海底水合物冰丘的特征及意义

海底水合物冰丘是一种特殊的海底构造，外观表现从平滑浑圆的陡峭丘状体变化到粗糙不平的缓斜丘状体。地震剖面上，内部常表现为空白反射，并与似海底反射(BSR)紧密相关。归纳了前人对海底水合物冰丘的研究。综合分析认为规模较大的海底水合物冰丘通常形成于高通量汇聚型流体运移通道附近；海底水合物冰丘的出现可能指示了下部水合物及油气藏的赋存和大陆边缘汇聚型流体的运移；同时，在汇聚型流体运移条件下，伴随着流体向上运移的深部热流和高盐度水可能导致BSR深度变浅；此外，水合物冰丘的形成与发育为动态过程，其形成过程可分为水合物成核、聚集/冰丘型以及分解/冰丘垮塌3个阶段。开放型流动系统中形成的水合物丘的气体来源于“深部”沉积物渗滤的外部流体，可形成规模较大、高饱和度的水合物矿产，具有勘探价值。为更好地认识海底水合物冰丘演化史以及其与汇聚型运移通道、BSR分布位置等之间的关系，需要进一步开展海底调查、高精度多道地震调查，并结合地球化学等方法进行综合评价研究。

THE CHARACTERISTICS AND IMPLICATIONS OF SUBMARINE HYDRATE PINGO

Submarine hydrate pingo is a special kind of seabed topographic features, whose appearances vary from smooth, well-rounded, steep-sided mounds to rough, uneven, gently dipping mounds. Submarine hydrate pingo usually emerges as blank reflection in seismic profiles, and is closely related with bottom-simulating reflection (BSR). This paper summarizes the previous researches on the submarine hydrate pingo. On this basis, we believe that, the relatively large-scale submarine hydrate pingo is usually formed adjacent to high-flux focused fluid migration pathway; the occurrence of submarine hydrate pingo possibly indicates the occurrence of hydrate and hydrocarbon reservoir under the pingo, and the continental margin focused-fluid migration. At the same time, in the function of focused-fluid migration, upward migration of heat flow and highly saline fluids may result in the shoaling of BSR. Furthermore, the formation and evolution of submarine hydrate pingo is a dynamic process, conducted in an open flow system, which is divided into three phases, including hydrate nucleation, hydrate aggregation/pingo formation, and hydrate dissociation/pingo collapse. The gases of hydrate pingo formed in the open flow system are derived from external fluid after "deep" sediment percolation, which can form hydrate deposits with larger-scale and high saturation, and have the exploration value. To better understand the evolution history of submarine hydrate pingo, and the relationship between submarine hydrate pingo and focused migration pathway as well as the location of BSR distribution, more seabed survey and high-resolution multi-channel seismic survey should be carried out, and a comprehensive evaluation should be conducted combined with geochemical methods.