Research On Determination Method Of Effective Radius Of Coal Seam Gas Drilling Drainage

As one of the main disasters in coal mine safety exploitation,gas disaster has been paid attention to.At present,in the prevention of gas disaster,the pre drainage of coal seam gas is the key means to prevent coal and gas outburst and underground gas exceeding standard.In order to ensure the quality,it is critical to allocate the drilling distance and pre pumping time scientifically,but the key to design the drilling distance is the extraction radius.Drainage radius by various factors,so the planning stage are of great value to rapid,reasonable and accurate evaluation of the radius of the hole drainage,has very important significance to ensure the safety production of coal mine.By means of theoretical analysis,numerical simulation and field test,the regularities between effective radius of borehole extraction and time of extraction are studied.With the basic parameters of gas laboratory determination of Handan Fengfeng Yangdong mine 2#coal seam,derived using percolation mechanics theory of gas drainage radius and effective drainage coupled mathematical model of interaction between the time,with the help of COMSOL Multiphysics software,the gas drainage radius and time curves of each other,finally clear the specific value of gas drainage recovery the radius of the.Handan Fengfeng Yangdong mine 2#coal seam as the test point,according to the requirements of the "Interim Provisions" standard drainage of coal mine gas,reducing method and SF6 tracer gas of the coal seam to ?94mm??113mm??133mm borehole and borehole pumping the practical investigation mining radius using gas pressure,and the measured data analyze.Research shows that with the increase of extraction time,gas pressure around the borehole to borehole as the center,from the drainage pressure began to rise,the longer the drainage,the scope of influence of the gas pressure in coal seam is bigger;the closer the distance from hole,the gas pressure gradient is large,opposite the greater distance from hole and the gas pressure gradient is smaller,gradually close to zero,the gas pressure rises to the original gas pressure,eventually forming a drainage"gas pressure funnel";based on the drainage time did not change,from the borehole spacing is close,the seepage rate is higher;on the contrary from hole farther,the seepage rate the smaller,with the continuous improvement of extraction time,the flow rate also decreased,eventually approaching a standstill;drainage radius with the increasing permeability increases with the increase of permeability The effective radius of gas extraction increases with the increase of pumping time.The Handan peak Yangdong mine 2#coal seam borehole and borehole drilling in the scope of the study(phi 94mm-phi 133mm)within the drainage radius and the diameter of the hole has a certain relationship,the hole diameter increases,the effective drainage radius increases with prolonging extraction time,the hole diameter of the effective drainage radius of influence larger.