含瓦斯煤气固耦合作用在顺层双钻孔瓦斯抽采中的应用

Application of gas-solid coupling effect in the gas drainage with double boreholes along coal seam

为研究顺层双钻孔抽采过程中煤层瓦斯压力和渗透率的变化规律,将煤体视为双重孔隙结构介质,结合气体滑脱效应等因素的影响,建立了基于双孔结构特征的含瓦斯煤气固耦合作用模型,并通过有限元方法进行了数值解算分析。结果发现,瓦斯抽采时,两钻孔之间区域的瓦斯压力下降幅度明显大于其他区域,而在两钻孔区域的外侧至研究区域的边界处均出现了较为显著的瓦斯压力梯度;当钻孔间距为5 m和10 m时,同等条件下相较于钻孔间距为2 m和15 m的情况,煤层渗透率相对较大,而且瓦斯抽采有效区域分布更为均匀。同时,当钻孔间距小于5 m时,有效的瓦斯抽采影响区域会出现严重重叠现象,增加施工成本,而当钻孔间距大于10 m时,煤层中会产生一定程度的瓦斯抽采盲区,因此,5~10 m可以作为瓦斯抽采钻孔的合理布置间距。

In order to study the variation of gas pressure and coal permeability in the process of the gas drainage with double boreholes along coal seam,coals were considered as a dual-porosity medium and a gas-solid coupling model of coals containing gas based on the dual-porosity structural characteristics was established in light of the Klinkenberg effects.Then,the model was solved by using a finite element method.The results indicate that during the gas drainage process,the decrease magnitude of the gas pressure in the area between the two boreholes is obviously larger than the other areas,and a relatively significant gas pressure gradient appeared from the outside of boreholes to the boundary of study areas.When the borehole spacing is 5 m and 10 m,the coal permeability is relatively large and the effective area of gas drainage is distributed more evenly than that at the borehole spacing of 2 m and 15 m under the same conditions.In addition,when the borehole spacing is less than 5 m,the effective area arising from the gas drainage will overlap seriously and increase the construction cost caused by the too small borehole,and when the borehole spacing is larger than 10 m,the blind area of gas drainage caused by the excessive borehole spacing will occur.Therefore,5~10 m can be recognized as the reasonable borehole spacing of the gas drainage.