Guo Jun, Zhang Xuanchi, Liu Yin, Cai Guobin, Liu Hua, Chen Changming, Wang Lei
College of Safety Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.
Key Laboratory of Western Mine and Hazard Prevention, Ministry of Education of China, Xi'an 710054, China.
ACS Omega. 2024 Sep 12;9(38):39387-39400. doi: 10.1021/acsomega.4c02672. eCollection 2024 Sep 24.
To address the challenges associated with the high gas content, high pressure, and low permeability coefficient in deep coal seams, strategies such as infilling boreholes and increasing the negative pressure of extraction are commonly implemented to alleviate issues related to coalbed methane extraction. However, long-term mining pressure can lead to the development of cracks in the coal seam near the borehole, thereby creating air leakage channels, which could potentially impact the oxygen supply during the extraction process. This leads to secondary disasters such as the spontaneous combustion of coal and gas explosions, considerably impacting the life and health of underground workers. To solve this issue, a thermal-fluid-solid coupling model for the working surface was constructed based on numerical simulation software, taking into account the multimechanism coupling effect of coal seam gas. The laws of coal oxidation and spontaneous combustion induced by coalbed methane extraction around boreholes were studied. The variation laws of the oxygen concentration, coal temperature, and oxidation heating zone around the borehole under different extraction conditions were simulated and analyzed. The findings demonstrate that the negative extraction pressure enables the gas to penetrate the fracture zone of the borehole, leading to an increase in the oxygen consumption rate and coal temperature around the borehole with an increase in negative extraction pressure. The coal gas leakage surrounding the borehole reduces as the sealing depth increases, and both the heating rate of coal and oxygen volume fraction show a downward trend. The fitting relationship between the negative pressure of drainage, depth of sealing, and temperature change in the coal body surrounding the boreholes was identified. It was determined that the negative pressure of 13 kPa for borehole drainage and a sealing depth >18 m are the optimal extraction parameters. The range of the oxidation zone and the position of the boundary line under this parameter were predicted, and the position function of the dangerous area of oxidation heating was defined. The research results have remarkable implications for the coordinated prevention and control of gas and coal spontaneous combustion in coalbed methane predrainage boreholes, as well as for efficient prevention and control of CO in on-site gas extraction boreholes, thus ensuring efficient and safe gas extraction.
为应对深部煤层瓦斯含量高、压力大、渗透系数低等相关挑战，通常采用钻孔充填、增加抽采负压等策略来缓解煤层气抽采相关问题。然而，长期开采压力会导致钻孔附近煤层出现裂隙，从而形成漏气通道，这可能会影响抽采过程中的氧气供应。这会引发煤炭自燃和瓦斯爆炸等次生灾害，对井下工人的生命和健康造成重大影响。为解决这一问题，基于数值模拟软件构建了工作面热 - 流 - 固耦合模型，考虑了煤层瓦斯的多机制耦合效应。研究了钻孔周围煤层气抽采引发的煤炭氧化与自燃规律。模拟分析了不同抽采条件下钻孔周围氧气浓度、煤体温度及氧化发热带的变化规律。研究结果表明，抽采负压使瓦斯能够穿透钻孔裂隙带，随着抽采负压的增加，钻孔周围的氧气消耗速率和煤体温度升高。随着封孔深度增加，钻孔周围的煤层瓦斯泄漏量减少，煤体升温速率和氧气体积分数均呈下降趋势。确定了钻孔抽采负压、封孔深度与钻孔周围煤体温度变化之间的拟合关系。确定钻孔抽采负压为13 kPa、封孔深度大于18 m为最佳抽采参数。预测了该参数下氧化带范围及边界线位置，定义了氧化发热危险区域的位置函数。研究结果对于煤层气预抽钻孔瓦斯与煤炭自燃的协同防治以及现场瓦斯抽采钻孔中CO的高效防治具有重要意义，从而确保瓦斯高效安全抽采。
