| This thesis focuses on the problem that the gas drainage rate of ChangCun coal mine 37 coal seam is low to undertake research and intends to use underground coal seam CO2 injection to improve gas drainage rate on the premise of the traditional method of gas drainage is not effective.Through theoretical research,the research ideas of field test,laboratory test,numerical simulation and field test are worked out.The results of field test show that the original gas pressure of coal seam is 0.82MPa.The results of industrial analyzer for coal samples are obtained through the laboratory experimental.The gas content of coal seam is 10.2 m3/t,which calculated by indirect method.Some conclusions are obtained by numerical simulation.First,the effective radius of gas injection is positively related to injection pressure,extraction pressure and borehole diameter,and is exponential function with the extraction time.Second,There is a logarithmic function between the drilling interval and the extraction time.At last,the effect of gas injection is better than that of pure extraction and the effective radius increased by 1.16-1.8 times at the same time.Field tests show that when the same effective radius is reached,the time of CO2 injection is shorter 65%87%than that of Simple drainage under the same conditions,and pure gas flow rate increased by 3 times after gas injection.Therefore,the 3#coal seam of ChangCun coal mine can increase the gas extraction rate by injecting Co2,and the research provides a new approach for improving the gas drainage rate of single soft and low permeability coal seam. |
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