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地震信号的衰减一般是在频域内利用信号功率谱的统计性质进行表征。但是,传统的基于傅立叶变换的功率谱估计方法的分辨率较低,使得衰减估计的精度较低。Wigner-Ville分布是一种重要的Cohen类时频分布,它具有一系列的优良性质,如时频边缘分布性质、好的时频聚集性等。这些性质对信号的时频分析具有重要意义。因此,Wigner-Ville分布为地震信号的衰减估计提供了新的手段。本文首先介绍了Wigner-Ville分布以及能够减少或消除交叉项影响的平滑Wigner-Ville分布,然后,提出了一种基于Wigner-Ville分布的衰减估计方法。在这一方法中,利用Wigner-Ville分布得到的瞬时能量谱中高频段的能量下降速率度量衰减。将这一方法应用到塔中地区奥陶系礁滩相碳酸盐岩储层预测,结果表明,基于Wigner-Ville分布的衰减能够有效地检测出礁滩相带和泻湖区域之间衰减特性的差异。
Seismic signal attenuation is generally characterized by the statistical properties of the signal power spectrum in the frequency domain. However, the traditional Fourier transform-based power spectrum estimation method has a lower resolution, which makes the accuracy of the attenuation estimation lower. The Wigner-Ville distribution is an important Cohen-like time-frequency distribution with a series of excellent properties, such as time-frequency edge distribution, good time-frequency aggregation and so on. These properties are of great importance to the time-frequency analysis of signals. Therefore, the Wigner-Ville distribution provides a new measure for the attenuation estimation of seismic signals. This paper first introduces the Wigner-Ville distribution and the smoothed Wigner-Ville distribution which can reduce or eliminate the influence of the crossover term. Then, a Wigner-Ville distribution based attenuation estimation method is proposed. In this method, energy decay rate attenuation at high frequencies in the instantaneous energy spectrum obtained using the Wigner-Ville distribution is measured. Applying this method to the prediction of Ordovician reef-shoal facies carbonate reservoirs in the Tazhong area, the results show that the attenuation based on the Wigner-Ville distribution can effectively detect the attenuation characteristics between the reef bank facies belt and the lagoon area difference.