Seismic attenuation from VSP data in methane hydrate-bearing sediments
Seismic attenuation from VSP data in methane hydrate-bearing sediments
复制标题
含甲烷水合物沉积物中 VSP 数据的地震衰减
DOI：
10.1071/eg07001
复制
发表时间：
2007
影响因子：
0.9
通讯作者：
J. Matsushima
中科院分区：
文献类型：
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作者：
J. Matsushima
近年来的地震勘探表明，沉积物中甲烷水合物（MH）的存在对地震衰减有显著影响。我使用了日本中部近海东海南海海槽勘探井的垂直地震剖面（VSP）数据，以估计30-110 Hz地震频率下含MH沉积物的压缩衰减。使用两种不同的测量方法（频谱比和质心频移法）提供了一个机会，以验证衰减测量。还检查了衰减分析对不同深度间隔、钻孔不规则性和不同频率范围的敏感性，以验证衰减估计的稳定性。我发现在地震频率下，含MH的沉积物中没有明显的压缩衰减。从宏观上看，地震频率范围内衰减最高的峰对应于低饱和气层。相比之下，在声波频率范围（10-20 kHz）内的高压缩衰减区与相同井位置处甲烷水合物的存在有关。因此，这项研究表明，频率依赖性的衰减在MH轴承沉积物; MH轴承沉积物引起衰减的声波频率范围，而不是地震频率范围。作为一个可能的原因，为什么在30-110赫兹范围内的地震频率不受影响的MH轴承沉积物，我指出的MH轴承区薄层的效果。
Recent seismic surveys have shown that the presence of methane hydrate (MH) in sediments has significant influence on seismic attenuation. I have used vertical seismic profile (VSP) data from a Nankai Trough exploratory well, offshore Tokai in central Japan, to estimate compressional attenuation in MH-bearing sediments at seismic frequencies of 30–110 Hz. The use of two different measurement methods (spectral ratio and centroid frequency shift methods) provides an opportunity to validate the attenuation measurements. The sensitivity of attenuation analyses to different depth intervals, borehole irregularities, and different frequency ranges was also examined to validate the stability of attenuation estimation. I found no significant compressional attenuation in MH-bearing sediments at seismic frequencies. Macroscopically, the peaks of highest attenuation in the seismic frequency range correspond to low-saturation gas zones. In contrast, high compressional attenuation zones in the sonic frequency range (10–20 kHz) are associated with the presence of methane hydrates at the same well locations. Thus, this study demonstrated the frequency-dependence of attenuation in MH-bearing sediments; MH-bearing sediments cause attenuation in the sonic frequency range rather than the seismic frequency range. As a possible reason why seismic frequencies in the 30–110 Hz range were not affected in MH-bearing sediments, I point out the effect of thin layering of MH-bearing zones.
使用 Q 与偏移量方法估算含甲烷水合物沉积物的衰减
DOI：
--
发表时间：
2010
期刊：
影响因子：
--
作者：
Lee;K.;Matsushima;J.
通讯作者：
J.