Numerical simulation analysis of effective gas drainage area in different number of drillings

In order to clarify the influence of the number of drillings on the coal seam gas pressure and the effective drainage area, the spatial distribution characteristics of the coal seam gas pressure and the effective drainage area with different number of drillings in a single row were calculated and analyzed by three-dimensional numerical simulation.The results show that: the change of the coal seam gas pressure has significant temporal and spatial response characteristics, in the early stage of drainage, the number of drillings has little influence on the gas pressure of coal seam beyond the drainage radius, however, the influence of the number of drillings gradually appears with time, the influence radius of gas drainage increases, and the downward trend of gas pressure is accelerated; the spatial distribution pattern and range of the effective drainage area of drillings are affected by the number of drillings and the drainage time; the relationship between the volume of effective drainage area and time is a function of y=ax^b and the volume of effective drainage area does not change linearly with the number of drillings; there is superposition effect between drillings in the process of gas extraction, which is more obvious with the increase of extraction time.