Research on hydraulic fracturing technology and equipment of directional long drilling with sand in coal seam roof

Authors

ZHANG Jian, Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp., Xi’an 710077, ChinaFollow
LIU Le, Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp., Xi’an 710077, ChinaFollow
ZHAO Jizhan, Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp., Xi’an 710077, China
SUN Siqing, Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp., Xi’an 710077, China
WANG Chenyang, Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp., Xi’an 710077, China

Abstract

Due to low permeability, fast gas-rate decline, uneven fracturing, easy fracture closure, it is difficult to perform advance gas extraction in broken-soft coal seams. Aimed at these issues, this study has been proposed a new idea to enhance the coalbed permeability and eventually the gas extraction, which is based on roof-supporting, long-reach directional drilling, and hydraulic fracturing. Corresponding equipment including fracturing pump unit, directional sandblasting perforation assembly, sand control packer and tools have been developed. Specifically, the pumping unit is capable of a pumping rate up to 90 m³/h, a pumping pressure up to 70 MPa, and a proppant concentration up to 20%, and a proppant particle size up to 1 mm; The directional sandblasting perforation assembly is driven by hydraulic pressure, with a maximum rotation angle of 180°; And the sand control packer can uphold up to 70 MPa with a maximum expansion factor of 2. In addition, we applied such technologies as long-reach directional drilling, continuous sandblasting perforation, and multistage hydraulic fracturing to a field pilot test in Xinjing coal mine, Yangquan, Shanxi Province. A total of 80 directional sandblasting shots at a pressure of 22.6-28.6 MPa, and 16 fracturing stages were carried out in two boreholes at an average depth of 609 m. And 19.8 t silica sand (a concentration of 2-3 vol.%), 2808.5 m³ fracturing fluid (153.8-235.1 m³ for a single fracturing stage), and 36.47 t walnut shell (a concentration of 2.02%-2.56%) were injected. The tests achieved a fracture half-length of 20-38 m in estimation, and average gas rates of 1025 and 2811 m³/d in 100 days after the treatment. Besides, it is found that the fracturing equipment has a large sand injection capacity, high pumping rate, and continuous operation. The coal seam permeability was significantly enhanced after fracturing, which led to great improvement in gas concentration and purity. This research provide new ideas for permeability enhancement in broken-soft coal seams and serves as a good reference for advance treatment in similar mining areas in China.

Keywords

staged sand fracturing, roof directional long drilling, directional sand blasting perforation device, hydraulic sand fracturing pump set, directional sand blasting perforation

DOI

10.12363/issn.1001-1986.22.03.0201

Recommended Citation

ZHANG Jian, LIU Le, ZHAO Jizhan, et al. (2022) "Research on hydraulic fracturing technology and equipment of directional long drilling with sand in coal seam roof," Coal Geology & Exploration: Vol. 50: Iss. 8, Article 5.
DOI: 10.12363/issn.1001-1986.22.03.0201
Available at: https://cge.researchcommons.org/journal/vol50/iss8/5

Reference

[1] 申宝宏,刘见中,张泓. 我国煤矿瓦斯治理的技术对策[J]. 煤炭学报,2007,32(7):673−679. SHEN Baohong,LIU Jianzhong,ZHANG Hong. The technical measures of gas control in China coal mines[J]. Journal of China Coal Society,2007,32(7):673−679.

[2] 程远平,付建华,俞启香. 中国煤矿瓦斯抽采技术的发展[J]. 采矿与安全工程学报,2009,26(2):127−139. CHENG Yuanping,FU Jianhua,YU Qixiang. Development of gas extraction technology in coal mines of China[J]. Journal of Mining & Safety Engineering,2009,26(2):127−139.

[3] 李全贵,林柏泉,翟成,等. 煤层脉动水力压裂中脉动参量作用特性的实验研究[J]. 煤炭学报,2013,38(7):1185−1190. LI Quangui,LIN Baiquan,ZHAI Cheng,et al. Experimental study on action characteristic of pulsating parameters in coal seam pulse hydraulic fracturing[J]. Journal of China Coal Society,2013,38(7):1185−1190.

[4] 曾义金,周俊,王海涛,等. 深层页岩真三轴变排量水力压裂物理模拟研究[J]. 岩石力学与工程学报,2019,38(9):1758−1766. ZENG Yijin,ZHOU Jun,WANG Haitao,et al. Research on true triaxial hydraulic fracturing in deep shale with varying pumping rates[J]. Chinese Journal of Rock Mechanics and Engineering,2019,38(9):1758−1766.

[5] 李倩. 煤矿井下射流割缝复合压裂增透机理及试验研究[D]. 重庆：重庆大学，2019.

LI Qian. The mechanism and application of composite fracturing with hydraulic slotting for permeability enhancement in underground coal mine[D]. Chongqing：Chongqing University，2019.

