运聚体系—天然气水合物不均匀性分布的关键控制因素初探

海域天然气水合物的聚集和分布呈现出明显的不均匀性。本文运用“天然气水合物油气系统”的理论和方法，从墨西哥湾、布莱克海台、水合物脊、南海海槽等国际典型水合物赋存区的稳定条件、气体组分和来源、流体运移、沉积条件四个方面解剖各区水合物的成藏控制因素。通过分析和对比认识到水合物赋存区的范围相对较小，海底温度和压力可视为均一条件，热成因气和生物成因气均可作为水合物的气体来源，同一个区域内的气体组分相对稳定，但有利沉积体和为含气流体运移提供通道的运移条件，也即“天然气水合物运聚体系”是控制水合物分布的关键因素。南海北部陆坡神狐海域水合物储集于颗粒相对较粗、孔隙空间相对较大沉积体中，而下部的气烟囱和断层构成了神狐海域的含气流体运移通道，这种有利的运聚体系有机结合可能是天然气水合物富集的关键因素。因此，针对水合物储集体的精细沉积学解释和流体运移通道的解剖，可能是南海北部陆坡天然气水合物勘探中需要引起重视的一个方向。

Migration and Accumulation System: The Key Control Factors of Heterogeneous Distribution of Gas Hydrate

The accumulation and distribution of marine gas hydrate is obviously heterogeneous. Using the theory and method of “hydrate petroleum system”, we chose typical international hydrate occurrence area, such as Gulf of Mexico, Blake Plateau, Hydrate Ridge and Nankai Trough, to describe the hydrate distribution characteristic in detail, and analyze the accumulation control factors of hydrate from stable condition, gas composition and source, fluid migration and sediment condition of these areas. Through analysis and comparison of the typical case studies, the control actions of various factors on hydrate heterogeneous distribution were summarized systematically, and “gas hydrate migration and accumulation system” was proposed. The result indicates that the area of hydrate occurrence is relatively small, seafloor temperature and pressure are uniform, both thermogenic methane and biogenic methane can be the source gas, and the gas composition in the areas is similar. Therefore, the migration condition providing pathway for gas-bearing fluid move and the favorable sediment body providing potential space for hydrate accumulation are the key control factors of hydrate distribution. The theory of “hydrate migration and accumulation system” was applied to Shenhu area in northern continental slope of the South China Sea, the fluid migration condition and favorable sediment body were researched, and the hydrate migration and accumulation system in Shenhu area was discussed preliminarily. This study suggests that the analysis of fluid migration pathways and the sedimentological interpretation of hydrate reservoir are the important direction for hydrate exploration in northern continental slope of the South China Sea in the future.