Abstract:

Marginal basins in the northern area of South China Sea have abundant natural gas resources. Not only a large amount of oilfield have been found in the shallow water of the northern area, but also great exploration breakthroughs of deepwater oil and gas have been made in the deep water of the southern area so far. A large number of biogenetic gas, sub-biogenetic gas and gas hydrate have been discovered in submarine and shallow layers of the deep water area. This paper, based on a large number of geochemical data of natural gas which received from gas exploration in recent years, as well as combining hydrocarbon accumulation geological conditions, makes a depth analysis and elucidation of the geological and geochemical characteristics of biogenetic gas and sub-biogenetic gas and the distribution feature of hydrocarbon source rocks in Neogene and Quaternary of Pearl River Mouth Basin in the northeast of South China Sea. On this basis, we preliminarily predict and estimate the generation amount and resource extent of biogenetic gas in Pearl River Mouth Basin. At the same time, by geochemical and geological analysis on the genetic type of gas hydrate at the deep water area in Baiyun sag in the southern area of Pearl River Mouth Basin, we further confirm that the gas hydrate discovered so far belongs to self-source diffusion model and biogenic mineralization hydrates type ,whose gas source is a kind of mixture dominated by biogenetic gas coming from original place and nearby, while the mineralization and accumulation model of gas hydrate can be classified into near-source migrated and accumulated model of self-generation and self-reservoir, which has tremendous resource potential.

Key words: Pearl River Mouth Basin, biogenetic gas and sub-biogenetic gas, self-generation and self-reservoir, genetic type of gas hydrate, gas hydrate accumulation mode