[6] 秦江涛,陈玉涛. 低透气性煤层高压水力压裂–冲孔联合增透技术研究及应用[J]. 矿业安全与环保,2021,48(6):53−57. QIN Jiangtao,CHEN Yutao. Research and application of combined antireflection technology of high pressure hydraulic fracturing and punching in low permeability coal seam[J]. Mining Safety & Environmental Protection,2021,48(6):53−57.

[7] 牟全斌,闫志铭,张俭. 煤矿井下定向长钻孔水力压裂瓦斯高效抽采技术[J]. 煤炭科学技术,2020,48(7):296−303. MOU Quanbin,YAN Zhiming,ZHANG Jian. High efficiency gas drainage technology of hydraulic fracturing with directional long drilling in underground coal mine[J]. Coal Science and Technology,2020,48(7):296−303.

[8] 陈冬冬,孙四清,张俭,等. 井下定向长钻孔水力压裂煤层增透技术体系与工程实践[J]. 煤炭科学技术,2020,48(10):84−89. CHEN Dongdong,SUN Siqing,ZHANG Jian,et al. Technical system and engineering practice of coal seam permeability improvement through underground directional long borehole hydraulic fracturing[J]. Coal Science and Technology,2020,48(10):84−89.

[9] 王选琳,李鹏,周东平,等. 煤矿井下水力加砂压裂技术工程应用研究[J]. 河南城建学院学报,2020,29(3):29−37. WANG Xuanlin,LI Peng,ZHOU Dongping,et al. Engineering application of hydraulic sand fracturing technology in coal mine[J]. Journal of Henan University of Urban Construction,2020,29(3):29−37.

[10] HU Qianting,LIU Le,LI Quangui,et al. Experimental investigation on crack competitive extension during hydraulic fracturing in coal measures strata[J]. Fuel,2020,265:117003.

[11] 冯仁俊. 煤层群分层水力压裂与多层综合压裂增透效果对比研究[J]. 煤矿安全,2021,52(12):21−28. FENG Renjun. Comparative study on permeability enhancement effect of separate–layer fracturing and multi–layers comprehensive fracturing in coal seam group[J]. Safety in Coal Mines,2021,52(12):21−28.

[12] 王晓光. 煤层水力压裂应力演化机制及应用研究[D]. 重庆：重庆大学，2019.

WANG Xiaoguang. Research on evolution mechanism and application of coal seam stress during hydraulic fracturing[D]. Chongqing：Chongqing University，2019.

[13] JIANG Zhizhong,LI Quangui,HU Qianting,et al. Underground microseismic monitoring of a hydraulic fracturing operation for CBM reservoirs in a coal mine[J]. Energy Science and Engineering,2019,7(3):986−999.

[14] 范涛. 基于钻孔瞬变电磁的煤层气压裂效果检测方法[J]. 煤炭学报,2020,45(9):3195−3207. FAN Tao. Coalbed methane fracturing effectiveness test using bore–hole transient electromagnetic method[J]. Journal of China Coal Society,2020,45(9):3195−3207.

[15] 王褀. 大湾煤矿穿层钻孔水力压裂技术的示范性研究及应用[J]. 煤矿安全,2016,47(7):155−159. WANG Qi. A Demonstrative research and application of hydraulic fracturing by crossing borehole in Dawan mine[J]. Safety in Coal Mines,2016,47(7):155−159.

[16] 陈建,贾秉义,董瑞刚,等. 煤矿井下水力压裂加骨料增透瓦斯抽采技术应用[J]. 煤炭工程,2021,53(2):90−94. CHEN Jian,JIA Bingyi,DONG Ruigang,et al. Application of hydraulic fracturing and aggregate injecting for permeability enhancement in underground coal mine gas extraction[J]. Coal Engineering,2021,53(2):90−94.

[17] 张群,葛春贵,李伟,等. 碎软低渗煤层顶板水平井分段压裂煤层气高效抽采模式[J]. 煤炭学报,2018,43(1):150−159. ZHANG Qun,GE Chungui,LI Wei,et al. A new model and application of coalbed methane high efficiency production from broken soft and low permeable coal seam by roof strata–in horizontal well and staged hydraulic fracture[J]. Journal of China Coal Society,2018,43(1):150−159.

[18] 孙四清,张群,闫志铭,等. 碎软低渗高突煤层井下长钻孔整体水力压裂增透工程实践[J]. 煤炭学报,2017,42(9):2337−2344. SUN Siqing,ZHANG Qun,YAN Zhiming,et al. Practice of permeability enhancement through overall hydraulic fracturing of long hole in outburst–prone soft crushed coal seam with low permeability[J]. Journal of China Coal Society,2017,42(9):2337−2344.

[19] 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. 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.

[20] 郑凯歌. 碎软低透煤层底板梳状长钻孔分段水力压裂增透技术研究[J]. 采矿与安全工程学报,2020,37(2):272−281. ZHENG Kaige. Permeability improving technology by sectional hydraulic fracturing for comb−like long drilling in floor of crushed and soft coal seam with low permeability[J]. Journal of Mining & Safety Engineering,2020,37(2):272−281.