塔里木盆地天然气中稀有气体地球化学特征

Geochemical characteristics of noble gases in natural gases from the Tarim Basin

何大祥 唐友军 胡锦杰 莫少武 陈践发

Daxiang He Youjun Tang Jinjie Hu Shaowu Mo Jianfa Chen

利用天然气中稀有气体同位素组成特征可以有效地判识天然气的成因和来源。塔里木盆地不同构造单元典型天然气藏天然气中稀有气体丰度和同位素组成分析表明，天然气样品的He/He值均普遍较低，/值均小于0.1，天然气中的稀有气体主要为壳源放射性成因，指示低温“冷盆”的特征。He/He组成与热流值和古地温梯度之间没有简单的对应关系，指示盆地地幔热的来源较少。库车坳陷天然气成藏时代较晚，多为喜马拉雅期，其Ne/Ne较低，反映其受地幔端元混染作用较小。天然气中Xe相对亏损，指示无明显的幔源挥发分的混入，受岩性及构造特征的影响，相较于塔北隆起、塔中隆起天然气，库车坳陷天然气中Xe的壳源特征更为明显。

The isotopic characteristics of noble gases have been long used in the study of the genesis and origin of natural gases.A systematic analysis of the abundance and isotopic composition of noble gases in natural gases from different structural units shows that the majority of samples is low in the ratio of He/He, with the values generally less than 0.1, indicating a crustal radiogenic genesis of the noble gases and a significant "cold" feature of the basin.No simple correlation exists between the He/He ratios and both of heat flow and paleo-geothermal gradient, revealing little heat sourcing from mantle.The lower level of Ne/Ne ratios influenced by the relatively late hydrocarbon generation and accumulation period, mostly during the Himalaya movement, shows an inconspicuous proportion of mantle-derived gas in natural gases from Kuqa Depression.The relative depletion of Xe shows that the mixing of mantle-derived volatile constituents is insignificant.Furthermore, compared with the natural gases from Tabei Uplift and Tazhong Uplift, the Xe in natural gases from Kuqa Depression was more likely derived from the crust due to the influences of lithology and structural features.

10.11743/ogg20200409