As effective criteria for hydrocarbon detection, Amplitude Versus Offset (AVO) technology has been widely used in the recent years. Zoeppritz equation, which describes the reflection and transmission of plane wave on a single interface separating two half infinite spaces, is the basis for traditional AVO analysis. This characteristic of Zoeppritz equation makes it unsuitable to analyze the propagation of wave in multi-layered media when the layers are very thin. This study derives the three-layer media equation based on multi-layer media equation by Breshkovsky in elastic regime for discussing the reflection and transmission of plane wave in thin bed. For that the reflection coefficient is a continuous function of incident angle, frequency and thin bed thickness, it is possible to analyze the AVO effects with varying the incident angle, frequency and thin layer thickness. It is concluded that (1) three-layer media equation is more quantitative and precise than Zoeppritz equation to analyze the AVO responses of thin bed; (2) the influence of thin bed thinning on variations of amplitudes is equal to that of dominant frequency decreasing; (3) AVO analysis of P-S wave helps us to eliminate the problem of multi-solutions in fluids prediction; (4) With decreasing Q (quality factor), the AVO curve obtained from three-layer media equation become more smooth and get closer to the curve calculated by Zoeppritz equation.
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