异性傅里叶有限差分方法数学推导以及误差分析分析在弱各向异性条件下VTI、TTI介质的频散关系式,并利用有理多项式对频散关系式进行近似处理。在此基础上提出了qP波扩展A-PSPI+SSF方法和qP波优化傅立叶有限差分法。最后利用上述方法进行各向异性和各向同性介质地震波场数值模拟和偏移结果的对比研究,证明了该方法的正确性与实用性。2、正演模拟参数化方法研究各向异性地震模型参数通常包含三个以上的数据体,然而伴随着数据体数量增多带来的问题也就越多:比如有的参数在数据体中横向变化强烈,如果直接应用于模型正演,在追求高精度的情况下需要选用大量的背景参数进行计算,这样会导致计算量成指数级增长;有的参数构建模型过程中由于网格较大,块体间接触界面不够平滑,易成锯齿状结构,在波场的模拟中会导致许多小的绕射,不利于后期的地震响应特征分析。针对以上问题,本文提出了基于K均值聚类的参数优选法,以及基于构造张量的参数平滑与增强方法,并以具体实例说明其优劣。3、起伏地表弱各向异性单程波叠前正演方法在惠更斯理论以及数字检波器原理的基础上,本文提出了基于控制矩阵的起伏地表各向异性单程波叠前正演方法。根据模型试算的结果进行对比分析表明,该方法不仅计算速度较快,而且参数选取灵活,有较好的应用前景。更多还原

【Abstract】 Seismic anisotropy refers to seismic wave propagation velocity changes with the propagation direction.Nowadays, the anisotropy of seismic becomes a key factor in seismic imaging. In recent years, as the lack of oil and gas resources has affected the development of China, a great concern to the exploration of unconventional oil and gas resources is given. The anisotropy become the inevitable problem in geophysical exploration of unconventional oil and gas resources. Many factors causing anisotropy include seismic data offset, sedimentary environment, and the relationship between seismic wavelength and the thickness, and etc. The accuracy of seismic imaging can be improved by the anisotropic wave field numerical simulation and analysis.One-way wave equation is one of the most important anisotropic seismic wave field simulation methods. Although the seismic wave field information based on the method is not rich, it possessed wave field with higher S/N ratio, higher calculating efficiency and applicability in the seismic reflection analysis.The paper has the following innovations:1. Fourier finite difference method for weakly anisotropic mathematical derivation and error analysisWhich analyze VTI, TTI media dispersion relationship, and approximates dispersion relation by using rational polynomial. The A-PSPI + SSF method and optimal Fourier finite difference method of qP wave was proposed in the paper. Finally, the numerical simulation of seismic wave field demonstrate its correctness and feasibility.2. The parameters preferences in the forward modelingThe model parameters in seismic anisotropy simulation usually contain three or more data volumes. With the number increasing of data volume, it will be encountered two problems. Firstly, because of the lateral variation of the parameters, we must choose a large number of background parameters in simulation, which will lead to exponential growth in computing complexity. Secondly, if the interface of the media is not smooth, the simulation will produce much weak diffraction wave in the wave field. In order to improve such problems, an parameters optimization based on K-means clustering, and parameters smooth and enhancement based on the structure tensor were proposed in the paper.3. Prestack forward modeling of seimsic fields in weak anisotropy media by using one-way wave equation from rough surfaceBased on the Huygens theory and principles of digital geophone, one-way wave anisotropic prestack forward modeling method was proposed. The results of model-based simulation show that the method has higher calculating efficiency and extensive suitability.更多还原