【作者】 武银婷；

【导师】 朱光明；

【作者基本信息】 长安大学 ， 地球探测与信息技术， 2008， 硕士

【摘要】 当地震波在地层中传播时,能量的衰减是传播介质非弹性性质的反映。实验已证明,衰减特性对储层岩石的弹性性质和流体性质等反映灵敏。通常,这种介质所固有的衰减特性用品质因子Q值(Quality factor)来描述。另一方面,由于垂直地震剖面( Vertical Seismic Profiling,简称VSP)方法能够深入了解地震波传播的基本特性,在井下不同深度直接观测地震波的变化,帮助了解反射和透射过程,因而被认为是唯一能够提供有价值的地震波衰减资料的来源。本文在对地震波衰减特性及其影响因素分析的基础上,对Q值正、反演过程进行了深入的研究。基于Ganley的正演理论,考虑反射和透射,对法线入射情况下带有衰减的层状地质模型进行了合成地震记录的生成,并与不具有衰减的地震剖面进行了对比,揭示衰减特性造成了地震波能量及主频的降低;另一方面,在对求取Q值的质心频率偏移法(简称CFS)进行理论分析的基础上,对正演零偏VSP模型进行了反演计算,并通过与振幅衰减法、频谱比法等结果的对比,总结出该方法在薄层识别、分层能力、抗界面干扰方面优于上述两种方法,同时也分析了频带宽度、速度选取、震源点位置对反演结果的影响。最后,通过对两组实际资料的处理,证明了CFS方法的实用性和可行性。更多还原

【Abstract】 The energy attenuation of propagation medium shows the nonelastic property during waves propagating in it. Many tests have confirmed that the attenuation characteristics is sensitive to the elastic and fluid property of reservoirs. Generally, Q value, short for Quality factor, is used to show the intrinsic attenuation. On the other hand, VSP, which can thoroughly show the basic propagation characteristic, directly receive seismic waves in the different depthes to help people understand the reflection and transmittion, is regarded as the only way to reply the attenuation from seismic datas.This paper has studied the forward and inverse of Q basing on the analysis of attenuation characteristics and influence factors. Considering the reflection and refraction, the synthetic seismograms of layered attenuation models are generated basing on Ganley’s theory, which is fit for the normal incident. Compared with the unattenuation records, the decreases of energy and frequency display the characteristic of the unelastic models. Secondly, with the discussion on the theory of CFS, short for Centroid Frequency Shift method, the paper inverses the Q value for the forward zero-offset VSP model and compares the results with amplitude attenuation method and the ratio of frequency spectrum method. It shows that CFS is superior in the recognition of thin layers, the separation of multi-layers, the anti-disturbance of interfaces, the adaptation of shot’s location. It also discusses the influence of the frequency band and the choice of velocity used to inverse. Finally, the processing of two field datas reveals its practicality and feasibility.更多还原