Widespread seafloor methane venting has been reported in many regions of the world oceans in the past decade. Identifying and quantifying where and how much methane is being released into the ocean remains a major challenge and a critical gap in assessing the global carbon budget and predicting future climate [C. Ruppel, J. D. Kessler. Rev. Geophys. 55, 126–168 (2017)]. Methane hydrate (CH4⋅5.75H2O) is an ice-like solid that forms from methane–water mixture under elevated-pressure and low-temperature conditions typical of the deep marine settings (>600-m depth), often referred to as the hydrate stability zone (HSZ). Wide-ranging field evidence indicates that methane seepage often coexists with hydrate-bearing sediments within the HSZ, suggesting that hydrate formation may play an important role during the gas-migration process. At a depth that is too shallow for hydrate formation, existing theories suggest that gas migration occurs via capillary invasion and/or initiation and propagation of fractures (Fig. 1). Within the HSZ, however, a theoretical mechanism that addresses the way in which hydrate formation participates in the gas-percolation process is missing. Here, we study, experimentally and computationally, the mechanics of gas percolation under hydrate-forming conditions. We uncover a phenomenon—crustal fingering—and demonstrate how it may control methane-gas migration in ocean sediments within the HSZ.

在过去十年中，世界海洋许多地区都报道了广泛的海底甲烷排放。在评估全球碳预算和预测未来气候的过程中，识别和量化甲烷向海洋中释放的位置和数量仍然是一个重大挑战，也是一个重大差距。Ruppel，JD Kessler。地理专家。55，126–168（2017）]。甲烷水合物（CH4⋅5.75H2Ø）是一种冰状固体，由甲烷-水混合物在深海环境（> 600 m深度）（通常称为水合物稳定区（HSZ））典型的高压和低温条件下形成。广泛的野外证据表明，高渗区中甲烷的渗漏经常与含水合物的沉积物共存，这表明水合物的形成在气体迁移过程中可能起重要作用。在对于水合物形成而言太深的深度，现有理论表明气体运移是通过毛细管侵入和/或裂缝的萌生和传播发生的（图1）。但是，在HSZ内部，缺少解决水合物形成参与气体渗透过程的理论机制。在这里，我们通过实验和计算研究 在水合物形成条件下的气体渗透机理。我们发现一种现象-地壳指法-并演示它如何控制HSZ内海洋沉积物中甲烷气体的迁移。