南祁连盆地木里坳陷石炭系—侏罗系天然气水合物潜在气源岩地质特征

通过对南祁连盆地木里坳陷石炭系、二叠系、三叠系、侏罗系等4套层系5条剖面的野外测量及室内地质分析，明确了该区天然气水合物潜在气源岩的岩性特征、沉积相类型及沉积演化过程。石炭系—二叠系整体以出露中厚层砂岩夹薄层泥岩为主要特征，沉积浅海陆棚相、滨岸相和三角洲相，由于断层发育致使局部地层厚度减薄且泥质岩大部分缺失，可能难以成为天然气水合物潜在气源岩；上三叠统整体以发育中薄层泥岩与中薄至中厚层砂岩互层为主要特征，沉积相类型为潮坪相、湖泊相和河流相，泥岩累积厚度较大，是天然气水合物主要潜在气源岩；中侏罗统整体上以发育厚层泥岩、砂岩为主要特征，沉积相类型为辫状河相、三角洲相和湖泊相，是天然气水合物次要的潜在气源岩。研究结果为南祁连盆地木里坳陷天然气水合物气源岩研究提供了重要地质依据。

Geological Characteristics of Carboniferous Jurassic Potential Source Rocks for Natural Gas Hydrates in Muli Depression,South Qilian Basin

Through field geological survey and lab based analyses on the Carboniferous to Jurassic sedimentary sequences along five geological sections in the Muli depression of south Qilian basin, we clarify the regional lithological characteristics, sedimentary facies and sedimentary evolution. The Carboniferous Permian sedimentation system is characterized by medium thick sandstone with thin mudstone interbeds, and comprises shallow marine continental shelf, littoral and delta facies. The fault development likely reduced the partial strata thickness and the mudstone sequence is mostly lost, making it an unlikely potential source rock of gas hydrates. The Upper Triassic sedimentation system is characterized by the development of medium thick sandstone with medium thin mudstone interbeds, and comprises tidal flat, lacustrine and fluvial facies. The mudstone sequence is thick, making it the main potential source rock of gas hydrates. The Middle Jurassic sedimentation system is mainly characterized by thick mudstone with sandstone, and comprises braided river, delta and lacustrine facies, making it a potential source rock of gas hydrates. Our finding provides important implications on gas hydrate source rocks in the Muli depression.