Experiment study on physical simulation of gas drainage effect under the condition of different gas pressure

In order to study the gas pressure evolution features during the seam gas drainage process and the different initial gas pressure affected to the gas drai nage, a self developed physical simulation test system of the multi coupling coalbed methane mining was applied to the physical simulation test study on the gas draina ge under the different gas pressure.The results showed that, during the gas drainage process, the gas pressure would be quickly decreased with the time passed in the initial period and would be decreased slowly at the late period.Meanwhile, the gas pressure gradient would be high in the vertical borehole and the gas pressure gradie nt in the parallel direction drilling would be low.The 3D surface map prepared showed that the cross section gas pressure curve surface would be a funnel-shaped distri bution with the gas drainage borehole as the central axis and the level and longitudinal gas pressure curve surface would be in a V shape distribution.The higher the init ial gas pressure is, the higher absolute reduction would be during the gas drainage process, the decreased speed of the gas pressure would be faster.But during the ga s drainage process, the relative decreasing rate of the gas pressure would not be high and the residual gas pressure would be closed when the gas drainage was ende d.The results can provide guidance for the site gas drainage.