Mechanism and effect analysis of enhanced gas drainage with large diameter double boreholes

Authors

ZHANG Chunhua, College of Safety Science and Engineering, Liaoning Technical University, Fuxin 123000, China
ZHANG Zijian, College of Safety Science and Engineering, Liaoning Technical University, Fuxin 123000, ChinaFollow
NIAN Jun, College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan 030000, China
JIAO Dengming, College of Safety Science and Engineering, Liaoning Technical University, Fuxin 123000, China

Abstract

To study the mechanism of enhanced gas drainage with large diameter double boreholes, numerical models of single holes with different diameters and double ø350 mm holes were established by using the RFPA^2D-Gas software in working face 30110 of Shiquan Coal Mine, Shanxi Province. Stress distribution, damage and fracture, gas permeability evolution and gas migration law of the coal around the hole were analyzed, and then the extraction effect of double ø350 mm holes was investigated. Simulation results show that the pressure relief radii of the ø100 mm, ø250 mm, ø350 mm and double ø350 mm holes are 0.25 m, 0.9 m, 1.2 m and 2.2 m, respectively. The coal damage extends to the upper left and upper right around the holes of ø250 mm, ø350 mm and double ø350 mm, and the final fracture shape is like spreading wings of a butterfly. The permeability coefficient of the coal at 1.5 m above the double ø350 mm holes can increase from 0.25 m²/(MPa²·d) to 240 m²/(MPa²·d). The gas migration rate increases with the increase of hole diameter, and gradually decreases in the drainage. However, when the coal around the hole is damaged, it will increase to a certain extent. The field investigation results show that the gas extraction effect is enhanced by the collapse of double ø350 mm holes. For the double ø350 mm hole, the drainage radius is 2 m, the gas flow can be 21 times that of the ø100 mm hole, and the total volume of extraction is more than 10 times and even 40 times of the ø100 mm hole.

Keywords

large diameter double boreholes, double ø350 mm hole, enhanced gas drainage, drainage radius, gas control, Shiquan Coal Mine

DOI

10.3969/j.issn.1001-1986.2021.06.033

Recommended Citation

ZHANG Chunhua, ZHANG Zijian, NIAN Jun, et al. (2021) "Mechanism and effect analysis of enhanced gas drainage with large diameter double boreholes," Coal Geology & Exploration: Vol. 49: Iss. 6, Article 34.
DOI: 10.3969/j.issn.1001-1986.2021.06.033
Available at: https://cge.researchcommons.org/journal/vol49/iss6/34

Reference

[1] LI Yuanlin, LIU Yong, WANG Chen, et al. Research and application of deep hole pre–splitting blasting technology for permeability enhancement in high gas and low permeability coal seam[J]. Journal of Safety Science and Technology, 2020, 16(9): 71–76. 李元林, 刘勇, 王沉, 等. 高瓦斯低透气性煤层深孔预裂爆破增透技术研究及应用[J]. 中国安全生产科学技术, 2020, 16(9): 71–76.

[2] MOU Quanbin, ZHAO Jizhan. Study on enhanced gas drainage technology of borehole gas based on mechanical borehole reaming[J]. Coal Science and Technology, 2015, 43(5): 58–61. 牟全斌, 赵继展. 基于机械造穴的钻孔瓦斯强化抽采技术研究[J]. 煤炭科学技术, 2015, 43(5): 58–61.

[3] ZHANG Xiaogang, JIANG Wenzhong, DU Feng. Development status and prospect of permeability enhancement technology in high gas low permeability coal seam[J]. Safety in Coal Mines, 2021, 52(2): 169–176. 张晓刚, 姜文忠, 都锋. 高瓦斯低透气性煤层增透技术发展现状及前景展望[J]. 煤矿安全, 2021, 52(2): 169–176.

[4] HUA Mingguo, WANG Kaiwang, FU Yongshuai, et al. Study on technology of controlling upper corner gas by super–large diameter borehole[J]. Coal Technology, 2020, 39(7): 122–125. 华明国, 汪开旺, 傅永帅, 等. 超大直径钻孔治理上隅角瓦斯技术研究[J]. 煤炭技术, 2020, 39(7): 122–125.

