Analytic techniques of the light hydrocarbon and the carbon isotope of natural gases were employed to cast light on the natural gas origin of shallow gas reservoirs and the migration characteristics, and the origin of the gas hydrate proved in the north of the South China Sea, in combination with the regional geology and gas hydrate data. The result indicates that the natural gas from shallow reservoirs is a mixture of biogenic gas and thermal genetic gas. It reveals that the potential gas source for gas hydrate was not limited to biogenic gas, but the biodegradation gas and thermal genetic gas have great contribution to the gas hydrate. The thermal genetic gas in the mixture gases is from deep hydrocarbon reservoirs, which indicates that the gas hydrate maybe has a close relationship with the regular deep hydrocarbon reservoirs. It can be concluded that two types of gas hydrates originated from biogenic gas and mixture gas exit in Shenhu deep zone of continental margin in the north of the South China Sea. The deep zone of Baiyun Sag in Pearl River Mouth basin will be the most valuable target for gas hydrate exploration in this area.%应用天然气浓缩轻烃分析技术、天然气碳同位素分析技术,结合现有地质资料和水合物分析资料,对南海北部浅层气的成因特征、运移特征及南海已发现的水合物成因特征进行了详细分析.研究结果表明,南海北部盆地浅层气藏普遍具有混合成因的特征,并主要以生物气-热成因气(生物降解气)混合气为主.浅层气的这种混合成因特征揭示了水合物的气源不仅与生物气有关,也与热成因气生物降解气有关,而混合气中的热成因气(生物降解气)的气源来自深部油气藏,表明水合物的气源与常规深部油气藏有密切的关系.南海北部大陆边缘神狐陆坡深水区天然气水合物主要为生物成因和混合成因二种类型,生物成因的水合物δ13C1值分布在-57‰～-74.3‰之间,混合成因的水合物δ13C1值分布在-46.2‰～-63‰之间.珠江口盆地白云凹陷深水区为南海北部水合物最具潜力的勘探区.
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