scholarly journals RISK REDUCTION ESTIMATION FOR UNDERGROUND MINING OF GAS-CONTAINED COAL SEAMS WHILE USING THE HYDRAULIC FRACTURING

2019 ◽  
Vol 2 (5) ◽  
pp. 3-11
Author(s):  
Sergey Serdyukov ◽  
Tatiana Shilova ◽  
Leonid Rybalkin
Keyword(s):  
Comparative Analysis ◽  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Risk Reduction ◽  
Underground Mining ◽  
Coal Seams ◽  
Filtration Resistance ◽  
Different Types ◽  
Interval Hydraulic Fracturing ◽  
Preliminary Degassing

In the paper, influence of hydraulic fracturing parameters on filtration resistance of system of parallel holes during preliminary degassing of coal seam loaded with strata pressure is considered. Results of comparative analysis of degassing rates of coal seam while using holes without hydraulic fracturing and holes with non-directed or plural interval hydraulic fracturing of various orientation are represented. Estimation of influence of fracturing of different types on risk reduction of underground mining of gas-contained coal seams is given. Obtained results allow to estimate perspective of application of present modifications of hydraulic fracturing technology at coal mines.

Hydro-splitting of coal seams for their effective degassing preparation through underground wells

2020 ◽  
pp. 15-25
Author(s):  
S. V. Slastunov ◽  
A. V. Ponizov ◽  
A. P. Sadov ◽  
A. M.-B. Khautiev
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Underground Mining ◽  
Working Fluid ◽  
Coal Seams ◽  
Natural Systems ◽  
Zone Of Influence ◽  
Complex Technology ◽  
Improved Technology ◽  
Hydrodynamic Effects

The article is devoted to the issues of improving the complex technology of coal seam degassing based on its hydrodynamic treatment. The possible modes of implementation of the introduction of working fluid into the coal seam in the process of its injection through wells drilled from preparatory workings and specially sealed to a certain depth, which ensures minimization of breaks of working fluid into the mine. Studies have been carried out to optimize the main parameters of hydrodynamic effects. Rational values of the effective well length and injection volume are established. The expediency of achieving significant rates of injection of the working agent into the formation for the disclosure of natural systems of cracks in it is shown. The directions of increasing the efficiency of formation degassing are investigated. The effectiveness of the integrated reservoir degassing technology was evaluated based on the factors of increasing methane production from underground reservoir degassing wells drilled into the zone of influence of underground hydraulic fracturing wells, and the total methane removal over the entire period of reservoir degassing. The efficiency of improved technology of hydraulic fracturing in underground mining for factors reducing downtime pollution control equipment, gazoobilnosti stope and the productivity of coal mining in zones of intensive integrated reservoir degassing.

scholarly journals Stimulation of Gas Emission Processes in Boreholes Using Interval Hydraulic Fracturing in Borehole Local Parts

2018 ◽  
Vol 41 ◽  
pp. 03005 ◽  
Author(s):  
Vladimir Klishin ◽  
Gleb Opruk ◽  
Alexandr Tatsienko
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
High Speed ◽  
Mining Industry ◽  
Coal Seams ◽  
Strange Situation ◽  
Gas Barrier ◽  
Gas Drainage ◽  
Working Face ◽  
Interval Hydraulic Fracturing

Due to limited scope of degassing activities and insufficient efficiency of degassing schemes in many methane-rich Russian coal mines there is a gas barrier which prevents miners from achieving high speed at developing mine workings and high working face loads. For that reason there is a strange situation in coal-mining industry when technical capabilities of coal-face operation equipment working on gently sloping coal seams exceed ultimate face load in relation to gas factor several times. The authors prove the efficiency of using coal seam interval hydraulic fracturing for gas drainage stimulation. They consider the established coal seam gas drainage methods. The authors developed the process flowchart for coal seam hydraulic fracturing implementation and suggested using equipment for taking measures aimed at gas drainage stimulation.

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.

scholarly journals Investigation of Hydraulic Fracturing Crack Propagation Behavior in Multi-Layered Coal Seams

2020 ◽  
Vol 10 (3) ◽  
pp. 1153 ◽  
Author(s):  
Shirong Cao ◽  
Xiyuan Li ◽  
Zhe Zhou ◽  
Yingwei Wang ◽  
Hong Ding
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Crack Propagation ◽  
Principal Stress ◽  
Fracture Propagation ◽  
Clean Energy ◽  
Burial Depth ◽  
Coal Seams ◽  
Initiation Pressure ◽  
Dip Angle

Coalbed methane is not only a clean energy source, but also a major problem affecting the efficient production of coal mines. Hydraulic fracturing is an effective technology for enhancing the coal seam permeability to achieve the efficient extraction of methane. This study investigated the effect of a coal seam reservoir’s geological factors on the initiation pressure and fracture propagation. Through theoretical analysis, a multi-layered coal seam initiation pressure calculation model was established based on the broken failure criterion of maximum tensile stress theory. Laboratory experiments were carried out to investigate the effects of the coal seam stress and coal seam dip angle on the crack initiation pressure and fracture propagation. The results reveal that the multi-layered coal seam hydraulic fracturing initiation pressure did not change with the coal seam inclination when the burial depth was the same. When the dip angle was the same, the initiation pressure linearly increased with the reservoir depth. A three-dimensional model was established to simulate the actual hydraulic fracturing crack propagation in multi-layered coal seams. The results reveal that the hydraulic crack propagated along the direction of the maximum principal stress and opened in the direction of the minimum principal stress. As the burial depth of the reservoir increased, the width of the hydraulic crack also increased. This study can provide the theoretical foundation for the effective implementation of hydraulic fracturing in multi-layered coal seams.

scholarly journals Field Investigation of Hydraulic Fracturing in Coal Seams and Its Enhancement for Methane Extraction in the Southeast Sichuan Basin, China

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3451 ◽  
Author(s):  
Zuxun Zhang ◽  
Hongtu Wang ◽  
Bozhi Deng ◽  
Minghui Li ◽  
Dongming Zhang
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Sichuan Basin ◽  
High Stress ◽  
Fluid Pressure ◽  
Field Investigation ◽  
Stress Sensitivity ◽  
Extraction Rate ◽  
Coal Seams ◽  
Methane Extraction

Hydraulic fracturing is an effective technology for enhancing the extraction of reservoir methane, as proved by field experience and laboratory experiments. However, unlike conventional reservoirs, coal seams had high stress sensitivity and high anisotropy. Therefore, the efficiency of hydraulic fracturing in coal seams needs to be investigated. In this study, hydraulic fracturing was performed at Nantong mine in the southeast Sichuan basin, China. The field investigation indicated that the hydraulic fracturing could significantly enhance the methane extraction rate of boreholes ten times higher than that of normal boreholes in one of the minable coal seams (named #5 coal seam). The performance of hydraulic fracturing in three districts revealed that compared with south flank, the fluid pressure was higher and the injection rate was lower in north flank. The methane extraction rate of south flank was inferior to that of north flank. It indicated hydraulic fracturing had less effect on #5 coal seam in south flank. Moreover, the injection of high-pressure water in coal seams could also drive methane away from boreholes. The methane extraction rate of the test boreholes demonstrated the existence of methane enrichment circles after hydraulic fracturing. It indicated that hydraulic fracturing did act on #5 coal seam in south flank. However, due to the high stress sensitivity of coal seams and the high geo-stress of south flank, the induced artificial fractures in #5 coal seam might close with the decline of the fluid pressure that led to a sharp decline of the methane extraction rate.

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