[5] YUAN Liang. Concept of gas control and simultaneous extraction of coal and gas[J]. China Coal, 2010, 36(6): 5–12. 袁亮. 瓦斯治理理念和煤与瓦斯共采技术[J]. 中国煤炭, 2010, 36(6): 5–12.

[6] WANG Yaofeng. Current situation and prospect of gas extraction technology and equipment for coal mines in China[J]. Safety in Coal Mines, 2020, 51(10): 67–77. 王耀锋. 中国煤矿瓦斯抽采技术装备现状与展望[J]. 煤矿安全, 2020, 51(10): 67–77.

[7] LI Dingqi. A new technology for the drilling of long boreholes for gas drainage in a soft coal seam[J]. Journal of Petroleum Science and Engineering, 2016, 137: 107–112.

[8] YIN Guangzhi, LI Minghui, LI Shengzhou, et al. 3D numerical simulation of gas drainage from boreholes based on solid–gas coupling model of coal containing gas[J]. Journal of China Coal Society, 2013, 38(4): 535–541. 尹光志, 李铭辉, 李生舟, 等. 基于含瓦斯煤岩固气耦合模型的钻孔抽采瓦斯三维数值模拟[J]. 煤炭学报, 2013, 38(4): 535–541.

[9] SI Hu, GUO Tao, L1 Xiaohong. Analysis and numerical simulation of fluid–structure coupling of gas drainage from boreholes[J]. Journal of Chongqing University, 2011, 34(11): 105–110. 司鹄, 郭涛, 李晓红. 钻孔抽放瓦斯流固耦合分析及数值模拟[J]. 重庆大学学报, 2011, 34(11): 105–110.

[10] YANG Tianhong, CHEN Shikuo, ZHU Wancheng, et al. Coupled model of gas–solid in coal seams based on dynamic process of pressure relief and gas drainage[J]. Rock and Soil Mechanics, 2010, 31(7): 2247–2252. 杨天鸿, 陈仕阔, 朱万成, 等. 煤层瓦斯卸压抽放动态过程的气–固耦合模型研究[J]. 岩土力学, 2010, 31(7): 2247–2252.

[11] LIU Jiajia, JIA Gaini, WANG Dan, et al. Study on optimization of gas drainage parameters with borehole drilled along seam based on coupling of multi physical field[J]. Coal Science and Technology, 2018, 46(7): 115–119. 刘佳佳, 贾改妮, 王丹, 等. 基于多物理场耦合的顺层钻孔瓦斯抽采参数优化研究[J]. 煤炭科学技术, 2018, 46(7): 115–119.

[12] SONG Haoran, LIN Baiquan, ZHAO Yang, et al. Effect mechanism of anisotropy and heterogeneity on gas seepage during coal seam drainage[J]. Journal of Xi'an University of Science and Technology, 2019, 39(3): 461–468. 宋浩然, 林柏泉, 赵洋, 等. 各向异性和非均质性对煤层抽采钻孔瓦斯渗流的影响作用机制[J]. 西安科技大学学报, 2019, 39(3): 461–468.

[13] DING Houcheng, JIANG Zhong'an, HAN Yunlong. Numerical simulation and application of boreholes along coal seam for methane drainage[J]. Journal of University of Science and Technology Beijing, 2008, 30(11): 1205–1210. 丁厚成, 蒋仲安, 韩云龙. 顺煤层钻孔抽放瓦斯数值模拟与应用[J]. 北京科技大学学报, 2008, 30(11): 1205–1210.

[14] LIANG Bing, YUAN Xinpeng, SUN Weiji. Seepage coupling model of in–seam gas extraction and its applications[J]. Journal of China University of Mining & Technology, 2014, 43(2): 208–213. 梁冰, 袁欣鹏, 孙维吉. 本煤层顺层瓦斯抽采渗流耦合模型及应用[J]. 中国矿业大学学报, 2014, 43(2): 208–213.

[15] JIA Bingyi, CHEN Dongdong, WU Jie, et al. Practice of enhanced gas extraction by staged fracturing with comb–shaped long hole in coal mine roof[J]. Coal Geology & Exploration, 2021, 49(2): 70–76. 贾秉义, 陈冬冬, 吴杰, 等. 煤矿井下顶板梳状长钻孔分段压裂强化瓦斯抽采实践[J]. 煤田地质与勘探, 2021, 49(2): 70–76.

