Study On Coal Seam Permeability Enhancement Of Powder Liner Perforating Charge

With decades of high-intensity coal mining,the depth of mining in Shandong,Shanxi,Northeast and other places in China's traditional coal mining provinces has been extending continuously.The mine conditions are more complex,the traditional coal mine disaster gas,water damage and rock burst are more serious.The gas content in coal seam is getting higher and higher,and the risk of gas outburst is increasing.But the average gas drainage rate and utilization rate in our country are still very low.It is urgent to find a more efficient and secure way of managing and utilizing gas.This thesis applies the mature perforation technology in the petroleum field to gas drainage,which can greatly reduce the gas content in the coal seam,shorten the pre-drainage time,improve the economic efficiency,and provide a new way for coal mine safety mining and gas drainage.This technology can also provide a gas source guarantee for surface coalbed methane collection and utilization and has a broad prospect.Combining the theoretical simulation and the experiment of shaped jet,the aims of thesis to study the effect of perforating charge penetrating coal seam,analyze the crack evolution and stressed change of coal seam target plate after penetration,and demonstrate the feasibility and safety of perforation technology in coal seam penetration.Using the simulation software LS-DYNA to establish a three-dimensional model,the process of perforating charge jet formation and penetration into coal seam was numerically simulated,and the effect of perforation through coal seam was compared with the blasting effect of conventional slotted charge roll blasting.The results show that the penetration depth was 250%higher than that of conventional slotted charge roll blasting,and the effective area was increased by 2592%,which provides a theoretical basis for the application of perforation technology in low permeability coal seam.The effects of metal liner cover on the jet formation and penetration of coal seam at four angles of 60°,70°,80°and 90°and the clipping radius of 1 mm,2 mm,3 mm and 4 mm were analyzed.Finally,it was determined that the liner angle was 80 ~o and the truncation radius was 2 mm.Based on the simulation results and the objective conditions of the coal mine,the shaped charge structure suitable for coal seam antipenetration was designed.The penetration effects of copper powder metal liner and dense copper on large coal lump in Wuyang Coal Mine were obtained under the same structure by experiments,and the combination of experimental results and economic and other factors to determine the use of copper powder metal liner.There is a big gap in coal seam strength due to the different burial depth and metamorphic degree of coal seam.Therefore,for different coal seam strength,it is necessary to reasonably set various parameters such as drill hole diameter,hole spacing,charge height of perforating charge,sealing length and so on.The purpose to ensure that the operation can be carried out economically,efficiently and safely in the complex underground mining environment.This experiment is very close to the simulation,which shows that it is feasible to use numerical simulation to design special perforating charges for different coal seams and to work out reasonable technology and safety measures.