沁水盆地南部煤层气藏的地球化学特征

GEOCHEMICAL CHARACTERISTICS OF CBM RESERVOIRS IN SOUTHERN QINSHUI BASIN

指出沁水盆地南部煤层气的地球化学特征是甲烷含量超过95%,1δ3C1值变化于-61.7‰^-28.7‰之间,而大部分甲烷的1δ3C1值偏轻,为-40‰^-30‰之间,太原组甲烷的1δ3C1则更轻。认为这主要是由于构造热事件及水动力条件综合作用的结果,构造热事件不仅促成二次生气,而且改善了煤储层物性,大大增强了CH4与CO2交换作用及甲烷的解吸—扩散—吸附的动态平衡过程,强烈的水动力条件也是导致煤层甲烷碳同位素变轻的重要原因,太原组甲烷碳同位素更轻主要是由于流动的地下水的溶解作用造成的。

The geochemical characteristics of the coalbed methane （CBM） in Qinshui show that the methane is over 95% and δ^13C1 is --61.7‰-28. 7‰, being mainly concentrated in - 40‰ - 30‰ , which are the result of high-over thermogene. The tectonic thermal evolution and hydrodynamic condition are the critical factors for δ^13C1 being light. The tectonic thermal evolution improved the reservoir physical properties, contributing to the exchange of CH4 and CO2. Moreover, the strong hydrodynamic condition.is another important factor of δ^13C1 being lighter.