【摘要】 以海底为基准,将高分辨率多道地震反射数据分离为两个独立部分,并分别对水体和地层成像.水体的成像结果显示了两个明显形如羽状流的异常,与之对应地层的地震反射剖面显示在海底处出现海底下陷、气体溢出口等与甲烷渗漏相关的地形地貌特征,并在海底之下不足100m的深度位置出现一个指示天然气水合物存在的明显的似海底反射.详尽的速度分析发现,似海底反射和溢出口之下沉积地层的声波速度明显下降,并且地震反射特征也与地层含气有关.通过对所有信息综合分析,推测这些地球物理异常和特殊地形地貌特征(如羽状流、声波速度反转、溢出口、海底下陷、浅部BSR等)很可能是甲烷气体沿运移通道进入近海底沉积物中形成天然气水合物或溢出至海水中所致.研究结果表明,多道高分辨率地震反射数据具有探测渗漏型天然气水合物的能力.更多还原

【Abstract】 Taking the seafloor as datum, the high resolution seismic reflecting data acquired in Shenhu area are divided into two parts for the imaging of water column and strata respectively. Two apparent echoes shaped like plume show in the water column and the particular geomorphology such as vents and depressions of seafloor suggests the existence of the gas seepage occurred opposite them on the seismic reflecting section. Moreover, a classical bottom simulating reflector which indicates the presence of gas hydrates appears at the depth less than 100 m. The detailed velocity field reveals that acoustic velocity of sediments decreases beneath both the seep sites and bottom simulating reflector and the seismic reflecting characteristics seem to be related to the gas-bearing of strata. It can be concluded that geophysical anomalies (plumes, acoustic velocity reverse, BSR (bottom simulating reflector)) and the expressions of particular geomorphology of seabed (vents and depressions or craters) should have been resulted from the migration of free gas into the sediments of subsurface and then the formation of gas hydrates or the direct seepage into the seawater. This study indicates that high resolution multi-channel seismic reflecting data has great potential for characterizing the anomalies and then detecting the seepage gas hydrates reservoir.更多还原