摘要
通过开展南祁连盆地木里坳陷天然气水合物基础地质剖面调查工作，对石炭系、二叠系、三叠系、侏罗系共四套层系5条剖面的炭质泥岩、泥岩等样品进行了系统采样与分析，在此基础上深入研究四套层系的有机质丰度、有机质类型和有机质成熟度等地球化学特征，分析及对比各层系的有机地球化学指标，以探讨不同层系烃（气）源岩为天然气水合物提供的气源条件。结果表明：石炭系-二叠系有机质丰度偏低，（总有机碳含量）普遍小于0.4%，为非和差烃源岩，有机质类型主要为Ⅱ型和Ⅲ型，有机质成熟度为过成熟，生烃能力较差，难以成为天然气水合物潜在气源岩。三叠系样品值普遍大于1%，氯仿沥青“A”平均为0.89‰，以很好和好烃源岩为主，并含少量差和非烃源岩，有机质类型以Ⅲ型为主，含少量Ⅱ型，镜质体反射率值为0.74%~0.98%，整体上处于成熟阶段，生气能力较强，可作为天然气水合物主要潜在气源岩。侏罗系以很好、好和中等烃源岩为主，并含部分差烃源岩，有机质类型主要为Ⅱ型和Ⅲ型，值为0.62%~0.97%，整体上处于成熟阶段，可作为天然气水合物次要潜在气源岩。
Abstract
During the investigation of the basic geological profile of natural gas hydrates in the Muli Depression, Southern Qilian Basin, we analyzed the carbon-rich mudstone and mudstone sampled from 5 sections of the Carboniferous, Per-mian, Triassic and Jurassic sequences.The geochemical characteristics such as organic matter abundance, organic matter type and organic matter maturity of four sequences were accordingly studied in detail.The organic geochemical indexes of each sequence were analyzed and compared in order to explore the gas source rock qualities for different sequences of (gas) source rocks for natural gas hydrates.The results show that the Carboniferous-Permian organic matter abundance is relatively low, the (total organic carbon) content is generally less than 0.4%, both of which indicate the source rocks are very lean.The kerogen are mainly over-matured TypesⅡ and Ⅲ organic matters, resulting in poor hydrocarbon generation capacity.Thus, the source rocks could not be the potential gas source rocks for natural gas hydrate generation.The samples collected from the Triassic strata have value of generally greater than 1% and an average chloroform bitumen "A" of 0.89, which are mostly good and very good source rock samples, with a small number of samples with poor or non-hydrocarbon source rock quality.The organic materials are mainly matured Type Ⅲ as a whole with a small number of Type Ⅱ, with a vitrinite reflectance () value of 0.74%-0.98%.These strata can be viewed as the main potential gas source rocks for natural gas hydrate generation.The Jurassic strata are dominated by source rocks of very good, good, and medium qualities with limited number of poor source rocks.Their organic materials are mainly matured Type Ⅱ and Ⅲ with a value of 0.62%-0.97%, and thus can be regarded as the secondary potential gas source rocks for the generation of natural gas hydrates.
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