Improving the permeability of coal seam is the key factor to realize efficient and safe mining of coalbed gas.In order to study the effect of high-voltage pulse breakdown on coal permeability,the multi-field coupling ...Improving the permeability of coal seam is the key factor to realize efficient and safe mining of coalbed gas.In order to study the effect of high-voltage pulse breakdown on coal permeability,the multi-field coupling high-voltage pulse crack coal permeability test equipment was used to carry out breakdown tests on bituminous coal samples soaked in conductive fluid under different voltage conditions.Subsequently,the breakdown effect of high voltage electrical pulse was characterized by comparison of breakdown energy,coal sample permeability and pore distribution,and the mechanism of voltage effect and the concentration of conductive liquid on the cracking effect was explored.The results show that the higher the pulse voltage,the faster the formation rate of plasma channel in coal and the more obvious the breakdown effect.With the increase of pulse voltage,the increment of coal porosity first increases and then decreases,the maximum increase is 31.4%,and the cracking effect is obvious.By comparing the changes of permeability and pore distribution of coal samples before and after pulse voltage treatment,it is found that conductive liquid can improve the conductivity in fragile cracks,crack growth and pore connectivity under pulse voltage.This paper provides a basis for high voltage electric pulse as a method to enhance coal permeability.展开更多
In this study,to investigate the mechanism through which high-voltage electrical pulses(HVEPs)enhance coal permeability and improve coalbed methane(CBM)extraction efficiency,liquid nitrogen adsorption analysis,nuclear...In this study,to investigate the mechanism through which high-voltage electrical pulses(HVEPs)enhance coal permeability and improve coalbed methane(CBM)extraction efficiency,liquid nitrogen adsorption analysis,nuclear magnetic resonance,infrared spectroscopy,and scanning electron microscopy were performed on HVEPtreated coal samples.The mentioned techniques were used to analyze the crack structures,pore distribution patterns,and changes in the chemical functional groups in the coal samples.The permeability enhancement mechanism of HVEP in coal was explored from macroscopic,mesoscopic,and microscopic perspectives.The chemical modification of coal through the breakdown of its oxygen-containing functional groups reduced the gas adsorption capacity of the coal samples and enhanced their desorption abilities.Simultaneously,the number of pores within the bottleneck pore interval of the coal samples increased significantly.The closed pores transformed into semi-closed and open pores.The pore volume was 2.86 times the pore volume of the original coal,while the pore specific surface area growth rate was 48.67%.This pronounced pore expansion effect eliminated the bottleneck pore interval,which reduced CBM seepage efficiency and enabled cross-scale CBM transport.Extensive parallel fractures and fissures appeared throughout the coal body.The connectivity within the porefracture network was enhanced substantially.This improved connectivity provided efficient pathways for gas transport.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant no.52274173).
文摘Improving the permeability of coal seam is the key factor to realize efficient and safe mining of coalbed gas.In order to study the effect of high-voltage pulse breakdown on coal permeability,the multi-field coupling high-voltage pulse crack coal permeability test equipment was used to carry out breakdown tests on bituminous coal samples soaked in conductive fluid under different voltage conditions.Subsequently,the breakdown effect of high voltage electrical pulse was characterized by comparison of breakdown energy,coal sample permeability and pore distribution,and the mechanism of voltage effect and the concentration of conductive liquid on the cracking effect was explored.The results show that the higher the pulse voltage,the faster the formation rate of plasma channel in coal and the more obvious the breakdown effect.With the increase of pulse voltage,the increment of coal porosity first increases and then decreases,the maximum increase is 31.4%,and the cracking effect is obvious.By comparing the changes of permeability and pore distribution of coal samples before and after pulse voltage treatment,it is found that conductive liquid can improve the conductivity in fragile cracks,crack growth and pore connectivity under pulse voltage.This paper provides a basis for high voltage electric pulse as a method to enhance coal permeability.
基金supported by the National Key Research and Development Program of China(No.2024YFC3013804)the National Natural Science Foundation of China(No.52274173)the Open Fund of State Key Laboratory of Coal Mine Disaster Dynamics and Control(No.2011DA105287-FW202305)。
文摘In this study,to investigate the mechanism through which high-voltage electrical pulses(HVEPs)enhance coal permeability and improve coalbed methane(CBM)extraction efficiency,liquid nitrogen adsorption analysis,nuclear magnetic resonance,infrared spectroscopy,and scanning electron microscopy were performed on HVEPtreated coal samples.The mentioned techniques were used to analyze the crack structures,pore distribution patterns,and changes in the chemical functional groups in the coal samples.The permeability enhancement mechanism of HVEP in coal was explored from macroscopic,mesoscopic,and microscopic perspectives.The chemical modification of coal through the breakdown of its oxygen-containing functional groups reduced the gas adsorption capacity of the coal samples and enhanced their desorption abilities.Simultaneously,the number of pores within the bottleneck pore interval of the coal samples increased significantly.The closed pores transformed into semi-closed and open pores.The pore volume was 2.86 times the pore volume of the original coal,while the pore specific surface area growth rate was 48.67%.This pronounced pore expansion effect eliminated the bottleneck pore interval,which reduced CBM seepage efficiency and enabled cross-scale CBM transport.Extensive parallel fractures and fissures appeared throughout the coal body.The connectivity within the porefracture network was enhanced substantially.This improved connectivity provided efficient pathways for gas transport.
