各向异性介质中P波反射系数

Reflection coefficient of P wave in anisotropic media

分析了横向各向同性和方位各向异性介质的成因及其本构关系。由此讨论弹性波在这两种各向异性介质中的传播特点，并提出了表征各向异性程度的广义各向异性参数，这些参数既可表征横向各向同性介质的各向异性，也可表征方位各向异性介质的各向异性。讨论了两种各向异性介质中存在水平界面时的反射系数，并将横向各向同性介质中的反射系数公式推广到方位各向异性主轴上。根据算例修正了近似式，着重讨论和分析了这两种各向异性介质中的地震波反射振幅与炮检距的关系（ａｍｐｌｉｔｕｄｅｖｅｒｓｕｓｏｆｓｅｔ，ＡＶＯ）以及对实际勘探的影响和指导意义。

The cause of transverse isotropy and azimuthal anisotropy is discussed. The general constitutive relationship and its special froms for the two types of anisotropy are also given. After analyzing the characterizations of elastic waves propagating in this two kinds of anisotropic media, generalized expressions of anisotropy parameters were deduced, which describe the anisotropy degree both in transverse isotropic media and azimuthal anisotropic media. When there is a interface existing in the two anisotropic media, the reflection coefficients are discussed respectively. The formula. is extended to be used in the symmetric plane in azimuthal anisotropic media. Finally, by comparing the exact reflection coefficient with approximations for typical shale and gas sand models and carbonate rock models, the amplitude versus offset (AVO) in the two kinds of anisotropic media and its influence in actual exploration, especially for fractured reservoir are discussed.