顺层瓦斯抽放钻孔渗流场数值模拟及应用

Numerical simulation and application of drilling gas drainage holes along seam in current seam

切实可行的瓦斯抽放方式是预防煤矿瓦斯事故灾害的重要方法之一。为了能准确合理地确定顺层瓦斯抽放钻孔的布置参数,基于煤层瓦斯流动理论,建立钻孔抽放瓦斯渗流场数学模型,运用有限元分析软件COMSOL-Multiphysics,以董家河煤矿22518工作面为例,对工作面顺层钻孔瓦斯抽放过程进行数值模拟,研究抽放钻孔周围瓦斯渗流场分布规律,确定22518工作面顺层瓦斯抽放钻孔的布置方式。结果表明：瓦斯抽放初期,瓦斯抽放量较大,持续时间较长,抽放瓦斯卸压作用使得钻孔周围一定范围内的煤体渗透率显著提高,在钻孔中心位置,瓦斯渗流速度达到最大值,煤体孔隙率随着抽放时间的推移逐渐降低,设计钻孔直径90 mm,抽放负压20 k Pa,钻孔有效抽放半径确定为3～4 m时抽放效果较好。该研究结果对提高瓦斯抽放效率,预防瓦斯事故灾害,保障煤矿安全生产具有重要的指导意义。

The feasible gas extraction method is one of the important approaches to prevent the occur- rence of the mine gas accident. In order to determine the reasonable parameters of drilling gas drainage holes along seam, based on gas flow theory, seepage field mathematical model of gas suction by drilling is established,by using the finite element analysis method of COMSOL-Muhiphysics, the process of gas drainage in drilling hole along seam in current seam is numerically simulated to study the distribution rules of gas permeation field around drainage hole in case of 22518 working face in Dongjiahe coal mine ,and determine the arrangement modes of drainage holes of drilling gas along seam in current seam. The study results show that, large amount and long duration of gas extraction content occurred at the beginni pressure of ng of gas drainage period, the coal permeability increases visibly under the action of relief gas extraction around the drill, seepage velocity reached maximum at the center of drill and the coal porosity decreases gradually with the time. In the conditions of drilling hole diameter of 90 mm and negative suction pressure of 29 kPa, the effective drainage radius is best set to 3 ～ 4 m. The results have important guiding significance for increasing the gas drainage efficiency, preventing mine from gas accident and guaranteeing coal mine safety production.