松辽盆地徐家围子断陷无机成因天然气及其成藏模式

通过对徐家围子地区天然气组分、同位素资料以及气体包裹体资料的综合分析认为 ,该地区存在无机成因天然气。烃类气体中具有重碳同位素异常 ( >- 2 0‰ )和负碳同位素系列(δ13C1>δ13C2 >δ13C3)的同位素分布特征 ,表现出无机成因烃类气体的特点。高含量的无机CO2 气体和幔源氦的发现 ,指示着该区无机成因天然气主要来自于地球的深部。地幔热柱上升在地壳不同圈层中引起的岩浆火山活动是无机天然气的主要来源 ,而由此形成的地壳“网状”结构和基底大断裂是无机气上升运移至浅部聚集成藏的主要运移通道。构造活动间歇期和活动期分别以渗流方式和幕式涌流方式向上运移可能是深部流体运移的两种主要方式。古隆起带、岩浆侵入带以及基底大断裂带是无机成因天然气的有利聚集带。

ABIOGENIC NATURAL GASES AND THEIR ACCUMULATION MODEL IN XUJIAWEIZI AREA,SONGLIAO BASIN,NORTHEAST CHINA

On the basis of analysising chemical composition, carbon isotopes of natural gases and inclusions in volcanic rock, the authors discover that abiogenic natural gases exist in Xujiaweizi area. The abnormal of carbon isotopes(>-20‰) and the reverse of carbon isotopic series( δ 13 C 1> δ 13 C 2> δ 13 C 3) show a characteristic of abiogenic hydrocarbon gases. The appearance of high content CO 2 and the mantle derived 3He explains that inorganic gases mainly come from the deep earth. The activity of magma and volcanism in the crust caused by plume is the origin of abiogenic natural gases, and the net structure, big fault developed in the crust are their mainly migration path. Two patterns of gas migration are maybe slow seep out and episodic gush. Palaeohigh, magma intrusion belt and basement fault belt are favorable areas of abiogenic gases accumulation.