Ren Zhongjiu, Wang Haifeng
School of Safety Engineering, China University of Mining and Technology, Xuzhou, Jiangsu Province 221116, China.
Shenyang Research Institute, China Coal Technology and Engineering Group, Fushun, Liaoning Province 113122, China.
ACS Omega. 2023 Jul 11;8(29):26035-26044. doi: 10.1021/acsomega.3c02126. eCollection 2023 Jul 25.
Large diameter borehole drilling in fractured soft coal seam may lead to problems such as drilling blockage, perforation, and hole collapse. The protective screen pipe in the drilling hole can support the damaged coal, prevent the drilling blockage, and improve the coal permeability. The mathematical model of gas drainage by large diameter borehole in fractured soft coal seam was established. Taking the 3205 working face in Shanxi Fenxi Zhongxing Coal Mine as the background, the numerical simulation was carried out by importing the mathematical model into COMSOL Multi-physics software to study the gas migration law around large boreholes with protective screen pipe in fractured soft coal seam. The results show that the gas flow velocity in section A of the borehole and pipe is between 0 and 0.25 m/s, and the gas flow velocity in the borehole is smaller than that in the pipe and screen hole. The gas velocity in the borehole is lower than that in the protective screen pipe. In the large diameter borehole, the protective screen pipe can support the collapsed coal and prevent the borehole blockage. The free gas in the borehole can be quickly extracted out through the screen holes, which ensures the gas extraction efficiency. The results provide a guidance for promotion and application of the technology of large diameter borehole with protective screen pipe in field.
在破碎软煤层中进行大直径钻孔可能会导致钻孔堵塞、穿孔和孔壁坍塌等问题。钻孔中的保护筛管可以支撑破碎的煤体，防止钻孔堵塞，并提高煤层透气性。建立了破碎软煤层大直径钻孔瓦斯抽采的数学模型。以山西汾西中兴煤矿3205工作面为背景，将数学模型导入COMSOL多物理场软件进行数值模拟，研究破碎软煤层中带保护筛管大钻孔周围的瓦斯运移规律。结果表明，钻孔与筛管A断面处瓦斯流速在0～0.25m/s之间，钻孔内瓦斯流速小于筛管及筛孔内瓦斯流速，钻孔内瓦斯流速低于保护筛管内瓦斯流速。在大直径钻孔中，保护筛管能够支撑垮落煤体，防止钻孔堵塞，钻孔内游离瓦斯能够通过筛孔快速抽出，保证了瓦斯抽采效率。研究结果为带保护筛管大直径钻孔技术在现场的推广应用提供了指导。
