Mechanism and application of cross-interface fracturing for permeability enhancement through the roof blasting of tectonic coal seams

Authors

GAO Kui, School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China; Scientific and Technological Research Platform for Disaster Prevention and Control of Deep Coal Mining, Anhui University of Science and Technology, Huainan 232001, ChinaFollow
WANG Youwei, School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, ChinaFollow
QIAO Guodong, School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China
TIAN Yu, School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China
FU Shigui, School of Safety Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China

Abstract

Deep coal mining is challenging due to deteriorating geological conditions. After undergoing multiphase tectonic movements, primary coals have evolved into soft tectonic coal seams with low permeability and high gas content, complicating drilling in coal seams. In this case, the blasting-induced fractures are not well-developed and are prone to be re-compacted. So far, no fundamental breakthrough has been achieved in the key technology of fracturing for permeability enhancement technology through the roof blasting of tectonic coal seams. Given this, this study established test models for similar simulation tests and numerical analysis on the roof blasting of coal seams. By monitoring the cross-interface stress wave propagation and the macroscopic three-dimensional fracture evolutionary morphologies, this study reproduced the blasting stress wave propagation, as well as the internal damage and failure processes of coals and rocks. Key findings are as follows: (1) The blasting-induced damage to tectonic coal seams is primarily distributed in blasting boreholes and coals near the upper and lower coal-rock interfaces. The roof blasting of tectonic coals produces cross-interface fractures for pressure relief, and the blasting-induced damage propagates along blasting boreholes to the surrounding rock masses, ultimately spreading to the footwall of coal seams. Serious damage is found in blasting boreholes, near the upper coal-rock interfaces, and inside coal seams. (2) The blasting stress waves undergo transmission and reflection when propagating to coal-rock interfaces from the roof of the tectonic coal seams. The transmitted compressive stress waves damage coals, while the reflected tensile stress waves react on the rock masses at coal-rock interfaces. (3) The pressure relief induced by cross-interface fractures, generated by blasting-induced cumulative damage, connect the rock fractures on the roof with the fractures within tectonic coal seams, facilitating the vertical migration of gas in tectonic coal seams and gas drainage with stress relief. The on-site application shows that gas drainage following the roof blasting of coal seams manifested rapidly increased pure gas flow and concentration, which increased from 0.07 m³/min to 1.73 m³/min and from 10.46% to 68.50% (volume fraction), respectively and maintained at high levels for a prolonged period. The results of this study can provide a theoretical basis and technical support for efficient gas drainage from deep tectonic coal seams.

Keywords

tectonic coal, simulation test, blasting for pressure relief, coal seam permeability enhancement, gas control

DOI

10.12363/issn.1001-1986.23.07.0447

Recommended Citation

GAO Kui, WANG Youwei, QIAO Guodong, et al. (2024) "Mechanism and application of cross-interface fracturing for permeability enhancement through the roof blasting of tectonic coal seams," Coal Geology & Exploration: Vol. 52: Iss. 4, Article 5.
DOI: 10.12363/issn.1001-1986.23.07.0447
Available at: https://cge.researchcommons.org/journal/vol52/iss4/5

Reference

[1] ZHAO Tongbin,GUO Weiyao,TAN Yunliang,et al. Case studies of rock bursts under complicated geological conditions during multi–seam mining at a depth of 800 m[J]. Rock Mechanics and Rock Engineering,2018,51(5):1539−1564.

[2] 程远平,雷杨. 构造煤和煤与瓦斯突出关系的研究[J]. 煤炭学报,2021,46(1):180−198

CHENG Yuanping,LEI Yang. Causality between tectonic coal and coal and gas outbursts[J]. Journal of China Goal Society,2021,46(1):180−198

[3] 樊世星. 液态CO₂压裂煤岩增透及裂缝形成机制研究[J]. 岩石力学与工程学报,2021,40(8):1728

FAN Shixing. Study on the mechanism of fractures propagation and permeability enhancements induced by liquid CO₂ fracturing[J]. Chinese Journal of Rock Mechanics and Engineering,2021,40(8):1728

[4] XIA Binwei,LIU Xianfeng,SONG Dazhao,et al. Evaluation of liquid CO₂ phase change fracturing effect on coal using fractal theory[J]. Fuel,2021,287:119569.

