南海潜在天然气水合物藏的成因及形成模式初探

文章分析了南海部分地区浅表层沉积物酸脱氢烃类气体的组成及ODP184航次部分岩屑样品罐顶气的组成与同位素特征,总结了南海部分气苗的烃类气体与同位素组成特征,并根据它们的同位素值估算了这些气体源的深度。估算值与实际值较吻合。在此基础上对这些烃类气体的成因进行了判别,结果为：北部陆坡的烃类主要来源于深部的裂解气,可能还有浅部生物气的混合,南部陆坡的烃类主要以浅部的生物气为主,还有热解气的混合。文中还对南海潜在天然气水合物藏的形成模式进行了初步的探讨。这些认识将有助于对南海天然气水合物的形成过程及同一构造背景下油气藏的关系的理解,对今后的普查勘探具有一定的意义。

Preliminary Discussion on Origin and Formation of Potential Gas Hydrates in South China Sea

Geochemical and isotopic compositions of some gas samples from the sub_surface sediments and from ODP Leg 184 in the South China Sea, determined by acid degassing and by depressurizing respectively, are dealt with in this paper. According to the isotopic analyses combined with the previous data, the authors calculated the source depth of the gases, which proves to be basically accordant with the real one. The gas origins were also determined. It is shown that the gases in the north are mainly thermolytical, mixed partly with biodegraded ones, whereas those in the south are mainly biodegraded, mixed partly with thermolytical ones. On such a basis, the formation model of the potential gas hydrates is established in the South China Sea. The results will help to understand the relationship between the gas hydrates and the oil reserves, and are of some significance to further exploration of the gas hydrates.