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

Zhang, H.; Cheng, Yuanping; Deng, Cunbao; Shu, Longyong; Pan, Zhejun; Yuan, Liang; Cheng, Yuanping; Liu, Qingquan

doi:10.1007/s00603-021-02691-w

Cited by 47 publications

(30 citation statements)

References 37 publications

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“…The large-size holes are favorable for coal body expansion, deformation, migration, and breakage and realize efficient stress unloading and permeability enhancement of soft coal seam. 22 − 28 …”

Section: Methods and Theorymentioning

confidence: 99%

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Zhang

2022

ACS Omega

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Soft and low permeability tectonic coal seams (SLPTCSs) are widely distributed in China. In SLPTCSs, because of the difficulty of gas extraction, coal and gas outburst accidents occur frequently. In this paper, with the principle of stress unloading and permeability enhancement in SLPTCSs analyzed, it is put forward that the key technology to realize stress unloading and permeability enhancement in SLPTCSs is caverning by hydraulic flushing. In addition, the development of hydraulic flushing caverning technology and equipment in China is also further systematically studied. Field tests on the application of highly integrated equipment for caverning by hydraulic flushing have been carried out in the Shijiazhuang coal mine and Pingdingshan no. 8 coal mine. The results show that the widely used drilling and hydraulic flushing packaged equipment and drilling and mechanical cutting packaged equipment for caverning in coal seams can efficiently enlarge caverns in SLPTCSs, reduce the amount of workload for hole-drilling in the coal seam, improve the permeability of the coal seam by 23.9 times, and increase the concentration and pure volume of gas extracted in boreholes by more than two times. Highly integrated hydraulic flushing caverning equipment can realize high-efficiency stress unloading and permeability enhancement of the coal seam, which provides beneficial guidance for gas control of SLPTCSs.

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Section: Methods and Theorymentioning

confidence: 99%

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Zhang

2022

ACS Omega

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“…where ρ b is the methane density at the normal boiling point, 0.424 g/cm 3 ; and T b is the boiling point of methane, 111.5 K.…”

Section: Polanyi Adsorption Potential Theorymentioning

confidence: 99%

“…where n ad is the absolute adsorbed amount of methane at the equilibrium pressure, mol; ρ ad is the density of the adsorbed phase, g/cm 3 .…”

Section: Polanyi Adsorption Potential Theorymentioning

confidence: 99%

“…The estimated world CBM resources buried above 2000 m are around 240 Tm 3 , showing that the global CBM resource is abundant and has a huge potential for production 2 . China has 36.8 Tm 3 , ranking the third‐largest in the world after Russia and Canada 3 . CBM reservoirs are different from the conventional natural gas reservoirs due to coalbed as hydrocarbon source rocks, which results in that there are mainly two types of gas states in coal formation: free gas and adsorbed gas 4–6 .…”

Section: Introductionmentioning

confidence: 99%

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Prediction of methane adsorption capacity in different rank coal at low temperature by the Polanyi‐based isotherm model

Zhao

Wang

et al. 2022

Energy Science & Engineering

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To investigate the adsorption properties of methane in coal under low temperatures, the isothermal adsorption tests of the three coal samples with different metamorphic degrees were conducted at the ambient temperatures of 253.15−293.15 K, and the low‐temperature nitrogen adsorption (LNA) tests of coal were also performed. Then a relational expression of equilibrium pressure, temperature, and methane adsorption capacity (T−P model) was deduced to predict the adsorption isotherm at any other temperature based on the Polanyi adsorption theory. The results show that the gas adsorption capacity of coal can be significantly increased at low temperatures (below 273.15 K), and the adsorbed methane in anthracite is obviously more than that in lean coal and coking coal by the virtue of possessing a larger micropore/transition pore volume and specific surface area. The relations between adsorption potential (ε) and adsorption volume (ω) at different temperatures can be drawn on one single logarithmic curve, and a suitable pseudo‐saturation pressure can be obtained by the improved Amankwah's method. The predicted adsorbed capacities via the T−P model are in line with the measured results at other equilibrium conditions, indicating that the model can contribute to the deep coalbed methane resources estimation and the gas disaster prevention and control in coal mines.

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“…In essence, the driving activity within coal seams induces change within the original stress equilibrium state of coal and rock mass, resulting in its deformation and damage under the comprehensive action of mining stress and gas effect, which leads to the hazard of dynamic disaster occurrence [ 23 ]. In theory, the hazard of dynamic disaster should be closely related to the mining stress state [ 24 ]. Simultaneously, according to mining activity experience, there are some precursor characteristics which occur before dynamic disasters, such as the coal cannon phenomenon and rapid increase in gas concentration (for example, such as a coal and gas outburst) [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

Response Characteristics of Electric Potential and Its Relationship with Dynamic Disaster during Mining Activities: A Case Study in Xuehu Coal Mine, China

Niu

Wang

et al. 2022

IJERPH

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Across the world, coal resource is widely utilized in industrial production. During coal mining activities, dynamic disasters may be induced, such as coal and gas outbursts, or rock burst, resulting in serious accidents or disasters. Previous studies have shown that electric potential (EP) signals can be produced during the deformation and fracture process of coal and rock mass under load. The abnormal response characteristics of EP can reveal the damage evolution and failure feather of coal mass. In this paper, the response characteristics of EP signals are analyzed with high gas testing during mining activities within deep coal seams, and the relationship between the EP response and outburst disaster hazard is studied. The results show that: (1) Under the comprehensive action of mining stress and gas effect, the coal mass was damaged and fractured, which can produce abundant EP signals, while the temporal EP response characteristics can reflect the loading state and damage evolution process inside the coal seam. (2) When coal cannon and a sudden increase of gas concentration occurred in the coal mass, the EP signal was at a high level and fluctuated violently. This can be regarded as precursory information for an outburst risk, which was verified by monitoring the results of mining stress and electromagnetic radiation (EMR). (3) Based on the unilateral inversion imaging method, EP spatial distribution law was studied and abnormal zones with high-value were identified. The zone is close to, or coincident with, the high value interval of EMR intensity and count indexes, which revealed the distribution characteristics of coal damage localization. Hence, EP monitoring results can forecast precursor information of outburst hazards temporally, and identify local zones with outburst hazard spatially. This study provides a new idea and application basis for using the EP method to monitor and prevent coal and rock dynamic disaster hazards in the field.

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

Cited by 47 publications

References 37 publications

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Prediction of methane adsorption capacity in different rank coal at low temperature by the Polanyi‐based isotherm model

Response Characteristics of Electric Potential and Its Relationship with Dynamic Disaster during Mining Activities: A Case Study in Xuehu Coal Mine, China

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