A Novel In-Seam Borehole Discontinuous Hydraulic Flushing Technology in the Driving Face of Soft Coal Seams: Enhanced Gas Extraction Mechanism and Field Application

2021 ◽  
Author(s):  
Hao Zhang ◽  
Yuanping Cheng ◽  
Cunbao Deng ◽  
Longyong Shu ◽  
Zhejun Pan ◽  
...  
Keyword(s):  
Field Application ◽  
Gas Extraction ◽  
Coal Seams ◽  
Extraction Mechanism ◽  
Soft Coal

The New Technology of Hydraulic Fracturing Soft Coal Rock Permeability Improvement

2014 ◽  
Vol 1030-1032 ◽  
pp. 1255-1259 ◽  
Author(s):  
Xue Xi Chen ◽  
Yan Ke Zhang ◽  
Yong Xu ◽  
Rui Qing Bi
Keyword(s):  
Coal Seam ◽  
New Technology ◽  
Water Injection ◽  
Injection Pressure ◽  
Field Application ◽  
Good Effect ◽  
Gas Extraction ◽  
Soft Coal ◽  
Coal Rock ◽  
Soft Coal Seam

According to the low intensity, good plasticity in soft coal seam, the effect of direct fracturing to increase permeability was not ideal, the new technology of hydraulic fracture soft coal rock was proposed, which increased coal seam permeability. Its technical principles and characteristics were researched. Water injection pressure was analyzed, including injection time, parameters of the technology and so on. Field application experiment and effect of inspection were conducted. The results showed that the concentration of gas extraction increased 4.3 times, and the gas extraction flow increased 6.2times. The technology has a good effect of fracturing and advantages in enlarging the released area and decreasing diffusion seepage resistance of coal seam. Most important, the technology has broad application prospects in soft coal seam.

scholarly journals Numerical simulation of boreholes for gas extraction and effective range of gas extraction in soft coal seams

2019 ◽  
Vol 7 (5) ◽  
pp. 1632-1648 ◽  
Author(s):  
Pan Wei ◽  
Changwen Huang ◽  
Xuelong Li ◽  
Shoujian Peng ◽  
Yanan Lu
Keyword(s):  
Numerical Simulation ◽  
Effective Range ◽  
Gas Extraction ◽  
Coal Seams ◽  
Soft Coal

scholarly journals Hydraulic flushing in soft coal sublayer: Gas extraction enhancement mechanism and field application

2019 ◽  
Vol 7 (5) ◽  
pp. 1970-1993
Author(s):  
Hao Zhang ◽  
Yuanping Cheng ◽  
Liang Yuan ◽  
Liang Wang ◽  
Zhejun Pan
Keyword(s):  
Field Application ◽  
Gas Extraction ◽  
Enhancement Mechanism ◽  
Soft Coal

scholarly journals Coupling numerical model of hydraulic fracturing seepage in soft coal based on elastoplastic damage

2020 ◽  
Vol 198 ◽  
pp. 01038
Author(s):  
LI Liangwei
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Hydraulic Fracturing ◽  
Yield Criterion ◽  
Calculation Model ◽  
Field Application ◽  
Soft Coal ◽  
Plastic Shear Strain ◽  
Strain Relationship ◽  
Relationship Equation

In order to guide the field application of hydraulic fracturing of soft coal in coal mine, based on the elastic-plastic damage theory, the coupling numerical model of soft coal hydraulic fracturing seepage was studied. The porosity strain relationship equation, permeability strain relationship equation, the relationship between permeability and volume plastic tensile strain and volume plastic shear strain of coal and rock mass are derived, and the plastic correction equation and softening parameters are defined. The stress coupling equation and yield criterion are programmed and embedded into the finite difference software FLAC3D for numerical solution. The numerical simulation shows that the numerical calculation model of soft coal hydraulic fracturing conforms to the actual law, and the field fracturing radius investigation experiment is consistent with the numerical simulation results.

