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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。
Taner et al. (1979) described the low-frequency seismic energy just below the reservoir as seismic low-frequency companion and concluded that seismic low-frequency companion can be used as one of the hallmarks of identifying oil and gas reservoirs on seismic records. However, the mechanism of generating low frequency companion remains unclear. In order to further explore its mechanism, the author uses a two-dimensional dispersion-viscous wave equation to simulate the seismic model of the geological model containing the gas layer and considers the velocity dispersion effect of the seismic wave in the wave field continuation process. After doing the time-frequency spectrum analysis and extracting the common-frequency profile for the simulated seismic records, we found the low-frequency strong energy of the earthquakes beneath the gas layer. The simulation results show that the strong absorption and attenuation of the high-frequency components of the gas-bearing layer in the seismic signal spectrum are the main causes of low frequency companion. It provides a basis for interpretation and application of low frequency companion with earthquake. The article also gives examples of the application of low-frequency seismic video. The example shows that when the seismic data has a high signal-to-noise ratio, the presence of the oil and gas reservoirs and their spatial distribution can be determined by using the low frequency associated with the earthquake.