The potential influence of shallow gas and gas hydrates on sea floor erosion of Rock Garden, an uplifted ridge offshore of New Zealand
The potential influence of shallow gas and gas hydrates on sea floor erosion of Rock Garden, an uplifted ridge offshore of New Zealand
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浅层天然气和天然气水合物对新西兰近海隆起海脊 Rock Garden 海底侵蚀的潜在影响
DOI：
10.1007/s00367-010-0186-y
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发表时间：
2010
影响因子：
2.1
通讯作者：
S. Henrys
中科院分区：
文献类型：
--
作者：
G. Crutchley;S. Geiger;I. Pecher;A. Gorman;Hai Zhu;S. Henrys
岩石花园山脊顶部的区域侵蚀，很可能与其天然气水合物系统有关。岩石花园山脊是新西兰希库兰吉俯冲边缘内的一个水深较高的地方。地震数据显示，部分气穴似乎被困在天然气水合物稳定性的浅层底部之下。在详细的二维地质模型上进行的稳态流体流动模拟表明，异常流体压力可以在海底附近形成，以响应渗透率较低的含水合物沉积物和下面的气穴。瞬变模拟表明，流体超压的大尺度循环可能发生在几年到几十年的时间尺度上。我们预测，由于更明显的超压产生和天然气通过含水合物的沉积物的运移，强烈的水力压裂区域将优先在山脊顶部下方而不是侧翼下方发育。研究结果表明，浅层天然气水合物体系的流体动力学作用可能是水压致裂对山脊顶沉积物的弱化和侵蚀的主要原因。
Regional erosion of the Rock Garden ridge top, a bathymetric high within New Zealand’s Hikurangi Subduction Margin, is likely associated with its gas hydrate system. Seismic data reveal gas pockets that appear partially trapped beneath the shallow base of gas hydrate stability. Steady-state fluid flow simulations, conducted on detailed two-dimensional geological models, reveal that anomalous fluid pressure can develop close to the sea floor in response to lower-permeability hydrate-bearing sediments and underlying gas pockets. Transient simulations indicate that large-scale cycling of fluid overpressure may occur on time scales of a few to tens of years. We predict intense regions of hydro-fracturing to preferentially develop beneath the ridge top rather than beneath the flanks, due to more pronounced overpressure generation and gas migration through hydrate-bearing sediments. Results suggest that sediment weakening and erosion of the ridge top by hydro-fracturing could be owed to fluid dynamics of the shallow gas hydrate system.