【作者】 张建亮；

【导师】 王彦春；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2009， 硕士

【摘要】 地震波在地层中的吸收衰减规律研究一直是地球物理学家研究的重要领域之一。在掌握工区地层吸收衰减规律的基础上,我们通过对地层吸收衰减进行补偿,可以使地震波能量在浅、中、深层都得到加强,在地震剖面上的同相轴更加一致,从而提高地震资料的质量,为后续处理打下良好的基础。研究地震波在地层中的衰减机制及影响因素是进行地层吸收衰减规律研究的理论基础。只有明确地层对地震波的吸收衰减机制,并总结出定量的吸收衰减规律,才能进行品质因子反演工作的研究,进而研究地震波能量补偿方法。我们以粘弹性介质吸收衰减规律为基础,首先设计了粘弹性介质中零偏移距VSP记录的合成算法,实现了水平层状粘弹性介质模型上合成VSP记录的正演过程;然后在水平层状粘弹性介质模型的合成VSP记录上,进行了谱比法、质心频移法的算法设计和试验工作,分析认为影响谱比法和质心频移法计算精度的主要因素有:干涉效应、时窗长度以及数值舍入误差,其中,试验结果表明设计算法的固有舍入误差使得到的反演Q值偏大。为克服这些固有误差,我们设计了谱比法和质心频移法的迭代算法,使固有误差逐步收敛,极大地提高了品质因子反演的精度;最后,我们设计了反Q滤波法的能量补偿算法以及其中的Hilbert变换算法,并利用得到的品质因子信息,对合成VSP记录进行能量补偿,检验品质因子反演算法的有效性,为实际VSP资料的品质因子反演工作提供参考。实际VSP资料中影响地震波能量的因素不仅包括介质的非弹性吸收,还包括球面扩散、非零井源距、干涉效应、反射与透射作用等。为克服这些因素的影响,必须对VSP资料进行球面扩散补偿、波场分离等处理,并选择零偏移距VSP记录进行品质因子反演,我们依据工区地质分层和测井施工班报,将VSP测井处的地层划分为若干厚层,分别采用迭代算法进行等效品质因子反演,避免了薄层中发育的短程多次波的影响;然后,使用反Q滤波算法对VSP资料进行能量补偿,检验了等效品质因子反演的有效性。更多还原

【Abstract】 The study on seismic wave attenuation rules in layers have always been one of the most important research fields for Geophysicist. According to the attenuation rules in practical layers, we can offset the absorbed energy to enhance the seismic wave energy at different depths, and make events more consistent on seismic section, which can provide high-quality seismic data for succedent processing. The research on seismic wave energy attenuation mechanism and its influence factors affords the theoretical base for the research on absorption and attenuation rules in layers. We must find out the seismic wave attenuation mechanism in layers and summarize the quantitive absorption and attenuation rules before our study on arithmetic design of quality factor(Q) inversion and seismic energy balancing.According to the attenuation rules in viscoelastic medium, we firstly design the synthesis method for zero-offset VSP record in viscoelastic medium, and actualize the forward course of synthesizing VSP record of horizontal layered viscoelastic medium model; then we carry through the arithmetic design and experiment of spectral ratio method and centroid downshift method on the synthetic VSP record of horizontal layered viscoelastic medium model, and get the conclusion that the main factors influencing the calculation precision of spectral ratio method and centroid downshift method include interference, time window length and rounding error. The experiment result indicate that the inherent rounding error of designed arithmetic lead the inversed Q value greater than the real Q value. In order to overcome these inherent error, we have designed the iterative arithmetic of spectral ratio method and centroid downshift method to make the error converge gradually, which can greatly improve the precision of quality factor inversion; Finally, we have designed the energy balancing arithmetic of inverse Q filtering and the inner Hilbert transform arithmetic, then we have executed energy balancing on the synthetic VSP record, with the gained information of quality factor, and proved the validity of quality factor inversion arithmetic, which have provided reference for quality factor inversion of practical VSP record. The influence factors of seismic wave energy in practical VSP data include not only nonelastic medium absorption, but also geometric spreading, nonzero-offset, interference, reflection and refraction. In order to overcome these influence factors, we must execute geometric spreading compensation, wave field separation to the practical VSP data, and select the zero-offset VSP data for quality factor inversion. Moreover, we have compartmentalized the stratum at the location of VSP logging into several thick layers, according to the information of geologic formation and well logging tour report, and carried through equivalent quality factor inversion with iterative arithmetic separately, which have avoided the influence of short-path multiples in lamellas. Then we use inverse Q filtering method to compensate the seismic wave energy on the VSP data, and examine the validity of equivalent quality factor inversion.更多还原