非弹性层状介质地震波频变AVO响应模拟及分析

以非弹性层状介质为模型,基于广义传播矩阵理论计算地震波频变反射系数,算法中同时考虑了与频散和衰减有关的地层岩性因素,以及与薄互层有关的地层结构因素.实现了岩石物理模型、反射系数这两个计算过程的"无缝"连接,精确考虑了由复数弹性模量表示的地层非弹性因素,也为在同一反射模型中考虑源于不同物理机制的频散与衰减提供了方法.数值模拟结果验证了算法的有效性和稳定性,计算结果表明,非弹性薄层的反射振幅随频率先增加后减小,不一定表现常规"低频亮点"异常;同时,薄互层条件下的频散与衰减使得地震反射波的频谱以及AVO特征呈现与频率相关的复杂变化.本文完善了频变AVO算法,为含油气储层频变AVO响应的模拟和分析提供了方法.

Modeling and analysis of frequency-dependent AVO responses in inelastic stratified media

We investigate frequency-dependent AVO responses based on a layered model and the generalized propagator matrix method, considering both the effect of frequency and attenuation associated with lithology, and interbeds related to stratified structure. We propose a seamless procedure linking the rock physics modeling and the calculation for reflection coefficients for accurate consideration of complex stiffness by incorporating the fact that the propagator matrix method is implemented in the frequency domain considering frequency variables. This method can also consider distinct mechanism of dispersion and attenuation, because inelasticity of rocks predicted by different models are usually described by frequency-dependent complex stiffness. Results of numerical stimulations indicate that for a dispersive and attenuation layer with finite thickness, reflection amplitude increases and then decreases with frequency which does not present low-frequency anomalies. Meanwhile, frequency-dependent AVO responses show more complicated variations in thepresence of interbedded structure together with the effect of dispersion and attenuation of the strata. Finally, the improved algorithm for the calculation of frequency-dependent AVO responses may help the modeling and analysis of seismic reflections in the presence of dispersion, attenuation and layered structure.