[5] XU Jizhao,ZHAI Cheng,LIU Shimin,et al. Investigation of temperature effects from liquid CO₂ with different cycle parameters on the coal pore variation based on infrared thermal imagery and low–field nuclear magnetic resonance[J]. Fuel,2018,215(3):528−540.

[6] TENG Teng,XUE Yi,ZHANG Cun. Modeling and simulation on heat–injection enhanced coal seam gas recovery with experimentally validated non–Darcy gas flow[J]. Journal of Petroleum Science and Engineering,2019,177:734−744.

[7] ZHOU Lijun,ZHOU Xihua,FAN Chaojun,et al. Coal permeability evolution triggered by variable injection parameters during gas mixture enhanced methane recovery[J]. Energy,2022,252:124065.

[8] ZHI Sheng,ELSWORTH D,WANG Jiehao,et al. Hydraulic fracturing for improved nutrient delivery in microbially–enhanced coalbed–methane (MECBM) production[J]. Journal of Natural Gas Science and Engineering,2018,60:294−311.

[9] PANDEY R,HARPALANI S. An imaging and fractal approach towards understanding reservoir scale changes in coal due to bioconversion[J]. Fuel,2018,230:282−297.

[10] 卢义玉,柴成娟,周哲,等. 生物转化对煤层孔隙渗透性质的影响[J]. 采矿与安全工程学报,2021,38(1):165−172

LU Yiyu,CHAI Chengjuan,ZHOU Zhe,et al. Influence of bioconversion on pore permeability of coal seams[J]. Journal of Mining & Safety Engineering,2021,38(1):165−172

[11] 周宏伟,刘泽霖,孙晓彤,等. 深部煤体注水过程中渗流通道演化特征[J]. 煤炭学报,2021,46(3):867−875

ZHOU Hongwei,LIU Zelin,SUN Xiaotong,et al. Evolution characteristics of seepage channel during water infusion in deep coal samples[J]. Journal of China Coal Society,2021,46(3):867−875

[12] 王新丰,刘文港,王龙,等. 静态致裂作用下低渗厚煤层瓦斯增透数值模拟研究[J]. 煤田地质与勘探,2023,51(11):1−12

WANG Xinfeng,LIU Wengang,WANG Long,et al. Numerical simulations of enhancing permeability and gas extraction of thick coal seams through static fracturing[J]. Coal Geology & Exploration,2023,51(11):1−12

[13] NIU Xingang,PANG Dongdong,LIU Huihui,et al. Gas extraction mechanism and effect of ultra–high–pressure hydraulic slotting technology:A case study in Renlou Coal Mine[J]. Natural Resources Research,2023,32(1):321−339.

[14] 曹佐勇,王恩元,何学秋,等. 近距离突出煤层群水力冲孔卸压瓦斯抽采及效果评价研究[J]. 采矿与安全工程学报,2021,38(3):634−642

CAO Zuoyong,WANG Enyuan,HE Xueqiu,et al. Effect evaluation of pressure relief and gas drainage of hydraulic punching in short–distance coal seam group with the risk of outburst[J]. Journal of Mining & Safety Engineering,2021,38(3):634−642

[15] CHEN Dongdong,HE Wenrui,XIE Shengrong,et al. Increased permeability and coal and gas outburst prevention using hydraulic flushing technology with cross–seam borehole[J]. Journal of Natural Gas Science and Engineering,2020,73:103067.

[16] WANG Shen,LI Huamin,LI Dongyin. Numerical simulation of hydraulic fracture propagation in coal seams with discontinuous natural fracture networks[J]. Processes,2018,6(8):113.

[17] 李全贵,邓羿泽,胡千庭,等. 煤岩水力压裂物理试验研究综述及展望[J]. 煤炭科学技术,2022,50(12):62−72

LI Quangui,DENG Yize,HU Qianting,et al. Review and prospect of coal rock hydraulic fracturing physical experimental research[J]. Coal Science and Technology,2022,50(12):62−72

[18] 龚敏,刘万波,王德胜,等. 提高煤矿瓦斯抽放效果的控制爆破技术[J]. 北京科技大学学报,2006,28(3):223−226

GONG Min,LIU Wanbo,WANG Desheng,et al. Controlled blasting technique to improve gas pre–drainage effect in a coal mine[J]. Journal of University of Science and Technology Beijing,2006,28(3):223−226

[19] QIAO Guodong,LIU Zegong,YI Changping,et al. Quantitative assessment of the effect of in–situ stresses on blast–induced damage to rock[J]. Computers & Structures,2023,287:107116.

