Abstract
Gas extraction is an important way to control gas disasters. The effect of traditional gas extraction drilling on ultrathick coal seam is not well. In order to improve the rate of gas extraction, directional long drilling is used to replace conventional drilling for coal seam gas extraction. Through the combination of numerical simulation and field experimentation, the stress distribution around borehole is analyzed, and the influence of different time, different gas pressure, different negative pressure of extraction, and different permeability of coal body on directional borehole is simulated. According to the experimentation of Baode Mine, the data of gas drainage volume of conventional directional drilling are recorded and analyzed. The results indicate that the directional drilling is more suitable for Baode Mine 81306 working face of coal seam 8 gas extraction operation. Directional drilling is better than conventional drilling in work, with good drainage stability and large gas drainage volume, which can greatly reduce the outburst time and improve the gas drainage rate.
Highlights
According to data from the Ministry of Ecology and Environment of China, from 2010 to 2020, the proportion of coal consumption in China’s primary energy consumption structure decreased from 69.2% to 56.8%
The geological conditions of coal seam occurrence in China are very complicated, and the permeability of coal seam is low, which leads to the emergence of many risk factors in the process of coal mining, among which the gas disaster is the most serious
Because the effective area of directional drilling on coal seam is large, the original stress distribution of coal body can be changed in a large range, and the dynamic equilibrium of adsorption and desorption can be broken, so that the gas is transformed from adsorption state to free state
Summary
According to data from the Ministry of Ecology and Environment of China, from 2010 to 2020, the proportion of coal consumption in China’s primary energy consumption structure decreased from 69.2% to 56.8%. Achieved good drainage effect [21, 22]; Wang conducted numerical simulation on directional long borehole of gas extraction in medium and hard coal seam, analyzed the influence degree of drilling length and spacing on gas extraction by drilling hole, and provided reference for the analysis of other influencing factors of gas extraction drilling [23–25]; Chen and Luo used long boreholes in bedding to prepump working face and transport pipeline, which saved the time of eliminating outburst and completed the technological innovation experiment project of “one borehole and two eliminating” in long drilling holes in bedding [26]; Zhang et al studied the directional long drilling equipment at domestic and abroad, found out the problems existing in the application of RIGS drilling abroad under the geological conditions of coal seams in China, and put forward the corresponding opinions on optimization of compatibility [27].
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