煤层钻孔瓦斯抽采有效半径影响因素分析

Analysis on influential factors of effective radius of gas extraction from coal seam borehole

为了揭示不同因素对煤层钻孔瓦斯抽采有效半径的影响,更准确地预测煤层瓦斯抽采有效半径,提高瓦斯抽采率,基于瓦斯在煤层中的运移、渗流与Klinkenberg效应等理论,构建了瓦斯抽采数学模型;采用COMSOL软件模拟了初始瓦斯压力、渗透率、抽采负压、孔径和抽采周期等5个因素对煤层瓦斯抽采有效半径的影响。结果表明:煤层瓦斯抽采有效半径与初始瓦斯压力的变化呈负相关关系,与渗透率、抽采负压、钻孔孔径和抽采周期的变化呈正相关关系。利用灰色关联数学模型,根据数值模拟结果对这5个影响因素进行主次顺序分析,得到初始瓦斯压力对瓦斯抽采有效半径的影响最强,渗透率次之,抽采负压的影响最弱。研究成果可为煤层瓦斯抽采工艺的井下施工提供理论依据。

In order to reveal the influence of different factors of effective radius of gas extraction from coal seam borehole,predict the effective radius of coal seam gas extraction more accurately and improve the gas extraction rate,this paper built a mathematical model of gas extraction based on the theories of gas migration,seepage and Klinkenberg effect in coal seam;COMSOL software was used to simulate the influence of five factors on the effective radius of coal seam gas extraction,including initial gas pressure,permeability,negative pressure of extraction,aperture and extraction cycle.The results show that the effective radius of coal seam gas extraction is negatively correlated with the change of initial gas pressure,and positively correlated with the change of permeability,negative pressure,borehole diameter and extraction cycle.The grey relational mathematical model is used to analyze the five influencing factors in primary and secondary order according to the numerical simulation results,it is found that the initial gas pressure has the strongest influence on the effective radius of gas extraction,followed by the permeability,and the negative pressure of gas extraction has the weakest influence.The research results can provide theoretical basis for underground construction of coal seam gas extraction technology.