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, Rong

doi:10.1021/acsomega.2c01465

Cited by 11 publications

(8 citation statements)

References 34 publications

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“…Determining the coal-breaking pressure of hydraulic punching is of great significance for improving the coal- breaking efficiency of hydraulic punching. [15][16][17] According to the relevant data collected and measured on-site, the threshold value of coal-breaking water pressure, theoretical threshold speed of coal-breaking water pressure, the threshold value of coal-breaking incident pressure and other relevant parameters in the process of hydraulic punching test are determined. The crushing strength of coal under the impact of high-pressure water jet can be calculated according to the following formula:…”

Section: Numerical Simulation Of Reasonable Parameters Of Hydraulic P...mentioning

confidence: 99%

Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

Min,

Chen,

Wang

et al. 2023

Energy Science & Engineering

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Aiming at the application of hydraulic punching technology in soft, low permeability, and high gas coal seams in Changping Coal Mine, there are problems such as large workload, poor permeability enhancement effect, and the formation of “blank zones” in the pressure relief and permeability enhancement areas caused by workers' blind construction. By using a combination of theoretical analysis, numerical simulation, and on‐site practice, the threshold pressure for punching and breaking coal was calculated. The simulation analysis determined the reasonable key parameters for hydraulic punching through layered drilling, providing theoretical support for engineering applications; and the application effect of key parameters was investigated in the 5302 bottom extraction roadway of Changping Coal Mine. The research results show that the threshold value of incident pressure for punching and breaking coal in the No. 3 coal seam of Changping Coal Mine is 4.26 MPa, the reasonable hydraulic punching water pressure is 15 MPa, the punching angle is 60°, the diameter of the punching hole is not more than 0.8 m, and the punching time is 120 min; when the punching water pressure is lower than 4.0 MPa, effective coal flushing cannot be achieved. When the water pressure is between 4.0 and 15.0 MPa, the total amount of coal flushing is positively correlated with the punching water pressure; under the determined reasonable parameter punching conditions, the extraction influence radius is 8.9 m, the effective extraction radius is 5 m, and the average pure gas extraction volume is 0.089 m3/min. Under this parameter, hydraulic punching technology effectively improves the permeability characteristics of coal seams, which is conducive to long‐term gas extraction and has a significant effect on pressure relief and drainage promotion.

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Section: Numerical Simulation Of Reasonable Parameters Of Hydraulic P...mentioning

confidence: 99%

Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

Min,

Chen,

Wang

et al. 2023

Energy Science & Engineering

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“…At present, gas control technologies and processes are mainly consisted of hydraulic technology, gas-phase fracturing, deep-hole pre-splitting blasting, etc. − The hydraulic process mainly forms macroscopic cracks through high-pressure hydraulic fracturing, which creates a flow channel for gas migration to improve the permeability of coal seams. − However, the cracks formed by the hydraulic measures have a short maintenance time, the fracture channels are quickly closed, and under the action of water, coal slime is generated to block the cracks, which accelerates the decline of permeability of soft coal seams, and the local permeability enhancement effect is slowed down or even stopped. The deep-hole pre-splitting blasting (explosive) produces dynamic pressure shock, stress wave superposition, and explosive gas drives the crack growth of coal seam, which results in the local fracture field and improves the gas drainage efficiency of coal seam. , Gas-phase fracturing mainly uses the impact load generated by the instantaneous release of liquid CO 2 to act on the coal body to form a crushing zone, realizes the pressure relief and permeability enhancement of the coal seam, improves the gas drainage efficiency, and achieves the purpose of permeability enhancement. , Gas-phase fracturing and deep-hole pre-splitting blasting only use local coal.…”

Section: Introductionmentioning

confidence: 99%

Stress Relief and Permeability Enhancement with Hydraulic Fracturing in Overlying Key Strata of Deep and Soft Coal Seams

