水动力对煤层甲烷碳同位素的影响

通过对全国主要煤层气盆地水文地质条件、煤层气含量分布、煤层气地球化学特征进行全面的研究，结果发现在平面和剖面上，煤系水动力条件强的地区，不仅煤的含气量相对较低，煤层气甲烷碳同位素变轻的程度也较大；相反水动力较弱的地区或滞流水区，煤层气的含量相对较高，甲烷碳同位素变轻的程度也相对较小。在煤级相似的煤层中，煤层气的含量与甲烷碳同位素有较大的相关性，煤层含气量含越低，甲烷碳同位素就越轻。据此提出，流动的地下水是煤层甲烷碳同位素变轻的根本原因。

HYDRODYNAMIC INFLUENCE ON CARBON ISOTOPE OF COALBED METHANE

In order to clear the relationship between hydrodynamic conditions and carbon isotope, coalbed gas content, the hydrogeological conditions, coalbed gas content distribution, coalbed gas geochemical characteristics of the main coalbed gas basins in China are comprehensively researched in this paper. The result shows: both horizontally and vertically, the areas with stronger hydrodynamics, not only the gas content is low, but also the degree lightening of methane carbon isotope is higher; however, in the areas with weaker hydrodynamics, the coal usually has high gas content and the degree lightening of methane carbon isotope is also low. In the coalbeds with similar ranks, the gas contents have good correlation with δ13C1 values. The lower gas content is, the lighter carbon isotope value is. According to the phenomena above, it is put forward that the flowing groundwater is the key of causing the coalbed methane carbon isotope become lighter. (Financed by the National Basic Research Program project, No. 2002CB211705)