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W.J.Ostrander等人利用砂岩含气泊松比降低到0.1左右时,反射系数随入射角增大而增加的性质,提出了叠前振幅分析直接指示气田的方法。当含气砂岩层的厚度比波长小时,由于层内多次反射的影响,反射系数与入射角的关系呈现复杂的特性。本文系统地计算了不同泊松比和层厚时的反射系数谱,并针对特定的地震子波计算相应的反射波。由反射波极大振幅所作的大量曲线表明,不同的入射角范围、不同的层厚,含气砂岩与非含气砂岩的反射波及大振幅的差别是不同的。W.J.Ostrander等人提出的叠前振幅分析技术指示气田的准则的使用是有一定限制的,要成功地使用叠前振幅分析技术,必须根据具体的地质条件设计相应的模型进行正演计算,以获得叠前振幅资料的解释准则。
W.J.Ostrander et al. By using the property that the reflection coefficient increases with the incident angle when the gas-bearing Poisson’s ratio of sandstone is reduced to about 0.1, a method of direct indication of gas field by prestack amplitude analysis is proposed. When the thickness of the gas-bearing sandstone layer is smaller than the wavelength, the relationship between the reflection coefficient and the incident angle shows complex characteristics due to the multiple reflection in the layer. This paper systematically calculates the reflection coefficient spectrum with different Poisson’s ratio and layer thickness, and calculates the corresponding reflected wave for a specific seismic wavelet. The large number of curves made by the maximum amplitude of the reflected waves show that the difference between the reflected wave and the large amplitude of the gas-bearing sandstone and the non-gas-bearing sandstone is different for different ranges of incidence angles and different layer thicknesses. The prestack amplitude analysis technique proposed by WJOstrander et al. Is limited by the use of the gas field guidelines. To successfully use the prestack amplitude analysis technique, the corresponding model must be designed according to the specific geological conditions for forward calculation to obtain Prestack amplitude data interpretation guidelines.