Open AccessThe propagation research of hydraulically created fractures in coal seams based on discrete element method
Author(s) -
Yanjun Lü,
Jianchao Han,
V. V. Shelepov,
Qiang Wang,
Zhu Yuanlin,
Jianchun Guo,
Liang Zhang,
Wei Han
Publication year - 2019
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.179
H-Index - 26
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/384/1/012013
Subject(s) - hydraulic fracturing , coal , fracture (geology) , petroleum engineering , coalbed methane , geology , geotechnical engineering , fracturing fluid , coal mining , viscosity , hydraulic fluid , well stimulation , materials science , engineering , hydraulic machinery , mechanical engineering , composite material , petroleum , reservoir engineering , waste management , paleontology
Coalbed methane (CBM) is clean unconventional energy that can be exploited with stimulation treatment to realize commercial value, and hydraulic fracturing is the key technology for increasing CBM production. The simulation of hydraulic fractures is an important research content that can guide the engineering practice to achieve the purpose of increasing production. Based on the distribution characteristic of cleats in coal, the research on the propagation of hydraulic fractures is carried out via Discrete element method (DEM). The simulated results show that: hydraulic fractures mainly propagate along the cleats towards the maximum principal stress. The fracture network can be formed due to the intersection of face cleats and butt cleats that can propagate at certain pressure. During the injection process of fracturing fluid, the pressure at injection point decreases with the fracture propagation until the pressure tends to be stable. With the increase of injection rate and fracturing fluid viscosity at the same condition, the maximum aperture of hydraulic fracture increases, while the length of principal hydraulic fracture shortens. Therefore, to achieve the purpose of forming hydraulic fracture network in coal seams with cleats, low viscosity fracturing fluid and low injection rate need be applied to the fracturing technology. As the cleat density increases, the number of branch fractures increases, but the length of principal hydraulic fracture becomes short. Long and narrow hydraulic fractures are easily formed in coal seams with lower cleat density.