Acoustic imaging of gas hydrate and free gas at the Storegga Slide
Acoustic imaging of gas hydrate and free gas at the Storegga Slide
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DOI：
10.1029/2003jb002863
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发表时间：
2004-04
影响因子：
--
通讯作者：
S. Bünz;J. Mienert
中科院分区：
文献类型：
--
作者：
S. Bünz;J. Mienert
[1]海底电缆（OBC）数据集的P波速度的分析表明，天然气水合物和游离气的存在北方侧翼的Storegga幻灯片。天然气水合物和游离气的分布和浓度在OBC的长度上表现出显着的变化。以水合物为沉积框架成分，采用有效介质理论模拟，孔隙空间中天然气水合物平均饱和度为5%。假设气体均匀分布，平均含气饱和度为0.45%。模拟海底反射层（BSR）通常被认为是增强反射的终止，但在某些地方表现为反射本身。与BSR有关的振幅异常主要是由天然气而不是水合物引起的。Storegga Slide的天然气水合物是由富气流体从下面的沉积物迁移到天然气水合物稳定带（GHSZ）而形成的。多边形断层的发育及与之相关的地层水的排出可能是该区流体流动的驱动力。沉积物的物理和地质性质控制着天然气的分布和富集，天然气主要沿沿着地层运移，而不是沿着基底运移。这种运移机制控制了富气流体进入水合物稳定带的流量，从而控制了水合物的分布和浓度的变化。
[1] Analysis of P wave velocities of an ocean-bottom cable (OBC) data set demonstrates the existence of gas hydrates and free gas on the northern flank of the Storegga Slide. The distribution and concentration of gas hydrates and free gas show significant variation over the length of the OBC. Average gas hydrate saturation of pore space is 5%, when modeled by effective-medium theory with hydrates as a sediment-frame component. Average gas saturation is 0.45% assuming homogeneous distribution. The bottom-simulating reflector (BSR) is generally identified as termination of enhanced reflection but in some places appears as a reflection proper. Amplitude anomalies related to the BSR are primarily caused by the gas and not the hydrates. The gas hydrates at the Storegga Slide develop from gas-rich fluids migrating into the gas-hydrate stability zone (GHSZ) from the sediments below. Development of polygonal faults and the related expulsion of formation water might drive the fluid flow in the area. The physical and geological properties of the sediments control the distribution and concentration of gas, which migrates predominantly along strata rather than along the base of the GHSZ. This migration mechanism controls the flux of gas-rich fluids into the GHSZ and hence the distribution of gas hydrates and the variation in gas hydrate concentration.