南海北部珠江口盆地深水区天然气水合物成因类型及成矿成藏模式

南海北部大陆边缘珠江口盆地油气资源丰富，迄今为止不仅在北部浅水区勘探发现了大量油田，建成了超千万立方米的石油年产能区，而且在南部深水区亦 获得了深水油气勘探的重大突破；在深水海底浅层还发现了大量生物气/亚生物气显示，钻探获得了天然气水合物。根据近年来油气勘探及海洋地质勘查所获大量天然气资料，结合油气成藏地 质条件，深入分析了珠江口盆地生物气/亚生物气地质地球化学特征及其气源岩展布特点，初步预测和估算了其生物气生成量与资源量。通过珠江口盆地南部深水区白云凹陷(神狐调查区)天然 气水合物形成的地质地球化学条件分析，进一步证实了该区勘查发现的天然气水合物，主要属生物气成因类型，其气源供给主要来自原地近源以生物气为主的混合气，天然气水合物成矿成藏 模式则主要属于生物气源供给“自生自储型”近源富集成矿成藏类型，且资源潜力颇大。

Biogenetic and Sub-biogenetic Gas Resource and Genetic Types of Natural Gas Hydrates in Pearl River Mouth Basin,Northern Area of South China Sea

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.