Study on the surface crack propagation mechanism of coal and sandstone subjected to cryogenic cooling with liquid nitrogen

被引:43
作者
Du, Menglin [1 ]
Gao, Feng [1 ,2 ]
Cai, Chengzheng [2 ]
Su, Shanjie [2 ]
Wang, Zekai [2 ]
机构
[1] China Univ Min & Technol, Sch Mech & Civil Engn, Xuzhou 221116, Jiangsu, Peoples R China
[2] China Univ Min & Technol, State Key Lab Geomech & Deep Underground Engn, Xuzou 221116, Peoples R China
基金
中国博士后科学基金; 中国国家自然科学基金;
关键词
Liquid nitrogen fracturing; Crack propagation mechanism; Ultrasound detection analyser; Scanning electron microscopy; Damage; WATERLESS FRACTURING TECHNOLOGIES; DAMAGE; GRANITE; FLUID; MODEL; WELL;
D O I
10.1016/j.jngse.2020.103436
中图分类号
TE [石油、天然气工业]; TK [能源与动力工程];
学科分类号
0807 ; 0820 ;
摘要
Conventional hydraulic fracturing often causes problems such as reservoir damage, water consumption, and pollution. Recently, liquid nitrogen (LN2) fracturing, an environmentally friendly fracturing technology, has attracted more attention. In this paper, the mechanism of surface crack propagation in coal and sandstone induced by LN2 is explored through laboratory tests and numerical simulations. An ultrasound detection analyser is employed to investigate the longitudinal wave velocity (V-p) changes in specimens before and after LN2 cooling. The micromorphology of specimens is observed through scanning electron microscopy (SEM). Furthermore, the heat transfer characteristics and damage zone of specimens induced by LN2 are determined. The experimental results indicate that LN2 cooling is more effective for improving coal permeability than it is for improving sandstone permeability. After LN2 cooling, a complex fracture network is observed from the coal surface. However, limited damage to the sandstone surface is observed. V-p decreases by 24.7%-38.1% for coal specimens after cooling but by less than 0.06% for sandstone. The simulation results indicate that the low-temperature region and the tensile area gradually expand into the interior of the specimens with time. However, the temperature of sandstone drops faster than coal when specimens contact LN2. The maximum tensile stress induced by the instantaneous contact between the specimens and LN2 can be generated at the outer surface of the specimens. Moreover, the maximum damage area of coal extends 3.3 mm from the outer surface, while the damage zone of the sandstone is almost zero.
引用
收藏
页数:10
相关论文
共 39 条
[1]   Evaluation of coal damage and cracking characteristics due to liquid nitrogen cooling on the basis of the energy evolution laws [J].
Cai, Chengzheng ;
Gao, Feng ;
Li, Gensheng ;
Huang, Zhongwei ;
Hou, Peng .
JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING, 2016, 29 :30-36
[2]   Experimental study of the effect of liquid nitrogen cooling on rock pore structure [J].
Cai, Chengzheng ;
Li, Gensheng ;
Huang, Zhongwei ;
Shen, Zhonghou ;
Tian, Shouceng ;
Wei, Jiangwei .
JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING, 2014, 21 :507-517
[3]   Rock Pore Structure Damage Due to Freeze During Liquid Nitrogen Fracturing [J].
Cai, Chengzheng ;
Li, Gensheng ;
Huang, Zhongwei ;
Shen, Zhonghou ;
Tian, Shouceng .
ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING, 2014, 39 (12) :9249-9257
[4]   Laboratory system for studying cryogenic thermal rock fracturing for well stimulation [J].
Cha, Minsu ;
Alqahtani, Naif B. ;
Yin, Xiaolong ;
Kneafsey, Timothy J. ;
Yao, Bowen ;
Wu, Yu-Shu .
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, 2017, 156 :780-789
[5]   Cryogenic fracturing for reservoir stimulation - Laboratory studies [J].
Cha, Minsu ;
Yin, Xiaolong ;
Kneafsey, Timothy ;
Johanson, Brent ;
Alqahtani, Naif ;
Miskimins, Jennifer ;
Patterson, Taylor ;
Wu, Yu-Shu .
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, 2014, 124 :436-450
[6]  
[褚召祥 Chu Zhaoxiang], 2016, [煤田地质与勘探, Coal Geology & Exploration], V44, P37
[7]  
COMSOL, 2016, Structural Mechanics Module User's Guide
[8]  
Cui Y., 2017, STUDY CORRELATION HE
[9]  
Grundmann S.R., 1998, SPE E REGIONAL M
[10]   Influence of liquid nitrogen cryotherapy on mechanic properties of coal and constitutive model study [J].
Jin, Xiaomin ;
Gao, Jianliang ;
Su, Chengdong ;
Liu, Jiajia .
ENERGY SOURCES PART A-RECOVERY UTILIZATION AND ENVIRONMENTAL EFFECTS, 2019, 41 (19) :2364-2376