煤层钻孔瓦斯抽采效果影响因素分析

Analysis of influencing factors on gas drainage effect of coal seam boreholes

为研究瓦斯抽采效率的影响因素,考虑吸附瓦斯与游离瓦斯建立了煤层瓦斯流动的流固耦合模型,本文采用COMSOl数值模拟软件,分析了不同初始地应力、初始渗透率以及钻孔直径条件下的瓦斯抽采效果以及抽采有效半径变化情况。研究结果表明:初始地应力、初始渗透率和钻孔直径均会影响瓦斯抽采效果,但其对瓦斯抽采效果的影响程度不同;抽采有效半径对初始渗透率的变化最敏感,钻孔直径次之,对初始地应力的敏感程度最低;在某一钻孔直径范围内,瓦斯抽采效果随钻孔直径的增加变化不明显,而超出此范围后,抽采效果有明显提高,选择合适的钻孔直径对于提高瓦斯抽采效果具有重要作用。

In order to reveal the influencing factors of gas drainage,a fluid-solid coupling model of coalbed methane considering the adsorbed and free gas is established in this paper.The COMSOL numerical simulation software is used to analyze the gas drainage effect and the variation of the effective radius of gas drainage under the conditions of different initial in-situ stress,initial permeability and borehole diameter.The research results show that the initial in-situ stress,initial permeability and borehole diameter will all affect the gas drainage effect,but they have different effects on the gas drainage effect.The effective radius of drainage is most sensitive to the change of initial permeability,followed by the borehole diameter and the initial in-situ stress.The gas drainage effect does not change significantly with the increase of the borehole diameter within a certain range.However,the gas drainage effect is significantly improved beyond this range.Therefore,selecting an appropriate borehole diameter is very important to improve the gas drainage effect.