scholarly journals The methodology for working out the techniques for geophysical monitoring of the process of directional hydraulic fracturing of a hard roof and the process of local hydrotreating of a coal seam face working space, its implementation within the framework of RSF project

2018 ◽  
Vol 206 ◽  
pp. 012022
Author(s):  
A V Shadrin ◽  
V I Klishin
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Geophysical Monitoring ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof ◽  
Working Space ◽  
Working Out

scholarly journals Fully Coupled Multi-Scale Model for Gas Extraction from Coal Seam Stimulated by Directional Hydraulic Fracturing

2019 ◽  
Vol 9 (21) ◽  
pp. 4720 ◽  
Author(s):  
Ge ◽  
Zhang ◽  
Sun ◽  
Hu
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Scale Model ◽  
Gas Extraction ◽  
Coal Seams ◽  
Directional Hydraulic Fracturing ◽  
Coal Mine Methane ◽  
Multi Scale ◽  
Fully Coupled

Although numerous studies have tried to explain the mechanism of directional hydraulic fracturing in a coal seam, few of them have been conducted on gas migration stimulated by directional hydraulic fracturing during coal mine methane extraction. In this study, a fully coupled multi-scale model to stimulate gas extraction from a coal seam stimulated by directional hydraulic fracturing was developed and calculated by a finite element approach. The model considers gas flow and heat transfer within the hydraulic fractures, the coal matrix, and cleat system, and it accounts for coal deformation. The model was verified using gas amount data from the NO.8 coal seam at Fengchun mine, Chongqing, Southwest China. Model simulation results show that slots and hydraulic fracture can expand the area of gas pressure drop and decrease the time needed to complete the extraction. The evolution of hydraulic fracture apertures and permeability in coal seams is greatly influenced by the effective stress and coal matrix deformation. A series of sensitivity analyses were performed to investigate the impacts of key factors on gas extraction time of completion. The study shows that hydraulic fracture aperture and the cleat permeability of coal seams play crucial roles in gas extraction from a coal seam stimulated by directional hydraulic fracturing. In addition, the reasonable arrangement of directional boreholes could improve the gas extraction efficiency. A large coal seam dip angle and high temperature help to enhance coal mine methane extraction from the coal seam.

Field investigation into directional hydraulic fracturing for hard roof in Tashan Coal Mine

2013 ◽  
Vol 19 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Bing-Xiang Huang ◽  
Bin Yu ◽  
Feng Feng ◽  
Zhao Li ◽  
You-Zhuang Wang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Field Investigation ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof

scholarly journals Development status and Prospect of directional hydraulic fracturing technology for coal mine roof

2020 ◽  
Vol 194 ◽  
pp. 01043
Author(s):  
LI Liangwei
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Large Scale ◽  
Evaluation Method ◽  
Field Application ◽  
Control Technology ◽  
Control Methods ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof ◽  
Extension Mechanism

Aiming at the harm and control methods of thick and hard roof in coal mine, the paper firstly analyzes the advanced control methods of thick and hard roof, such as directional shaped charge blasting roof control technology, hydraulic fracturing roof control technology, abrasive water jet directional cutting roof technology, large-scale special roof cutting machine, etc Control hole fracturing, transverse slotting fracturing and longitudinal slotting fracturing are compared and analyzed; finally, the shortcomings of current research are analyzed. According to the current research results, the analysis shows that: the method of controlling roof by blasting in the future will be limited, while the method of hydraulic fracturing, especially directional hydraulic fracturing, has obvious advantages; the longitudinal slotting fracturing has the best control over fractures in the directional hydraulic fracturing technology; the guiding mechanism and fracture extension mechanism of longitudinal slotting hydraulic fracturing in thick and hard roof need to be further studied; lack of field application research and corresponding equipment development, lack of field effect evaluation method after longitudinal slotting fracturing.

scholarly journals Determination of fracture location of double-sided directional fracturing pressure relief for hard roof of large upper goaf-side coal pillars

2019 ◽  
Vol 38 (1) ◽  
pp. 111-136 ◽  
Author(s):  
Jiangwei Liu ◽  
Changyou Liu ◽  
Xuehua Li
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mine ◽  
High Stress ◽  
Coal Pillar ◽  
Local Stress ◽  
Pressure Relief ◽  
Directional Hydraulic Fracturing ◽  
Fracture Location ◽  
Hard Roof ◽  
Coal Pillars

After mining the upper-goaf side, large coal pillars and part of hard roof exposed above the pillars remain. The hard roof can significantly deform the roadway by transferring high stress through coal pillars to the roadway. This paper reports the use of hydraulic fracturing technology to cut the hard roof on both sides (i.e. the broken roof slides to the goaf) to relieve the pressure. The position of the roof fracture is the key to controlling the pressure relief. The bearing characteristics of the large coal pillars and hard roof are analyzed to establish a mechanical model of the broken-roof sliding instability after directional fracturing and determine the width of the coal pillars that can collapse under maximum overburden load on coal pillars as a reasonable hydraulic fracturing position. The results show that the distance from the mine gateway to the fracture location increases with increasing hard-roof length, coal pillar depth, coal pillar thickness (mining height), and goaf width. In addition, the distance to the mine gateway decreases with increasing coal strength, support of the coal pillar by the anchor rod, cohesive force, and internal friction angle of the coal–rock interface. Engineering tests were applied in coal roadway 5107 of coal seam 5# of the Baidong Coal Mine of the Datong Coal Mine Group. Given the site conditions, a reasonable fracturing length of 8.8 m was obtained. Next, directional hydraulic fracturing was implemented. The comparison of the roof deformation before and after fracturing suggests that this method reduces the local stress concentration in coal pillars, which allows the surrounding rock deformation in roadway 5107 to be controlled.

scholarly journals Geophysical and geo-mechanical methods for estimating roof directional hydraulic fracturing works

2021 ◽  
Vol 330 ◽  
pp. 01001
Author(s):  
Vladimir Klishin ◽  
Gleb Opruk ◽  
Alexaner Teleguz
Keyword(s):  
Hydraulic Fracturing ◽  
Experimental Testing ◽  
Physical Methods ◽  
Mine Site ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof ◽  
Transmitted Waves ◽  
Mechanical Methods ◽  
Testing Data ◽  
Method Of Extraction

Directional hydraulic fracturing method (DHF method) for controlling hard roof in coal mines and the means of its implementation is given in the paper. The method allows getting extended, set in a given direction cracks for stratification and cutting off the roof and for providing their controlled caving in different technological schemes. Geo-physical methods are introduced, the monitoring and the mine site experimental testing data on controlling the roofs applying the method of extraction pillar seismic testing on transmitted waves are studied. The experience of applying the method at Kuzbass mines are analyzed.

Directional hydraulic fracturing to control hard-roof rockburst in coal mines

2012 ◽  
Vol 22 (2) ◽  
pp. 177-181 ◽  
Author(s):  
Jun Fan ◽  
Linming Dou ◽  
Hu He ◽  
Taotao Du ◽  
Shibin Zhang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Mines ◽  
Directional Hydraulic Fracturing ◽  
Hard Roof

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

2021 ◽  
Vol 11 (9) ◽  
pp. 4125
Author(s):  
Zhe Xiang ◽  
Nong Zhang ◽  
Zhengzheng Xie ◽  
Feng Guo ◽  
Chenghao Zhang
Keyword(s):  
Coal Seam ◽  
Cooperative Control ◽  
Field Tests ◽  
Surrounding Rock ◽  
Deep Hole ◽  
Coal Seams ◽  
Thick Coal Seam ◽  
Structure Damage ◽  
Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

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