三维预设原生裂隙下的煤层低压注水数值模拟研究

Study of Numerical Simulation of Coal Seam Low-pressure Water Injection Based on Three-dimensional Precast Pre-existing Fractures

为研究煤层注水过程中,煤体内大量原生裂隙对水分运移过程及润湿效果的影响,采用COMSOL Multiphysics软件模拟注水过程中的渗流压力场、速度场与水分增量,并通过MATLAB编程建立煤体内大量三维原生裂隙的随机分布模型。研究结果表明:注水工作进行约60h后,煤体内各处水分渗流速度趋向一致且保持相对稳定;水分增量场与渗流压力场、渗流速度场在注水前期的分布基本一致;随着大量原生裂隙被水分浸润,裂隙在起到储水作用的同时,也加速了附近煤体的润湿速度;但可见若原生裂隙未与注水孔相交连通,其加快煤体润湿速度的效果有限。

In order to study the influence of a large number of pre-existing fractures on the moisture movement and wetting effect of coal seam in water injection,COMSOL Multiphysics was used to simulate the pressure field,velocity field and moisture increment in the process of water injection.At the same time,the random distribution model of three-dimensional pre-existing fractures in coal seam was established by programming with MATLAB.The results show that after the water injection of about 60 h,the velocity of water seepage in coal tends to be the same and remain relatively stable.The distributions of seepage moisture increment field,pressure field and velocity field are almost the same with their distributions in the early period of water injection.With a large number of pre-existing fractures being wetted by water,the fractures play the role of accelerating coal wetting speed as well as storing wa-ter.However,the effect of their acceleration of coal wetting speed is limited if these pre-existing fractures are not connected to boreholes.