Optimization Of Process Parameters And Application Of Along Seam Long Drilling Used For Pre-pumping Coal Seam Gas

According to the question that coal and gas outburst become serious and sophisticated daily as a result of improvement of stratum stress, gas pressure, gas content and decline of permeability coefficient as mining to the depth of the basic entry-600m deep in coals belong to Huainan Mining Industry (Group) Co., Ltd, the paper carries out the research of along seam long drilling used for preventing coal and gas outburst by theoretical analysis, field expedition and numerical simulation methods using Pan-yi mine and Pan-san mine as experimental mine. The purpose is to reduce construction volume, improve pumping rate, shorten the cycle of outburst and achieve safe and fast driving.Along seam long drilling can relieve pressure and enhance permeability by reducing stratum stress, decend gas dynamic and release of gas potential power by drainage gas from coal seam, eliminate the risk of coal and gas outburst by expanding relief area. After the measures of along seam long drilling is taking, the status of stress balance is breaken in front of mining face in coal and rock containing gas. And then concentrated stress transfers to the deep coal which expands the width of relief bands. At the same time the paper analysises the relationship between relief bands and the risk of coal and gas outburst and calculates the minimum width of safe relief bands is 4.4~7.7m for 11-2 coal in Ding-ji mine.The paper simulates the difference of gas pressure distribution around the drilling with different depth and diameter of drillings in the case of only one drilling and with different spacing aparting from one drilling to another drilling in the case of two drillings by using Multi-physics coupling Simulation software. Conclusions are as follows: the range of along seam long drilling increases as the improvement of depth and diameter of drillings, but gradient of increasement decreases gradually. The maximum control radius can reach 2.13m on both sides of the drilling in the case of only one holes.The rate of decline of gas pressure around holes aparting from each other 2m is faster than holes aparting from each other 3m. Moreover, the effect of eliminating the risk of coal and gas outburst is more obvious.The paper introduced the applications and effect expedition of along seam long drilling in Pan-yi mine and Pan-san mine. After the measure was taken, residual gas content declined under the gas content of opening outburst, Pre-pumping rate of gas exceeded 30% and the driving speed improve two times in all this three mines. All the efficiency review indicators were not excessive in Pan-yi mine and Pan-san mine. According to the question that indicators used for evaluating the risk of coal and gas outburst are not reasonable, the paper determined gas parameters of opening outburst through laboratory simulation, historical data analysis and on-site inspection. And the results are as follows: gas pressure of opening outburst is 0.74MPa, gas content of opening outburst is 4.50m3/t.Through the above study, the paper analysised the mechanism of eliminating the risk of coal and gas outburst of along seam long drilling in theory.Then the paper determined the effect of construction technology of along seam long drilling to the distribution of gas around drillings which supply basis for arranging holes reasonably. At last the paper shows that along seam long drilling can achieve the purpose to eliminate the risk of coal and gas outburst effectly and achieve safe and fast driving.