厚度小于地震波长的储集层照样可以含有大量碳氢化合物。这类地层表现出涉及到来自储集层顶面和底面反射波干扰的调谐效应。储集层中的天然裂缝在决定流体流时能发挥重要作用,使得人们极大地关注着裂缝的密度和方位。当存在一组或多组线状垂直裂缝时,非零偏移距的各反射波的振幅随方位角而变化;所以,调谐效应也将随方位角而变化。当波长远大于典型的裂缝间距时,等价介质理论保证能把这类垂向断裂地层模拟为镜面对称平面平行于该地层的单斜地层。垂向断裂薄层的反射和透射系数随入射角和方位角的变化可以用水平慢度来表示,并能自动计算穿越地层传播的射线随方位角的角度变化及当地层厚度和波长处于同一数量级时出现的调谐效应。对足够小的频率(或等价地说,足够薄的地层),导出了反射和透射系数矩阵及透射振幅的近似表达式。这些表达式明确表明,所有反射脉冲和所有转换透射脉冲和入射脉冲的时间导数具有相同的波形,而对较厚的地层而言,明显存在着来自于地层顶部和底部的不同反射波,尤其是对小入射角更是如此。当这些反射波相互干涉时,可以发现脉冲波形随方位角发生明显变化,导致了地层中由于传播效应引起的地层顶部和底部反射系数方位角变化方面的差异。 Reservoirs with thicknesses less than the seismic wavelength can still contain large amounts of hydrocarbons. Such strata exhibit tuning effects that involve reflected-wave interference from the top and bottom of the reservoir. Natural fractures in the reservoirs play an important role in determining the fluid flow, so much attention is paid to the density and orientation of fractures. When one or more sets of linear vertical cracks are present, the amplitude of each reflected wave at a non-zero offset varies with azimuth; therefore, the tuning effect will also vary with azimuth. Equivalent medium theory assures that these vertically fractured strata can be modeled as a monoclinic formation with a mirror-symmetry plane parallel to the formation at wavelengths much greater than the typical fracture spacing. The reflection and transmission coefficient of the vertically fractured sheet can be expressed as horizontal slowness according to the change of incidence angle and azimuth angle. The angle variation of azimuthal ray propagating through the formation can be automatically calculated and the thickness and wavelength of the local layer are in the same order of magnitude When the tuning effect. For sufficiently small frequencies (or, equivalently, sufficiently thin strata), an approximate expression of the reflection and transmission coefficient matrix and the transmitted amplitude is derived. These expressions make it clear that the time derivative of all reflection pulses and all converted transmission and incident pulses have the same waveform, whereas for thicker formations there are distinct different reflected waves from the top and bottom of the formation, in particular This is especially true for small angles of incidence. When these reflected waves interfere with one another, it can be found that the pulse waveform changes significantly with azimuth, resulting in differences in the azimuthal variation of the top and bottom reflection coefficients of the formation due to propagation effects in the formation.