Distributions of gas hydrate and free gas accumulations associated with upward fluid flow in the Sanriku-Oki forearc basin, northeast Japan
Distributions of gas hydrate and free gas accumulations associated with upward fluid flow in the Sanriku-Oki forearc basin, northeast Japan
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DOI：
10.1016/j.marpetgeo.2020.104305
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发表时间：
2020-06
影响因子：
4.2
通讯作者：
Kakda Kret;T. Tsuji;Chanmaly Chhun;O. Takano
中科院分区：
文献类型：
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作者：
Kakda Kret;T. Tsuji;Chanmaly Chhun;O. Takano
我们对三维地震数据体进行了自动速度分析，得到了一个高分辨率的地震速度模型，并用该模型研究了日本东北部三陆-冲之弧前盆地流体行为对地下天然气分布的影响。通过它们之间的似海底反射(BSR)清晰的地震边界，我们将游离气聚集识别为从上覆高速天然气水合物中分离出来的低P波速度带。然后，我们使用传导模型从速度模型得出的BSR深度绘制出我们研究区域内向上的热流。估算的热流表明，向上的流体流量对天然气水合物和游离气的分布都有相当大的影响。高热流区(代表高流体流量)对应于下伏的渗透性地质特征，如气体烟囱、断层和多孔滑塌的边缘，表明这些特征提供了从始新世到渐新世源岩的流体运移途径，使天然气和水合物聚集在上覆沉积岩中。我们采用的技术有助于高分辨率绘制日本东部大陆边缘附近类似深水储集层和其他地区构造相似的板块俯冲边缘的天然气水合物和游离气聚集图。
We applied automated velocity analysis to a 3D seismic data volume to obtain a high-resolution seismic velocity model that we used to investigate the influence of fluid behavior on the subsurface distribution of gas in the Sanriku-Oki forearc basin, northeast Japan. We identified free gas accumulations as zones of low P-wave velocity separated from overlying high-velocity gas hydrates by the clear seismic boundary of the bottom-simulating reflection (BSR) between them. We then used conductive modeling to map upward heat flow in our study area from the depth of the BSR derived from the velocity model. The estimated heat flow demonstrates that upward fluid flux has considerable influences on the distributions of both gas hydrate and free gas. The areas of high heat flow (representing high fluid flux) correspond to underlying permeable geological features such as gas chimneys, faults, and the edges of porous slumps, suggesting that these features provide fluid migration pathways from Eocene to Oligocene source rocks to free gas and hydrate accumulations in overlying sedimentary rocks. The techniques we have employed can contribute to the high-resolution mapping of gas hydrate and free gas accumulations in similar deep-water reservoirs off the eastern continental margin of Japan and at tectonically similar plate subduction margins in other regions.