[20] 杨威,贾茹,李希建,等. 采煤工作面“爆注”一体化防突理论与技术[J]. 中国矿业大学学报,2021,50(4):764−775

YANG Wei,JIA Ru,LI Xijian,et al. Theory and technology of “blasting injection” integrated outburst prevention in coal face[J]. Journal of China University of Mining & Technology,2021,50(4):764−775

[21] 刘健,刘泽功,高魁,等. 不同装药模式爆破载荷作用下煤层裂隙扩展特征试验研究[J]. 岩石力学与工程学报,2016,35(4):735−742

LIU Jian,LIU Zegong,GAO Kui,et al. Experimental study of extension characters of cracks in coal seam under blasting load with different charging modes[J]. Chinese Journal of Rock Mechanics and Engineering,2016,35(4):735−742

[22] 郭德勇,张超,李柯,等. 松软低透煤层深孔微差聚能爆破致裂机理[J]. 煤炭学报,2021,46(8):2583−2592

GUO Deyong,ZHANG Chao,LI Ke,et al. Mechanism of millisecond–delay detonation on coal cracking under deep–hole cumulative blasting in soft and low permeability coal seam[J]. Journal of China Coal Society,2021,46(8):2583−2592

[23] LOU Zhen,WANG Kai,ZANG Jie,et al. Effects of permeability anisotropy on coal mine methane drainage performance[J]. Journal of Natural Gas Science and Engineering,2021,86(1):103733.

[24] GONG Shuang,TAN Yi,LIU Yunpeng,et al. Application of presplitting blasting technology in surrounding rock control of gob–side entry retaining with hard roof:A case study[J]. Advances in Materials Science and Engineering,2021,2021:1318975.

[25] 温颖远,郭志刚,曹安业,等. 基于微震数据评价的顶板深孔爆破卸压效果分析[J]. 煤炭科学技术,2020,48(6):57−63

WEN Yingyuan,GUO Zhigang,CAO Anye,et al. Analysis of pressure relief effect of roof deep hole blasting parameters based on micro–seismic data evaluation[J]. Coal Science and Technology,2020,48(6):57−63

[26] TU Min,ZHAO Gaoming,ZHANG Xiangyang,et al. Fracture evolution between blasting roof cutting holes in a mining stress environment[J]. Minerals,2022,12(4):418.

[27] 赵善坤. 深孔顶板预裂爆破与定向水压致裂防冲适用性对比分析[J]. 采矿与安全工程学报,2021,38(4):706−719

ZHAO Shankun. A comparative analysis of deep hole roof pre–blasting and directional hydraulic fracture for rockburst control[J]. Journal of Mining & Safety Engineering,2021,38(4):706−719

[28] 龚敏,王华,文斌. 岩石深孔爆破对邻近煤层的动应力作用[J]. 爆炸与冲击,2012,32(2):196−202

GONG Min,WANG Hua,WEN Bin. Dynamic stress in adjacent coal seams induced by deep–hole blasting in rock[J]. Explosion and Shock Waves,2012,32(2):196−202

[29] 龚敏,张凤舞,文斌,等. 煤巷底板岩石爆破提高瓦斯抽放率的应用与数值模拟[J]. 煤炭学报,2012,37(6):972−977

GONG Min,ZHANG Fengwu,WEN Bin,et al. Numerical simulation and application on blasting to improve gas drainage rate in floor rock of coal roadway[J]. Journal of China Coal Society,2012,37(6):972−977

[30] 穆朝民,齐娟. 爆炸荷载作用下煤体裂纹扩展机理模型实验研究[J]. 振动与冲击,2012,31(13):58−61

MU Chaomin,QI Juan. Model investigation on cracks propagation in coal under blast loading[J]. Journal of Vibration and Shock,2012,31(13):58−61

[31] 邓军,王津睿,任帅京,等. 声波探测技术在矿井领域中的应用及展望[J]. 煤田地质与勘探,2023,51(6):149−162

DENG Jun,WANG Jinrui,REN Shuaijing,et al. Application and prospect of acoustic detection in the mining sector[J]. Coal Geology & Exploration,2023,51(6):149−162