受载煤自发渗吸过程水分运移规律及其影响机理

Law of water migration during spontaneous imbibition in loaded coal and its influence mechanism

煤层注水所引入水分的渗透过程迫使煤层内原有裂隙相互沟通或形成新的裂隙网,为水在煤层内的流动提供网络通道。自发渗吸过程水与瓦斯发生相互作用,渗吸过程是一个有效的润湿过程,润湿效果与水分运移距离紧密相关。为揭示受载煤自发渗吸过程水分运移的影响机理,采用自主研发的“受载煤自发渗吸过程水分运移距离测试系统”,开展了受载煤自发渗吸实验。研究结果表明:水分侵入煤体后,水分与煤成为一个体系,煤样的电阻率发生突变、快变及渐变;等压渗吸过程中,受载应力越大,多分支毛细管束模型中的竖向毛细管平均孔径越小,水分运移距离越大;等压渗吸过程中,同一受载应力条件下,含瓦斯煤自发渗吸过程中水分的运移距离大于不含瓦斯煤自发渗吸过程中水分的运移距离;一端开放的毛细管、两端开放且从两端同时渗吸的毛细管在渗吸过程中均存在封堵效应;一端开放的毛细管渗吸过程中,毛细管周围的气体压力越大,封堵效应越明显;等压渗吸过程中,吸附平衡压力越小,多分支毛细管束模型中的水平毛细管吸水长度越长,多分支毛细管束模型中的竖向毛细管水分运移速率越慢,水分对微小孔的润湿效果越好。

The permeation process of water introduced by coal seam water injection forces the original fractures in the coal seam to communicate with each other or form a new fracture network,which provides a network channel for the flow of water in the coal seam.Water and gas interact with each other in the process of spontaneous imbibition.The imbibition process is an effective wetting process,and the wetting effect is closely related to the water transport distance.To reveal the influence mechanism of water transport in the process of spontaneous imbibition of loaded coal,the self-developed water transport distance test system during spontaneous imbibition in the loaded coal is used to carry out the experiment of spontaneous imbibition in the loaded coal.The results show that water and coal become a system after water intrudes into the coal.The resistivity of coal sample changes suddenly,rapidly and gradually.In the process of isobaric imbibition,the greater the loading stress,the smaller the average pore diameter of the vertical capillary in the multi-branch capillary bundle model,and the greater the water transport distance.The water transport distance in loaded gas-bearing coal is greater than that in the loaded non gas-bearing coal during the isobaric imbibition under the same loading stress.The capillary tube closed at one end and the capillary tube open at both ends with simultaneously spontaneous from both ends have a plugging effect.In the process of capillary imbibition with one end open,the greater the gas pressure around the capillary,the more obvious the plugging effect.In the process of isobaric imbibition,the smaller the adsorption equilibrium pressure is,the longer the liquid adsorption length of the horizontal capillary in the multi-branch capillary bundle model is.Also,the slower the water transport rate of the vertical capillary in the multi-branch capillary bundle model is,the better the wetting effect of water on the micro pores is.The research results provide a theoretical guidance for clarifying the wetting mechanism of gas-bearing coal in the spontaneous imbibition process of coal seam water injection.