Massive Hydraulic Fracturing to Control Gas Outbursts in Soft Coal Seams

2022 ◽  
Author(s):  
Shuaifeng Lyu ◽  
Shengwei Wang ◽  
Junyang Li ◽  
Xiaojun Chen ◽  
Lichao Chen ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Coal Seams ◽  
Soft Coal

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 Experimental Development of Coal-Like Material with Solid-Gas Coupling for Quantitative Simulation Tests of Coal and Gas Outburst Occurred in Soft Coal Seams

Processes ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 155 ◽  
Author(s):  
Xingkai Wang ◽  
Wenbing Xie ◽  
Zhili Su ◽  
Qingteng Tang
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Influencing Factors ◽  
Co2 Sequestration ◽  
Range Analysis ◽  
Coal Seams ◽  
Gas Outburst ◽  
Soft Coal ◽  
Coal Powder ◽  
Adsorption Desorption

Solid-gas coupling coal-like materials are essential for simulating coal and gas outbursts and the long-term safety study of CO2 sequestration in coal. However, reported materials still differ substantially from natural coal in mechanical, deformation and gaseous properties; the latter two aspects are common not considered. There is a lack of a definite and quantitative preparation method of coal-like materials with high similarity for future reference. Here, 25 groups of raw material ratios were designed in the orthogonal experiment using uniaxial compression, shearing and adsorption/desorption tests. Experiment results indicated that the coal-like materials were highly similar to soft coals in properties mentioned above. And range analysis revealed the key influencing factors of each mechanical index. The gypsum/petrolatum ratio controls the density, compressive strength, elastic modulus, cohesion and deformation characteristic. The coarse/fine coal powder (1–2 and 0–0.5 mm) controls the internal friction angle and is the secondary controlling factor for compressive strength and elastic modulus. The effect of coal particle size on the sample strength was studied using scanning electron microscope (SEM). When the gypsum/petrolatum ratio increased, the deformation characteristics changed from ductile to brittle. The different failure modes in the samples were revealed. The coal powder content is a key in the gas adsorption/desorption properties and an empirical formula for estimating the adsorption capacity was established. Based on the range analysis of experimental results, a multiple linear regression model of the mechanical parameters and their key influencing factors was obtained. Finally, a composition closely resembling the natural coal was determined, which differs by only 0.47–7.41% in all parameters except porosity (11.76%). Possible improvements and extension to similar materials are discussed. The findings of this study can help for better understanding of coal and gas outburst mechanism and stability of CO2 sequestration in soft coal seams.

scholarly journals A Study of the Laws of Abnormal Gas Emissions and the Stability Controls for Coal Mine Walls in Deeply Buried High-Gas Coal Seams

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Anying Yuan ◽  
Hao Hu ◽  
Qiupeng Yuan
Keyword(s):  
Coal Seam ◽  
Water Content ◽  
Coal Mine ◽  
Gas Diffusion ◽  
Hard Coal ◽  
Coal Seams ◽  
Gas Emissions ◽  
Soft Coal ◽  
Pressure Water ◽  
Gas Coal

At the present time, it is considered to be of major significance to study the gas emission law and stability controls of coal bodies in deeply buried high-gas coal seams. For this reason, in view of the specific problems of gas emissions caused by unstable rib spalling in coal mine walls, comprehensive research methods were adopted in this study, in order to conduct an in-depth examination of micropore structure parameters, gas desorption, diffusion laws, and coal stability levels. The results showed that the development degree of the pores above the micropores, as well as the small pores in soft coal seams, was better than those observed in hard coal seams. In addition, the gas outburst phenomenon was found to have more easily formed in the soft coal seams. The coal body of the No. 6 coal seam in the Xieqiao Coal Mine not only provided the conditions for gas adsorption but also provided dominant channels for gas diffusion and migration. The abnormal gas emissions of the No. 6 coal seam were jointly caused by the relatively developed pores above the small holes in the coal body, rib spalling of coal mine walls, and so on. The research results also revealed the evolution law of mechanical characteristics of the No. 6 coal seam under different water content conditions. It was found that the strength levels of the No. 6 coal seam first increased and then decreased with the increase in water content, and the water content level at the maximum strength of the coal seam was determined to be 7.09%. This study put forward a method which combined the water injection technology of long-term static pressure water injections in deep coal mining holes and real-time dynamic pressure water injections in shallower holes. Field experiments were successfully carried out.

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