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.

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 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 Directional Hydraulic Fracturing (DHF) of the Roof, as an Element of Rock Burst Prevention in the Light of Underground Observations and Numerical Modelling

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 562
Author(s):  
Marek Jendryś ◽  
Andrzej Hadam ◽  
Mateusz Ćwiękała
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Seismic Activity ◽  
Black Coal ◽  
Directional Hydraulic Fracturing ◽  
Before And After ◽  
The Face

The following article analyzes the effectiveness of directional hydraulic fracturing (DHF) as a method of rock burst prevention, used in black coal mining with a longwall system. In order to define changes in seismic activity due to DHF at the “Rydułtowy” Black Coal Mine (Upper Silesia, Poland), observations were made regarding the seismic activity of the rock mass during coal mining with a longwall system using roof layers collapse. The seismic activity was recorded in the area of the longwall itself, where, on a part of the runway, the rock mass was expanded before the face of the wall by interrupting the continuity of the rock layers using DHF. The following article presents measurements in the form of the number and the shock energy in the area of the observed longwall, which took place before and after the use of DHF. The second part of the article unveils the results of numerical modeling using the discrete element method, allowing to track the formation of goafs for the variant that does not take DHF into consideration, as well as with modeled fractures tracing DHF carried out in accordance with the technology used at “Rydułtowy” coal mine.

Permeability Improvement Technology of Directional Hydraulic Fracturing in Low Permeability

2014 ◽  
Vol 599-601 ◽  
pp. 385-390 ◽  
Author(s):  
Xue Xi Chen ◽  
Rui Qing Bi ◽  
Wen Guang Jin ◽  
Yong Xu
Keyword(s):  
Stress Concentration ◽  
Hydraulic Fracturing ◽  
Maximum Concentration ◽  
Local Stress ◽  
Field Application ◽  
Low Permeability ◽  
Pressure Relief ◽  
Local Stress Concentration ◽  
Directional Hydraulic Fracturing ◽  
Better Than

According to the conventional fracturing could easily lead to the local stress concentration of coal, the effect of pressure relief and permeability improvement is not ideal. The mechanism of directional hydraulic fracturing is analyzed and the parameters such as the layout of directional hole, the fracturing hole sealing, the minimum cracking pressure are discussed, then the field application tests are carried out. The results show that the directional hydraulic fracturing effect is better than that of ordinary fracturing hole and the maximum concentration and the average drainage scalar is respectively 3.75 times and 4 times of the ordinary hole pumping gas fracturing effects. The effect of permeability improvement is remarkable.

scholarly journals Analysis and Application on Controlling Thick Hard Roof Caving with Deep-Hole Position Presplitting Blasting

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Baobao Chen ◽  
Changyou Liu
Keyword(s):  
Large Scale ◽  
Mining Area ◽  
Field Application ◽  
Deep Hole ◽  
Mining Operations ◽  
Hard Roof ◽  
Measurement Analysis ◽  
Mining Safety ◽  
Strata Behavior ◽  
Working Resistance

For the thick hard roof (THR) in Datong mining area, mining operations often led to large-scale hanging-roof and frequent and strong strata behavior, threatening mining safety seriously. Based on the instability mechanism, the fracture model for THR was established, including rock blocks articulation and combined cantilever beam, and the limit initial and periodic intervals of THR were determined to be 36.0 m and 8.0 m, respectively. The study proposed the deep-hole presplitting blasting (DPB) for weakening THR for mitigating strong strata behaviors. Blasting-induced fracture characteristics were calculated, determining the charging coefficient and holes spacing. LS-DYNA was employed for establishing a DPB model to analyze crack evolution under the synergistic action of blasting stress wave and detonation gas and the attenuation characteristics for rock peak particle velocity, verifying the rationality of blasting parameters. Field measurement analysis indicated that the immediate roof induced a timely collapse to fill the goaf and the THR was effectively cut off near the presplitting line. Meanwhile, the working resistance was utilized with safety allowance. The field application showed the DPB on controlled THR caving achieved the significant effect.

scholarly journals Directional hydraulic fracturing technology for prefabricated longitudinal guide seams in a coal mine tight sandstone roof

2021 ◽  
pp. 014459872110289
Author(s):  
Liangwei Li ◽  
Wenbin Wu
Keyword(s):  
Acoustic Emission ◽  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Tight Sandstone ◽  
Directional Hydraulic Fracturing ◽  
Working Face ◽  
Secondary Cracks ◽  
Initiation Pressure ◽  
Multi Level ◽  
Fracturing Experiments

Triaxial hydraulic fracturing experiments were used to study the initiation pressure variation and acoustic emission characteristics of different guide seams sizes during roof hydraulic fracturing. Numerical simulations were used to explore the feasibility of multiple boreholes with prefabricated guide seams. An experiment of hydraulic fracturing on a pillar-free working face was also carried out in a coal mine. The results show that the specimens with guide seams reduced the initiation pressure, with the number of acoustic emission events and initiation pressure being inversely proportional to the size of the guide seams. Specimens without guide seams were deflected by stress and produced multi-level cracks, while the specimens with guide seams did not produce large secondary cracks and deflection. When the stress difference was small, three holes penetrated but not under large stress differences. The hydraulic fracturing technology of prefabricated longitudinal guide seams was tested in the Ningtiaota Coal Mine, and the auxiliary transportation roadway of S1201 working face was successfully retained for reuse in adjacent working faces.

scholarly journals Evaluation Method of the Vertical Well Hydraulic Fracturing Effect Based on Production Data

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Debin Xia ◽  
Zhengming Yang ◽  
Daolun Li ◽  
Yapu Zhang ◽  
Ying He ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Optimization Design ◽  
Large Scale ◽  
Evaluation Method ◽  
Outer Region ◽  
Fracture Network ◽  
Single Fracture ◽  
Vertical Well ◽  
Cumulative Production ◽  
Volumetric Fracturing

Hydraulic fracturing technology has become a key technology for the development of low-permeability/tight oil and gas reservoirs. The evaluation on the postfracturing effect is imperative to the formulation and implementation of the fracturing and development plan. Based on the characteristics of the flow in fracture network after a large-scale hydraulic fracturing, a numerical method for evaluating the effect of fracturing in vertical well was established. This study conducts postfracturing effect evaluations to block C Oilfield’s wells that underwent conventional fracturing and volumetric fracturing, respectively, proposes the definition of fracture network conductivity and its relationship with cumulative production, and analyzes the fracturing construction parameters. The results suggest that the conventional fracturing can only form a single fracture instead of a stimulated reservoir volume (SRV) region. However, the volumetric fracturing transformation can form a complex fracture network system and SRV region and meanwhile bring obvious increase in the production. The effective time lasts for a longer period, and the increase of average daily oil is 2.2 times more than that of conventional fracturing. Additionally, with the progress of the production, the SRV area within the core region of the volume transformation gradually decreased from 6664.84 m2 to 4414.45 m2; the SRV area of the outer region decreased from 7913.5 m2 to 5391.3 m2. As the progress develops, the equivalent permeability and the area of the fracture gradually decrease as the fracturing effect gradually weakens, and so does the conductivity of the network decreasing exponentially; a good correlation is observed between the conductivity of the fracture network, the cumulative production, and fracturing construction parameters, which can serve as the evaluation parameters for the fracturing effects and the basis for fracturing productivity prediction and provide a guidance for fracturing optimization design.

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.

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