Investigation of the influence of gas fracturing on fracturing characteristics of coal mass and gas extraction efficiency based on a multi-physical field model

Author(s):  
Yi Xue ◽  
Jia Liu ◽  
P.G. Ranjith ◽  
Xin Liang ◽  
Songhe Wang
2013 ◽  
Vol 634-638 ◽  
pp. 3282-3288
Author(s):  
Chang Hong Xie

In order to solve technical problems which restricted coal mining operation, such as low penetrability of coal mass and low efficiency of gas extraction, according to geological mining condition of Yuyang Mine, Crossing Borehole Hydraulic Fracturing system was designed and investigated in N3704 west gas tunnel (below). The system was based on coal or rock mass hydraulic fracturing theory and gas flow theory. Through the experimental study of fracture and analysis of fracturing effect after inspection, the result of field test shows that Crossing Borehole Hydraulic Fracturing system could improve the gas extraction efficiency significantly. The test result provides a basis for hydraulic fracturing operation in other mines.


2019 ◽  
Vol 11 (23) ◽  
pp. 6877
Author(s):  
Yajing Zhang ◽  
Jingfeng Yuan ◽  
Lingzhi Li ◽  
Hu Cheng

Understanding the motivations that stimulate homebuyers’ green purchasing behavior can increase market demand for green products, especially considering the comparably low market share of green products worldwide. In this context, various studies have been conducted examining consumers’ intentions to pay for green products. Nevertheless, there is still limited research on evaluating homebuyers’ purchasing behavior toward green residential buildings. This study argues that the value of green residential buildings (GRBs) affects their adoption, and thus exerts an invisible force on homebuyers’ purchasing behavior. It also finds that field theory provides a scientific perspective on this phenomenon. Thus, this paper proposes a value field model for evaluating homebuyers’ GRB purchasing behavior based on physical field theory and psychology field theory. In particular, physical field theory provides the measurement formula, while psychological field theory explains the effect of the force stimulating homebuyers’ purchasing intention, and ultimately influencing their purchasing behavior. The initial model consisted of a field source (green perceived value), target charge (GRB demand), distance (psychological distance), and value field factor. As the value field factor was calculated to be approximately equal to 1, the final model is a composite of a field source (green perceived value), target charge (GRB demand), and distance (psychological distance). The results validate the construction of the value field model on the basis of field theory. This research contributes to the body of knowledge by analyzing GRB value and provides a clearer understanding of how GRBs and the environment combine to fulfill homebuyers’ requirements and influence their GRB purchasing behavior.


2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiaoyang Cheng ◽  
Qinghua Zhang ◽  
Zhigang Zhang ◽  
Yunlong Zou ◽  
Guo Junjie

Coal seam permeability is one of the key factors influencing the gas extraction efficiency, which is of great significance to reduce coal and gas dynamic disasters in gassy coal mines. Hydraulic slotting technique is an effective method to stimulate the coal reservoir, but the selection of slotting key parameters has great impact on gas extraction efficiency. For this reason, the hydraulic slotting model was established by using FLAC3D software to analyze the stress distribution before and after slotting. Then, the influence of borehole diameter, slotting width, and slotting length on coal seam stress relief is also discussed. The results show that the slotting width has a great influence on the stress relief of the coal seam, while the borehole diameter and slotting length have no obvious influence on that. Based on the results of numerical simulation, field tests were carried out in Sangshuping NO.2 coal mine. The results show that the coal seam stress can be fully released, resulting in the improvement of coal seam permeability. The gas extraction efficiency can be highly enhanced by hydraulic slotting. This research achievement provides the guidance basis for high-stress water jet slotting technology with adaptive selection of slotting parameters in different geological conditions.


Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Hai Pu ◽  
Liqiang Zhang ◽  
Xu Dong ◽  
Tao Jing ◽  
Xu Junce

Coalbed methane is always a major hidden danger that affects mining safety in coal mines. In the study of coal seam water injection to control gas disaster, the increase of free water content is helpful to destroy the integrity of coal seam and to promote the flow of gas in fractures. However, when the free water fills the fracture space, it will increase the flow resistance of gas, and then will reduce the gas extraction efficiency. At present, there is currently no mathematical model describing the effects of coal seam water injection that combines these two aspects on gas drainage. In this study, a series of experiments were conducted to study the differences in mechanical property changes under wetting conditions with different coal samples. The experimental results show that the elastic modulus and compressive strength decrease as an exponential function with increasing water pressure. Based on the experimental results, a gas-liquid-solid coupling model including effective stress change and gas desorption is established and used to predict a field gas extraction application. According to the results of the numerical model, In the plastic failure zone of coal seam, the permeability increases, the elastic modulus drops and gas migrates faster. In the water wetting zone, the free water occupies the fracture space, which blocks the gas migration channel. The overall effect of water injection on gas extraction depends on which impact plays a dominant role. The established gas drainage model is validated by field data and can reflect the pattern of borehole damage and gas drainage under water injection.


Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Pengfei Cui ◽  
Banghua Yao ◽  
Yong Liu ◽  
Jianping Wei ◽  
Zhihui Wen ◽  
...  

Determining the width of the stress relief zone on roadway surrounding rocks is the premise to optimize drilling borehole effect and increase gas extraction efficiency. In this study, a new width measurement method of the stress relief zone on the roadway surrounding rocks was proposed, which determined the width according to gas pressure attenuation speeds in roadway boreholes at different depths. Then, the variation curve of the gas pressure in boreholes at different depths with the time was gained through a field test. On this basis, laws of the gas pressure attenuation and the gas transmission and loss in boreholes at different depths were explored through a numerical simulation based on COMSOL Multiphysics, thus concluding the stress on roadway surrounding rocks, the distribution of plastic zones, and the stress-permeability relation. The scientificity of the proposed method was illustrated theoretically. Finally, the proposed method was verified by the field test data and numerical simulation results of the gas extraction at different sealing depths. Research results demonstrate that the pressure in boreholes attenuates in the logarithmic function pattern. The attenuation speed decreases with the increase of the drilling depth. The width of the stress relief zone on roadway surrounding rocks in the studied area was determined to be about 11 m according to the proposed method. Both the numerical simulation and the field test of the gas extraction efficiency prove the feasibility and validity of the proposed method in determining the sealing depth of the borehole for the gas extraction. Research conclusions are of important significance to enrich width measurement methods of the stress relief zone on roadway surrounding rocks and to optimize sealing parameters of underground boreholes for gas extraction.


2018 ◽  
Vol 64 (2) ◽  
pp. 55-65
Author(s):  
M. Kwietniewski ◽  
D. Miedzińska ◽  
T. Niezgoda

AbstractThe problem of effective gas extraction from Polish shale rocks is an interesting research subject for scientists. A properly selected proppant, which protects cracks from closing during the fracturing process, inestimably contributes to an increase of extraction. Grains of proppant are transported along with a fracturing medium to reach the deepest regions of the crack. The proper support of the crack provides an easy flow of gas, therefore it is important in terms of extraction efficiency. This paper shows the interactions of a proppant grain with the crack surface in shale rock. FEM analysis was conducted to observe the stress region, which is generated as a result of pressing the grain into the crack surface. A model of a sphere which was pressed into the rock model with constant velocity was applied. The received results of stress depend on material properties and a range of proppant grain pressing.


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