Based on the self-developed multi-field coupling testing system for coalbed methane exploitation

a series of physical simulation experiments of gas drainage under different spacing distances between boreholes was conducted to investigate the evolution of gas pressure and gas flow rate during drainage process. The results show that the gas pressure at different measuring points in the coal seam drops faster with the decrease of the distance from the drainage pipe. With the influence of the drainage superimposed effect

the gas pressure drop rate of areas between the drainage pipes is greater than that of the outside under the same distance condition

and the pressure difference rapidly reaches the peak value after the start of drainage

and then drops. The closer to the drainage pipe or with the increase in the borehole spacing

the less the effect of the superimposed effect is. There exists a power function relationship between pressure gradient and instantaneous flow rate on the section of the coal seam perpendicular to the borehole. With the increasing amounts or decreasing spacing of boreholes

the gas pressure of the same position drops faster

the instantaneous flow rate decreases

the cumulative flow rate increases

and the value of coal seam permeability coefficient “ɑ” increases

indicates that the gas drainage efficiency is higher. It can provide theoretical basis for reasonable arrangement of boreholes.