Liu

Wang

et al. 2023

ACS Omega

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The technical problems of high in situ stress, high gas pressure, high gas content, and low coal seam permeability are widespread in deep soft coal seam excavation, which leads to frequent occurrences of dynamic phenomena, such as coal cannons and blowout holes. Based on the high-pressure hydraulic fracturing technology and process, this study puts forward a new technology of gas drainage in deep and soft coal seams by fracturing the overlying key strata to cut off the stress transmission path among coal and rock strata. According to the theories of key layer and masonry beams, the distribution locations of the main and subkey strata are determined, and based on uniaxial compression and Brazilian splitting experiments, the mechanical parameters of key stratum were tested. Combined with the results of numerical simulation and field test, initial pressure and fracturing radius of hydraulic fracturing technology for overlying key strata were determined, the stress relief effect and permeability variation law of coal seam after hydraulic fracturing in the main and subkey strata were analyzed, and then technical schemes for simultaneous fracturing of the key layer were designed. Field application results showed that the stress concentration phenomenon in soft coal seam excavation had been alleviated, and the stress relief effect of coal seam and the permeability were increased obviously. The volume and concentration of gas drainage were increased by 10 and 11%, respectively, the gas amount by 1.22 times; the frequency of dynamic phenomena such as coal cannons decreased by 95%, the gas concentration in return air flow by 20% during mining processes. This paper provided an innovative technical idea and process for gas control in deep and soft coal seam excavation, which could effectively solve the common and difficult problems about frequent occurrences of excessive gas concentration and dynamic phenomena.

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“…Zhang et al established a Multiphysics field coupling model and analyzed the mechanism of hydraulic flushing to strengthen gas extraction using the numerical simulation method of FLAC3D and COMSOL . Zhang et al conducted a systematic study on developing hydraulic flushing technology and equipment in China . Li et al discussed the impact of hydraulic flushing on gas drainage efficiency in soft coal seams …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…25 Zhang et al conducted a systematic study on developing hydraulic flushing technology and equipment in China. 26 Li et al discussed the impact of hydraulic flushing on gas drainage efficiency in soft coal seams. 27 Most of the above studies have been conducted using the Mohr−Coulomb model, without considering the strain-softening of borehole surrounding rocks.…”

Section: Introductionmentioning

confidence: 99%

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Study on the Effect of Strain-Softening on Permeability and Gas Pressure in Surrounding Rocks of a Hydraulic Flushing Borehole

et al. 2023

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Hydraulic flushing gas extraction technology is gradually being applied in coal mines because it can effectively improve the gas extraction efficiency. This study aimed to explore the effect of strain-softening on permeability and gas pressure, due to the deficiency of previous studies on hydraulic flushing that did not consider the strain-softening of surrounding rocks. First, we analyzed the essence of strain-softening based on previous studies and proved the existence of strain-softening in surrounding rocks of the hydraulic flushing borehole by a field example. Subsequently, we established gas extraction models for different borehole diameters with and without considering strain-softening through the permeability evolution equation, the gas migration equation, and the strain-softening equation. We found that strain-softening significantly effects the permeability and gas pressure of the surrounding rocks of the borehole: the larger the diameter, the greater the effect on strain-softening. Compared with strain-softening not considered, the permeability, the permeability increase range, and the gas extraction standard range in surrounding rocks of hydraulic flushing boreholes will increase under the same borehole diameter when strain-softening is considered. The borehole diameter increases from 0.113 to 0.7 m, and the increases in permeability are 592.76 × 10 −12 , 614.25 × 10 −12 , 615.13 × 10 −12 , and 655.29 × 10 −12 m 2 , respectively, the increases in permeability increase radius are 0.050, 0.121, 0.193, and 0.255 m, respectively, and the increase in gas extraction standard range radius under the two indicators are 0.119, 0.124, 0.190, 0.253 m and 0.052, 0.102, 0.150, 0.191 m, respectively. The gas pressure distribution in surrounding rocks of the borehole will also be changed by considering strain-softening, resulting in a slowly increasing gas pressure zone near the borehole: the larger the diameter, the greater the zone. Our research results proved that it is necessary to consider the strain-softening of surrounding rocks when studying gas extraction through hydraulic flushing boreholes. Moreover, we provide a novel explanation for the mechanism of gas extraction through hydraulic flushing boreholes based on the study's results. The finding of this study can help better understand the mechanism of enhanced gas extraction through hydraulic flushing boreholes.

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

Cited by 11 publications

References 34 publications

Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

Stress Relief and Permeability Enhancement with Hydraulic Fracturing in Overlying Key Strata of Deep and Soft Coal Seams

Study on the Effect of Strain-Softening on Permeability and Gas Pressure in Surrounding Rocks of a Hydraulic Flushing Borehole

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