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对振幅随偏移距变化的分析来说,研究各向异性介质中的P波反射系数是重要的。直接对反射系数做数值估计时,数值解不能从解析角度反映各向异性对AVO特征的影响。 为解决这个问题,本文为计算具有垂直对称轴的横向各向同性介质中水平边界的P波反射系数提供一种改进了的近似方法,其解中有一个与以前文献中方程相同的描述反射系数低次项角度变化的AVO梯度项,但对大入射角来说,这个解更为确切。这样,精细的近似可以扩展到具有水平对称轴的横向各向同性(HTI)介质。这种情况通常是由一组垂直裂缝所引起的。对比HTI介质的两个垂直对称平面中入射P波的近似反射系数可以看出:AVO梯度的方位变化是横波分裂参数γ和各向异性参数的函数。其中,各向异性参数描述在具有对称轴的垂直平面中近似垂直传播的P波各向异性。
For the analysis of amplitude variations with offset, it is important to study the P-wave reflection coefficient in anisotropic media. When the reflection coefficient is directly estimated, the numerical solution can not reflect the effect of anisotropy on the AVO characteristics from the perspective of analysis. In order to solve this problem, this paper provides an improved approximation method for calculating the P-wave reflection coefficient at the horizontal boundary in a transversely isotropic medium with a vertical axis of symmetry. In the solution there is an equation describing the same reflection coefficient The AVO gradient term for low order term changes, but for large angles of incidence this solution is more exact. In this way, a fine approximation can be extended to transversely isotropic (HTI) media with a horizontal axis of symmetry. This situation is usually caused by a set of vertical cracks. Comparing the approximate reflection coefficient of incident P wave in two perpendicular symmetry planes of HTI media, it can be seen that the change of orientation of AVO gradient is a function of shear wave splitting parameter γ and anisotropy parameter. Here, the anisotropy parameter describes the P-wave anisotropy that propagates approximately perpendicularly in a vertical plane with an axis of symmetry.