An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru
An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru
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DOI：
10.1306/0c9b288f-1710-11d7-8645000102c1865d
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发表时间：
1991-05
期刊：
影响因子：
3.5
通讯作者：
John J. Miller;M. Lee;R. Huene
中科院分区：
文献类型：
--
作者：
John J. Miller;M. Lee;R. Huene
在秘鲁近海ODP688站附近记录的地震反射数据显示，在与天然气水合物稳定场理论基础相对应的深度上有一个持久的似海底反射层(BSR)。尽管在太平洋和大西洋的科学钻探都在岩心中发现了天然气水合物，但通常避免在出现BSR的地区钻探，因为人们认为存在释放困在水合物沉积物下的游离气体的风险。为了进行BSR的定量分析，对地震数据进行了特征反褶积和真振幅恢复技术的再处理。利用从地震数据中提取的声学参数和688钻孔测量的物理性质创建的合成地震记录与观测的地震数据进行比较，以估计自由气带的厚度。结果表明，BSR在横向上是不连续的。在BSR波幅较高的地方，水合物沉积物下面5.5-17m厚的游离气提供了观察到的波形；在BSR波幅较低的地方，游离气带比5.5m薄得多或完全没有。
Seismic reflection data recorded near ODP Site 688, offshore Peru, exhibit a persistent bottom-simulating reflector (BSR) from a depth corresponding to the theoretical base of the gas hydrate stability field. Although gas hydrate has been recovered in cores from scientific drilling in both the Pacific and the Atlantic, drilling in areas exhibiting a BSR has usually been avoided because of the perceived risk of releasing free gas trapped beneath the hydrated sediments. To carry out a quantitative analysis of the BSR, the seismic data were reprocessed using signature deconvolution and true amplitude recovery techniques. Synthetic seismograms that were created using acoustic parameters extracted from the seismic data and physical properties from Site 688 borehole measurement were compared to the observed seismic data to estimate the thickness of the free-gas zone. Results indicate the BSR is discontinuous laterally. Where the BSR is of high amplitude, free gas in a zone 5.5-17 m thick beneath the hydrated sediments provides the observed waveform; where the BSR amplitude is low, the free-gas zone is much thinner than 5.5 m or is entirely absent.