祁连山冻土区烃源岩芳烃地球化学特征

Aromatic Geochemical Characteristics of Potential Source Rocks of the Wuli Premofrost in the Qilian Mountain Permafrost,China

为查明祁连山冻土区天然气水合物气源,在对该区可能烃源岩芳烃GC-MS分析的基础上,剖析了煤和泥岩的有机质来源、热演化程度和沉积环境。结果表明,研究区所有烃源岩样品中均检测到苯并蒽等陆源高等植物来源的芳烃化合物,且石炭系和侏罗系煤样1,2,5-TMN/1,3,6-TMN比值较高,分别为2.35和4.89,其余烃源岩样品该比值较低,为0.04~0.77,说明石炭系和侏罗系煤样陆源高等植物贡献较大,其余烃源岩样品则以低等水生生物输入为主;侏罗系(D-17)煤样F1和F2值分别为0.40和0.21,处于成熟阶段,其余烃源岩为高成熟烃源岩;侏罗系和二叠系煤样氧芴相对含量较高,分别为69.39%和40.92%,表征发育于氧化性环境,其余烃源岩氧芴含量较低,介于2.53%~13.43%之间,为还原性环境沉积的烃源岩。

In order to investigate the gas source of gas hydrate,on the basis of the GC-MS analysis of aromatic hydrocarbon of potential source rocks,a study on organic sources,depositional environment and the thermal evolution degree was carried out on the mudstones and coals from Carboniferous to Jurassic in Qilian Mountain permafrost.The results reveal that benzanthracene aromatic compounds originated from terrestrial higher plants were detected in the potential source rocks of this area,the ratios of 1,2,5-TMN/1,3,6-TMN of Carboniferous and Jurassic coal samples are high,2.35 and 4.89,respectively,and the ratios of other source rock samples are low,from0.04 to 0.77,which indicated that a larger contribution of terrigenous higher plants to Carboniferous and Jurassic coal samples,and the lower hydrobiont input predominates in organic matter of the rest samples;Jurassic coal sample（D-17） is in the mature stage with F1 and F2values of 0.40 and 0.21,respectively,and the other source rocks are high-mature source rocks;a relatively high concentrations of dibenzofuran（69.39% and 40.92%） reveal that the Permian and the Jurassic coal samples were developed in a oxidizing environment,and the dibenzofuran contents in the rest of samples are low,between 2.53% and 13.43%,suggested a reducing depositional environment of source rocks.