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地震波速度求取若干问题研究
【作者】 孙祥娥;
【导师】 周熙襄;
【作者基本信息】 成都理工大学 , 地球探测与信息技术, 2007, 博士
【摘要】 在地震资料的处理过程中,地下介质速度求取的准确与否将直接影响到动校正、叠前或者叠后偏移、剩余静校正量等,从而影响到资料的分辨率,因此获取准确的速度参数是正确处理和解释地震资料的中心问题。随着石油勘探地不断发展,油气勘探新区越来越复杂的地质条件使地震资料的处理更具挑战性:原始地震数据的信噪比偏低,共中心点道集中反射波同相轴不明显,速度谱中没有明显的峰值,给速度分析带来了很大的难度;地下介质的各向异性以及大炮检距的地震数据采集方法使常规速度分析的假设不成立,实际地震波旅行时曲线与双曲线之间的偏差变大,继续采用常规速度分析方法对这些资料进行速度分析必将引起较大的误差。本论文针对这些问题进行了较系统的理论模型和实际应用的初步探讨,并取得了一定的进展。本论文首先研究了地震反射波走时的正演方法,为速度分析提供可靠的研究数据。考虑到本论文重点涉及旅行时描述,速度参数包含在地震波时距曲线中,所以选择了简单准确的最优化射线追踪来实现地震波旅行时的正演计算。在假设任意起伏界面用三次样条函数分段拟合的基础上,本论文提出将全局搜索策略和快速收敛的拟牛顿法相结合,利用全局搜索策略首先得到线性极小化的近似解,然后用布罗依登—弗莱彻—戈德法伯—香农算法实现拟牛顿法,实现了弯曲界面条件下射线走时的正演。针对低信噪比的地震数据,本论文提出了一种新的速度分析判别准则。利用主成分分析的思想,通过分析待分析数据体中第一主成分方差贡献率与其他主成分方差贡献率的大小,达到提取反射波同相轴信息的目的,并利用加权系数降低噪声对第一主成分的影响,提高第一主成分对信号的敏感度,从而提高新的速度判别准则对低信噪比数据的处理能力。标准双曲线反射波走时描述只有在小排列和层状介质假设条件下才是精确的,速度的各向异性会使反射波走时较大地偏离标准双曲线。针对地下介质的各向异性,本论文研究了垂直横向各向同性介质反射波走时特征,对两种非双曲线的反射波地震走时描述方法进行了理论分析。通过模型对比分析,证明了非双曲线反射波时距曲线方程的精度明显高于双曲线时距曲线方程,并提出利用各向异性介质的非双曲线速度分析方法对各向异性介质和长排列地震数据进行速度分析。本论文对提出的各种方法,通过编制的程序进行了实际计算,证实了文中的结论,并通过实际资料的试算,验证了各方法的有效性。
【Abstract】 In seismic data processing, the effects of dynamic correction, pre-stack andpost-stack migration, residual static correction are all based on the accuracy ofmedium velocity, including the resolution of seismic data. So it is the key ofinterpretation and processing of seismic data to get the precise velocity correctly.Seismic exploration in more and more complex geologic condition causes moredifficulty in data processing and brings us more challenge. It is more difficult thanbefore for velocity analysis because that the signal-to-noise becomes lower, thereflection in CMP gather can’t be found clearly, and there are no remarkable focusesin velocity spectrums.Anisotropic medium and data collection by long spreads break up theassumption of the standard velocity analysis, which based on short spreads and layerisotropic medium. So using the standard hyperbolic velocity analysis to process theseismic data of these data must cause big error. Focusing on these problems, thispaper analyzes the existing theories by models, explores their industrial applicationsand made some progress.In order to offer corrective research data for velocity analysis, this paperpresented a new reflection forward method. Based on fitting complex interface bytriple spline function, we combined global searching with Quasi-Newton method.Firstly, using global searching way get the approximate solution of linearminimization, then realize Quasi-Newton method byBroyden-Fletcher-Goldfarbo-Shanno method.For the low signal-to-noise data, this paper presents a new distinguish principleof velocity analysis—the principal component analysis. In this way, the reflection canbe obtained though comparing the ratio of the first principle component to the others.Using weighting coefficient can improve the sensitivity of principal component whilededuce the influence of noise to principle component. The standard hyperbolic approximation for reflection moveouts in layered mediais accurate only for relatively short spreads, even if the layers are isotropic. Velocityanisotropy may significantly enhance deviations from hyperbolic moveout. Foranisotropic medium, this paper analyzes the character of moveout curves of reflectedwave by vertical transverse isotropy, and analyzes the theory of two kinds ofnonhyperbolic reflection moveout by models. It proves that the two nonhyperbolicmoveout methods have more accurate than standard hyperbolic way. At last, thispaper points out the nonhyperbolic way of anisotropic media to analyze the velocityof anisotropic media and long-spread data.These conclusions in this paper have been verified by program. These methodspresented in this paper have been tested against by field data. The data processingresults prove that these methods have more effects than traditional way.
- 【网络出版投稿人】 成都理工大学 【网络出版年期】2008年 02期
- 【分类号】P631.4
- 【被引频次】12
- 【下载频次】1001