中国东部幔源CO气藏的CO/He比率及形成机制

CO/He RATIO OF MANTLE-DERIVED CO GAS POOLS AND ITS FORMATION MECHANISM IN EAST CHINA

许多 周瑶琪 朱岳年 查明

Xu Duo Zhou Yiaoqi Zhu Yuelian Cha Ming

我国东部含油气盆地幔源CO气藏的CO/He比率在10-10之间,与幔源气体脱离玄武岩浆时恒定的CO/He比率(2×10～7×10)相比较发生了很大的变化。其中形成于中生代的万金塔CO气藏,具有10～10的高CO/He比率,而新生代以来形成的黄骅、济阳、苏北、三水等地的幔源CO气藏,均以10-10的低CO/He比率为特征。研究表明,幔源气藏CO/He比率的形成受到了幔源气体的释放机制的控制。在玄武岩浆喷溢、侵入为幔源气藏的形成提供大量气源的同时,岩浆房中的幔源气体通过深切岩浆房的断裂通道直接释放,对幔源气藏的形成、幔源气体的补给以及气藏CO/He比率等地球化学特征的塑造具有重要作用。同时,我国东部含油气盆地中无机成因CO气藏的CO/He比率特征为气藏的幔源成因提供了新的证据。

CO/He ratio of the mantle-derived CO gas pools ranges from 10 to 10 in petroliferous basins in East China.This differs greatly from the constant CO/He ratio of 2?10-7?10 of the manile-derived CO gas while Separatng from the basalt magma. The CO/He ratio of Wanjingta CO gas pool formed in Mesozoic in Sogliao Basin ranges from 10-10, but that of the mantle-derived CO gas pools formed since Cenozoic in Huangha, Jiyang, Subei and Shanshui Basins is as low as 10-10. This indicates that CO/He ratio of the mande-derived gas pools is controlled by release mechanism of the gases.The eruption and intrusion of the basalt magma provided a large number of gas sources for the formation of the mantle-derired gas pools; the CO gas in the magma chamber would release directly along fault-passages which cut the chamber deeply. This played an important role in the formaion, the gas source supplies, the CO/He ratio and geochemical properties of the pools. Meantime, characters of CO/He ratio of the inomanic origin CO gas pools provide a new evidence for its mantle-derived origin.

10.11743/ogg19990404