[16] GUO Haijun, TANG Hanlu, WANG Kai, et al. Application of gas–solid coupling effect in the gas drainage with double boreholes along coal seam[J]. Journal of Xi'an University of Science and Technology, 2021, 41(2): 221–229. 郭海军, 唐寒露, 王凯, 等. 含瓦斯煤气固耦合作用在顺层双钻孔瓦斯抽采中的应用[J]. 西安科技大学学报, 2021, 41(2): 221–229.

[17] WANG Xian, XU Chao, WANG Siyi, et al. ø650 mm large diameter drilling technology and equipment for the coal seam[J]. Metal Mine, 2017(8): 157–160. 王鲜, 许超, 王四一, 等. 本煤层ø650mm大直径钻孔技术与装备[J]. 金属矿山, 2017(8): 157–160.

[18] CHEN Jiufu, WEI Jinzhong, ZHANG Guojiang, et al. Study on permeability improvement technology of the large–diameter drilling combined with hole protection[J]. Coal Science and Technology, 2018, 46(10): 73–77. 陈久福, 魏晋忠, 张国江, 等. 大直径钻孔联合孔内下套护孔增透技术研究[J]. 煤炭科学技术, 2018, 46(10): 73–77.

[19] LI Fei, XUE Yanping, ZHAO Kaikai, et al. Application of large diameter drilling in coal seam for gas control[J]. Coal Engineering, 2021, 53(3): 84–88. 李飞, 薛彦平, 赵凯凯, 等. 煤层大直径钻孔瓦斯治理技术研究与应用[J]. 煤炭工程, 2021, 53(3): 84–88.

[20] YAO Xiangrong, CHENG Gonglin, SHI Biming. Analysis on gas extraction drilling instability and control method of pore–forming in deep surrounding–rock with weak structure[J]. Journal of China Coal Society, 2010, 35(12): 2073–2081. 姚向荣, 程功林, 石必明. 深部围岩遇弱结构瓦斯抽采钻孔失稳分析与成孔方法[J]. 煤炭学报, 2010, 35(12): 2073–2081.

[21] MA Zan, CHEN Dongdong, XIE Hengxing, et al. Gas drainage borehole completion technology of directional long hole drilling with negative angle[J]. Coal Geology & Exploration, 2021, 49(3): 62–68. 马赞, 陈冬冬, 解恒星, 等. 负角度定向长钻孔瓦斯抽采完孔工艺研究[J]. 煤田地质与勘探, 2021, 49(3): 62–68.

[22] PANG Bo. Problems and countermeasures of gas drain technology in coal mine[J]. Modern Chemical Research, 2019(11): 47–48. 庞渤. 煤矿瓦斯抽放技术存在的问题及对策[J]. 当代化工研究, 2019(11): 47–48.

[23] TANG Chun'an, RUI Yongqin, LIU Hongyuan, et al. Numerical simulation to outburst mechanism of coal or rock containing gas with RFPA^2D system[J]. Journal of China Coal Society, 2000, 25(5): 501–505. 唐春安, 芮勇勤, 刘红元, 等. 含瓦斯"试样"突出现象的RFPA^2D数值模拟[J]. 煤炭学报, 2000, 25(5): 501–505.

[24] XU Tao, YANG Tianhong, TANG Chun'an, et al. Numerical simulation on coupled solid–gas flow in failure process of gaseous coal and rock[J]. Journal of Northeastern University(Natural Science), 2005, 26(3): 293–296. 徐涛, 杨天鸿, 唐春安, 等. 含瓦斯煤岩破裂过程固气耦合数值模拟[J]. 东北大学学报(自然科学版), 2005, 26(3): 293–296.

[25] ZHANG Chunhua, ZHANG Weiliang, WANG Jiren. Mechanical control effect of hard tectonic structure on coal seam gas flow[J]. Journal of Chongqing University, 2014, 37(9): 113–118. 张春华, 张卫亮, 王继仁. 硬质体构造对煤层瓦斯流动的力学控制效应[J]. 重庆大学学报, 2014, 37(9): 113–118.