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水文地质条件对煤层气的赋存影响很大,在地下水动力条件强的地区煤的含气量比较低；地下水相对滞流的地区,煤层气含量较高．显然,流动的地下水对煤层气的保存不利．但在地下水带走煤层甲烷的机理上,研究得比较薄弱．根据流动的地下水不仅使煤的含气量降低,同时也导致了煤层甲烷碳同位素的分馏作用,使煤层甲烷的碳同位素值大幅度变轻的现象,提出流动的地下水带走煤层甲烷的方式主要是通过水对甲烷的溶解作用,然后被地下水带走,而并非是通常认为的水驱作用,也并非是煤层甲烷通过盖层的扩散作用导致强水动力条件地区煤层气含量降低．只有水溶作用才能使煤层气甲烷的碳同位素发生分馏作用且使煤层气中的甲烷碳同位素变轻,是流动地下水带走甲烷的有效途径,破坏煤层的含气性．
The hydrogeological conditions have a great influence on the occurrence of coalbed methane, and the gas content of coal is relatively low in regions with strong groundwater dynamic conditions. In areas where stagnation of groundwater is relatively stagnant, the CBM content is relatively high. Obviously, flowing groundwater is not good for CBM conservation. However, the study on the mechanism of groundwater removing coalbed methane is relatively weak. According to the flowing groundwater, not only the gas content of coal is reduced, but also the fractionation of carbon isotopes of methane in the coal seam is caused, and the carbon isotope value of methane in coal seam is drastically reduced. The water is not dissolved by the dissolution of methane and then by the groundwater. It is not the water flooding usually considered, nor is the coalbed methane content reduced due to the strong diffusion of methane through the caprock. Only the water-soluble effect can fractionate the carbon isotopes of methane in coalbed methane and make the carbon isotopes of methane in the coalbed methane lighter, which is an effective way to remove methane from flowing groundwater and destroy the gas-bearing property of coal seams.