Study Of The Application Of Water Seal Technique In Gas Drainage Borehole

Gas drainage is an important method in controlling gas disasters in coal mine.The extracted gas can not only be used as clean energy,but also reduce environmental pollution caused by greenhouse.The seal technique is the important component of degassing.The seal quality determines the concentration and the extraction of degassing.Although the total gas production in China is large,the gas utilization rate is low,due to the fluctuation of the extraction concentration.In fact,the quality of seal drilling directly influences on the effect of degassing.Therefore,the study of coal seam drilling and high-efficiency sealing technique is of great significance in coal-mine safety production.This study takes Changcun Coal Mine as a case,uses the theoretical analysis,numerical simulation,field test,etc.,and investigates the pore structure of coal-seam fracture,the interaction of coal-rock dual medium structure,gas emission of the working face in protective layer,destroyed part and gas transfer.Then,the use of numerical simulation is to research on the numerical analysis of the distribution of the injected slurry around the drilling,and optimize the grouting length of each part of the sealing section based on simulation results.The research also uses the dual structure features and the distribution of mining stress to seal the drilling,based on the mechanical seal theory as well as the studies of gas drainage,seal technique and materials at home and abroad.Besides,the paper discusses the influence factor and seal difficulty of excavating the sealing pit from the change of fracture and permeability.Also,the study investigates the grounting mechanism,improvement of borehole sealing and coal-rock grouting to improve the strengthen of coal rock in order to make some coagulable mud crack into coal and bed rock.The new structure with high permeability and stability improves the physical and mechanical properties as well as stability of coal and rock mass.Finally,the study proposes a fluid seal technique,and investigates the seal performance by physical experiment and field test,in terms of the basic characteristics.According to the distribution of the fracture field around the drilling,the study establishes the flow model around the drilling,and finds that the diffusion distance of slurry increases with an increase in grouting pressure within a certain range.The results show that the equivalent continuum model of the continuum model is determined by establishing the equivalent continuum model of coal body grouting.The experimental results in the use of 6 chemical reagents shows that HV—CMC water solution with 1:40 is selected as the collosol for sealing drilling.As time goes on,we find the average concentration of between 30%and 60%in using the average concentration of fitting exponential function,and quickly detects the initial concentration in 20-day continuous decrease rate,and average gas concentration in test well is 74.20%,which is higher 62.72%compared with 45.60%in original well.