【摘要】 Taner等人(1979)将油气储层正下方的地震低频强能量称为地震低频伴影,并认为地震低频伴影可作为在地震记录上识别油气储层的标志之一。但产生低频伴影的物理机制到现在仍不清楚。为进一步探讨其机理,论文作者采用了二维弥散-粘滞型波动方程对包含气层的地质模型进行地震数值模拟,并在波场延拓过程中考虑了地震波的速度色散效应。对模拟地震记录做时间-频率域的谱分析并抽取共频率剖面后,发现了气层下方的地震低频强能量。模拟结果说明含气层对地震信号时频谱中高频成分的较强吸收衰减是产生低频伴影的主要原因。为地震低频伴影的解释与应用提供了依据。文中还给出了地震低频伴影的应用实例。该实例显示,当地震资料具有较高信噪比时,利用地震低频伴影可确定油气储层的存在及其空间分布范围。更多还原

【Abstract】 Strong low-frequency energy beneath a hydrocarbon reservoir is called a seismic low-frequency shadow and can be used as a hydrocarbon indicator (Taner et al., 1979) but the physical mechanism of the observed low-frequency shadow is still unclear. To study the mechanism, we performed seismic numerical simulation of geological models with a hydrocarbon-bearing zone using the 2-D diffusive-viscous wave equation which can effectively model the characteristics of velocity dispersion and transform the seismic data centered in a target layer slice within a time window to the time-frequency domain by using time-frequency signal analysis and sort the frequency gathers to common frequency cubes. Then, we observe the characteristics of the seismic low-frequency shadow in the common frequency cubes. The numerical simulations reveal that the main mechanism of seismic low- frequency shadows is attributed to high attenuation of the medium to high seismic frequency components caused by absorption in the hydrocarbon-filled reservoir. Results from a practical example of seismic low-frequency shadows show that it is possible to identify the reservoir by the low-frequency shadow with high S/N seismic data.更多还原