Geological controls on shallow gas distribution and seafloor seepage in an Arctic fjord of Spitsbergen, Norway
Geological controls on shallow gas distribution and seafloor seepage in an Arctic fjord of Spitsbergen, Norway
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挪威斯匹次卑尔根北极峡湾浅层天然气分布和海底渗漏的地质控制
DOI：
10.1016/j.marpetgeo.2019.05.021
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发表时间：
2019
影响因子：
4.2
通讯作者：
A. Braathen
中科院分区：
文献类型：
--
作者：
S. Roy;K. Senger;M. Hovland;M. Römer;A. Braathen
这项研究整合了高分辨率的浅层和深层地球物理数据集，以研究与影响斯匹次卑尔根岛中部Nordfjorden（挪威北极）流体流动的地下浅层天然气和地质特征有关的海底渗流系统。这是斯匹次卑尔根岛伊斯峡湾系统的支流峡湾之一，其麻点密度最高，可达20个/平方公里。在300 km 2的大面积研究区域中，人工识别出535个麻点，直径从10 m到212 m不等，深度从1 m到8 m不等。55公里新的高分辨率海底下声学数据记录的与海底下渗漏有关的声学特征，如反射增强、声学消隐和浑浊带，表明在凹坑之下的海洋沉积物中存在浅层气体（游离和/或溶解）。属于古近纪西斯匹次卑尔根褶皱-冲断带和早白垩世火成岩岩床的构造特征（逆冲断层和相关褶皱）已在三叠纪和二叠纪序列的二维多道地震数据上得到解释。其中一些断层和火成岩岩床形成了麻坑密度高的海底脊，它们通常是对齐的。在Nordfjorden南部的水柱中，在地下浅层天然气点和逆冲断层上方，对海底活跃气体渗漏造成的声闪进行了成像。这些地球物理数据集的综合分析表明，近海底构造变形地层在流体（液体和/或气体）的上倾传播，海洋沉积物中浅层天然气的分布和海底渗流中起着重要的作用。
This study integrates high-resolution shallow- and deep-geophysical datasets to study the seabed seepage systems linked to subsurface shallow gas and geological features influencing the fluid flow in Nordfjorden, central Spitsbergen (Arctic Norway). This is one of the tributary fjords of the Isfjorden fjord system in Spitsbergen which has the highest density of pockmarks ranging up to 20/km2. The 535 pockmarks identified manually in the 300 km2large study area have diameters ranging from 10 m to 212 m, and depth varying between 1 m and 8 m. Sub-surface seep-related acoustic features such as, enhanced reflections, acoustic blanking and turbidity zones recorded on 55 km of new high-resolution sub-bottom acoustic data suggest shallow gas (free and/or dissolved) occurrences in the marine sediments beneath the pockmarks. Structural features (thrust faults and associated folds) belonging to the Palaeogene West Spitsbergen fold-and-thrust belt and Early Cretaceous igneous sills have been interpreted on 2D multichannel seismic data, in the Triassic and Permian successions. Some of these faults and igneous sills form seafloor ridges, where pockmark density is high, and they are typically aligned. Acoustic flares attributed to active gas seepage from the seafloor were imaged in the water column in the southern part of Nordfjorden, above the sub-surface shallow gas occurrences and thrust faults. The integrated analysis of these geophysical datasets suggests that the near-seafloor tectonically deformed stratum plays an important role in the up-dip propagation of fluids (liquids and/or gas), distribution of shallow gas in marine sediments, and seepage at the seafloor.