华南陆缘中生界烃源岩条件评价

ASSESSMENT OF MESOZOIC SOURCE ROCKS AT THE MARGIN OF SOUTH CHINA CONTINENT

华南陆缘出露的上三叠统-白垩系,累计厚度超过10 000m,露头调查未见油苗,烃源岩主要为泥岩、碳质泥岩和煤线,有机质类型以Ⅱ-Ⅲ型为主。上三叠统小水组,发育较深水的海相、Ⅱ型良好烃源岩,TOC为1.17%～5.43%;下侏罗统桥源组发育海陆过渡环境的Ⅲ型良好烃源岩,TOC为1.36%～10.37%;下侏罗统其他层系(金鸡组、银瓶山组、上龙水组、长埔组、吉水门组)发育浅海-半深海相的中等-好的烃源岩,TOC为0.5%～1.76%。烃源岩均已处于成熟-过成熟阶段。小水组、蓝塘群烃源岩品质良好,厚度巨大,在南海北部海域开展中生界烃源岩研究时,值得重点关注是否有与之相当的烃源岩层系发育。

The total thickness of the Upper Triassic and Cretaceous are over 10000 meters around the mar- gin of South China continent. No oil seepage has been discovered so far on outcrops. The source rocks are mainly composed of mudstones, carbonaceous mudstones and coal seams. The organic matter is of type Ⅱ- Ⅲ. High quality source rocks, which contain 1.17%5.43% of TOC, have been found in the deep marine deposits of the Xiaoshui Formation of Upper Triassic. The Bianqiaoyuan Formation of Lower Jurassic is a transitional facies, where source rocks have been found with 1.36%-10.37% of TOC. In other Forma- tions of Lower Jurassic there are rocks of neritic -bathyal marine facies with 0.5%-1.76% of TOC. The source rocks are now matured or over matured. Among them, the source rocks in the Xiaoshui Formation and Lantang Group are the best with regard to the high TOC and big thickness. In addition to the Mesozo- ic source rocks in Northern South China Sea, the source rocks around the margin of South China must be taken into account.