| Gas seepage characteristic parameters are the basis for mastering coal mine gas occurrence laws,disaster control,risk prediction,and coalbed methane development and utilization.Accurate determination of gas seepage characteristic parameters is a vital basic work in coal mine gas disaster prevention and production and mining.In the current stage of mine production,the direct method is usually used to determine the seepage characteristic parameters.The accuracy of the direct method is good,but the measurement cycle is too long.With the continuous advancement of mining technology and equipment,and the shallow coal resources in my country have gradually depleted,coal mining extends to the deep,and the gas storage conditions are becoming more and more complicated.The outburst hazard increases,and the accurate and rapid determination of gas seepage characteristic parameters can ensure the safety of mining,but the direct method has been unable to meet the needs of rapid mining in modern coal mines.The pressure recovery curve technology is derived based on the theory of groundwater dynamics in the oil field.This method has become an indispensable method in the development of oil and gas fields.Applying the analysis methods and inferences applied to oil wells to coal seams has the same role as oil wells in guiding safe production.This thesis mainly studies the gas pressure recovery curve method suitable for the measurement of gas seepage characteristic parameters of coal seams in coal mines,and develops a gas pressure measurement device for depression holes passing through the aquifer.The shape of the pressure recovery curve is analyzed by numerical simulation.Guide coal mine gas drainage,prevention of coal and gas outbursts,and high-efficiency gas drainage.The full text has achieved the following main research results:(1)Analyzed the sealing method when the downward borehole passes through the aquifer,and developed a pressure measurement method for the downward borehole sealing for the water outlet close to the coal seam,that is,the high-pressure fixed-point sealing method.The ultra-long sealing capsule was customized according to the method,and its sealing effect was investigated on the spot.The theoretical shape characteristics of the coal seam pressure recovery curve in the Huaibei mining area are statistically analyzed,and the pressure recovery curve shapes of multiple pressure measurement boreholes in 9 mines adjacent to each other in the same Huaibei mining area are studied,and the corresponding coal seam gas pressure recovery in the Huaibei mining area is obtained.Curve shape.(2)Based on the theory of dual-porous medium and coal seam gas flow theory,the coal seam gas flow equation during pressure measurement is established,and the gas pressure temporal and spatial distribution characteristics of 10 coal seams in Taoyuan Coal Mine ?1 mining area are simulated and analyzed,and the curve conforms to the Compertz curve model.The gas pressure recovery curve measured by the high-pressure fixed-point sealing method on site is consistent with the simulation results,which verifies the accuracy of the pressure measurement results.The Langmuir equation is used to calculate the coal seam gas pressure,and the calculation result has very little error with the gas pressure measured by the high-pressure fixed-point sealing device,which further verifies the accuracy of the gas pressure measurement method.(3)The stage characteristics of the theoretical shape of the pressure recovery curve are analyzed,and the slope section of the gas pressure curve is determined by the stage division of the pressure recovery curve and the analysis of the shape characteristics.The pressure recovery curve method obtained was applied to the on-site measurement of the air permeability coefficient of the coal seam,and the air permeability coefficient of the 10 coal seams in Taoyuan Coal Mine was calculated according to the pressure recovery curve.(4)In Taoyuan Coal Mine,the widely used radial flow method is used to measure the coal seam permeability coefficient,and the coal seam permeability coefficient calculated by the gas pressure recovery curve method is compared and analyzed.Through analysis,it is concluded that the two have the same growth trend,and the numerical calculation results are all within the difficulty of coal seam gas drainage that can be extracted.In engineering practice,the coal seam permeability coefficient is distinguished by orders of magnitude,and this error is acceptable.Has no influence on the determination of coal seam permeability level.The comparison shows that the gas pressure recovery curve method can greatly shorten the measurement time,and the calculation is simpler than the radial flow method,and fewer parameters are required.This paper has 40 figures,18 tables,and 82 references. |
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