海底天然气水合物分解与甲烷归宿研究进展

综述了近年来天然气水合物分解与甲烷归宿等方面的研究成果。天然气水合物的汇聚与地质构造或地层圈闭有关，其溶解受物质转换控制，分解则受热转换控制。水合物释放甲烷的运移方式包括分散式、中心式和大规模排放式。缺氧氧化和耗氧氧化是甲烷在海洋环境中的2种主要转化方式。天然气水合物释放甲烷的最终归宿主要为：①重新形成天然气水合物；②形成化能自养生物群落和沉淀出碳酸盐沉积；③与氧发生氧化后转变为CO2；④直接排放进入到大气中。沉积物中的微构造、化能自养生物群落、自生碳酸盐矿物及其碳氧同位素组成是水合物释放事件的指纹记录。

Advances in Gas Hydrate Dissociation and Fate of Methane in Marine Sediment

Here we introduce and outline some advances of gas hydrate dissociation and fate of methane in marine sediment.A gas hydrate accumulation in sediments is related to a geological structure and/or stratigraphic trap,and the kinetic control for gas hydrate dissolution is mass transfer and that of dissociation is heat transfer.There are three main release types of methane release from gas hydrates within the accretionary sediment,such as distributed migration,focused migration and massive methane release.There now exists compelling evidence that anaerobic oxidation and aerobic oxidation of methane are two main reaction pathways in marine sediments and waters.Methane release by hydrate destabilization has been proposed to have four ultimate sinks,namely reformation gas hydrate,precipitation of carbonate minerals and formation of unique clam or tubeworm communities,transformation carbon dioxide,discharge into the atmosphere.The evidence preserved in the fossil sedimentary deposits,including sedimentary mictrostructures,nodular or encrusting diagenetic carbonates,specific benthic fauna and oxygen and carbon isotopic compositions of carbonates,might have registered the past occurrence of gas hydrates.