【摘要】 为了研究在不同储层厚度、储层下部地层反射界面不同深度情况下低频阴影的出现规律及特征,推导了一种三维弥散黏滞型波动方程的频率波数域波场延拓算法,设计了5个不同的含油气地质模型,对各个模型的地震响应进行了数值模拟,再利用广义S变换对模拟的剖面进行瞬时谱分解,分析了各模型的地震响应以及反射能量随频率的变化等.结果表明:储层低Q时、孔隙介质中流体的黏滞性和弥散性等物理性质明显,且油气层达到一定厚度时低频阴影更明显,它可出现在油气层下部的不同深度位置.在8~12 Hz时,油气层为强能量亮点,其下部显示有强能量的低频阴影,即"上强下强"特征,随着频率增高至16~60 Hz时,低频阴影逐渐减弱直至消失,而油气层的谱能量仍相对较强,即表现为"上强下弱"特征.更多还原

【Abstract】 In order to explore the appearance and characteristics of low-frequency shadow(LFS) at different thickness of reservoir and different depth of reflection interface beneath reservoir,a wave-field extrapolation algorithm of a 3D diffusive and viscous wave equation(DVWE) in frequency-wavenumber domain was proposed.Five different geological models with hydrocarbon-bearing bed were designed and the seismic response of the models was simulated using DVWE,and the instantaneous spectral decomposition was performed using the generalized S transform.The seismic response and its reflection energy variation with the frequency of each model were comparatively analyzed.The results reveal that LFS become more apparent when low Q in reservoir,greater diffusiveness and viscousness properties of fluid in porous media.LFS appeared at different depth under reservoir.At 8-12 Hz,the reservoir energy was a bright spot,and a strong LFS was shown beneath the reservoir,i.e."strong reservoir and bright shadow".As the frequency was 16-60 Hz,LFS was gradually attenuated until the shadow gone,while spectral energy of the reservoir wasstill relatively strong,i.e."strong reservoir and weak shadow".更多还原