Research On Three-dimensional Comprehensive Gas Pre-drainage Technology And Application In Huangling Mining Area

With the increasing depth and intensity of underground mining,the amount of gas emission from the working face has gradually increased,and a large part of this comes from the goaf.Therefore,strengthening the control of gas in the goaf is the primary task to ensure the safety of the working face.In this paper,theoretical research,experimental analysis and numerical simulation are combined to analyze the thickness distribution of No.2 coal seam and the distribution of oil-type gas in the roof and floor of 205 working face,and study the source and composition of gas emission in the goaf.This paper puts forward a method for optimal layout of long directional boreholes in surrounding rock and the layout of boreholes,which comprehensively considers the impact of mining on the roof and floor damage and the distribution of surrounding rock gas reservoirs.Designed the top and bottom directional drilling 2 and 3 casing hole structure,determined the relevant parameters of the drilling trajectory and the directional drilling trajectory.Designed and constructed 9 No.2 coal seams with 5,473m boreholes,5 roof holes 2,709m,3 bottom plate holes 1,353m,and 7 No.3 coal seam bores of 2031m and directional drilling.The construction method of directional drilling in the area was studied.The geological stratum recognition while drilling technology through the color of the backwater,touching the cuttings and observing the dry cuttings was developed,and the drilling construction technology was summarized,forming a comprehensive three-dimensional gas drainage technology with full spatial coverage.The relationship between the drainage data and the exposure level of the borehole and the layout of the borehole was studied,and the gas concentration in the upper corner of the working surface was compared with the gas concentration in the front and back working faces.The comprehensive three-dimensional drainage can be seen from the concentration and volume of the borehole drainage.The drilled boreholes had obvious effects on exposure and drainage before mining,pressure relief drainage during mining,and drainage after mining.The gas concentration in the upper corner dropped from 0.81%to 0.48%,a 41%drop.The coal seam’s directional long boreholes have a gas drainage volume of 0.0022～0.144m~3/min,and a drainage concentration of 8%～95%.After 24 months of drainage,the gas drainage volume of a single hole has reached 12.26～196.5 thousand.m3.The coal seam gas content is reduced from 3.01m~3/t to 1.56～1.73m~3/t,the pressure is reduced from 0.65MPa to 0.19～0.28MPa,and the gas pre-drainage rate reaches 42.52%～48.17%.The research and application results show that the three-dimensional comprehensive pre-drainage gas drainage technology proposed in this paper can effectively control the problems of gas accumulation in the upper corner and gas overrun in the goaf,in order to eliminate gas accumulation in the upper corner and avoid gas overrun Provides a new way of thinking.