Extraction Technology Research Of High Pressure Pulse Water Splitting For Increasing The Permeability In Low Permeability Coal Seam

High efficiency gas extraction is one of the necessary means to prevent coal and gas outburst and reduce gas accident.But with the increase of the mining depth,the low permeability of coal seam is the common situation of mine in our country,which is also the main problem of the gas extraction.The coal deposit is more than 1000m,the gas content is 12.7?30m3/t,and the permeability coefficient of the coal layer is 0.004?0.224m2/(MPa�d),which is low permeability and hard to draw coal seam in VI group coal seam of Pingmei NO.10 Coal Mine.Aiming at the status,in this thesis adopts the research of high-pressure pulse water splitting for increasing the permeability in low permeability coal seam is carried out,the aim is to increase the permeability of coal seam,the prevention of coal and gas outburst,improve the efficiency of gas extraction.In the thesis the 24080 working face of VI-15coal seam of Pingmei NO.10 Coal Mine is the engineering background and the research for increasing the permeability of the coal seam is in-depth study by means of theoretical research,laboratory test,field test and numerical simulation on low permeability coal seam.First of all,the basic parameters such as coal sample density,tensile strength,shear strength is measured in the laboratory to obtain the characteristics of the mechanical properties of coal then,theoretically,the mechanism of high pressure hydraulic action is analyzed,and the effect of the pulse effect on the gas desorption and the influence of high pressure water on gas seepage is analyzed.Further,the optimal separation pressure interval was 15-20MPa through the testing of high-pressure water splitting,In the experiment,the radius of the high pressure pulse is 1.0m,the radius of influence is 4.0m.All these provide reference for the gas extraction drilling.The permeability coefficient of the coal seam is changed to be an indicator of the effect and the increase of the permeability of coal seam in the area of the increase of permeability can be increased from several tens to hundreds of times.The gas extraction model is established based on the test result and the field.The simulation results are shown that under the same conditions,increasing the permeability of coal seam can reduce the negative pressure of the gas and expand the spacing.In order to optimize the gas extraction process,the holes of boreholes,negative pressure and hole spacing were studied after the permeability is increased.It is included that the-15KPa pressure drilling borehole is 3m,-20KPa for 7m,-22KPa for 9m at beginning of hole space The main key technology of rapid unloading and increasing permeability is obtained.In the end,based on the field test and numerical simulation results,the application of the extraction process is made.In the application,the gas concentration of the borehole gas was basically stable between 80%and 90%,and the gas flow was 0.05m3/min-0.08m3/min.There is no gas limit in the backwind,and the construction time and gas extraction cost are greatly saved.This study is of great significance to the increase of the low permeability coal seam in Pingmei NO.10 Coal Mine,and also provides good reference for other similar mines.