A pressure relief gas extraction technical model of a typical mining area is proposed based on coal and gas simultaneous extraction theory. Flac3 Dwas employed to model vertical stress and displacement contour plot ch...A pressure relief gas extraction technical model of a typical mining area is proposed based on coal and gas simultaneous extraction theory. Flac3 Dwas employed to model vertical stress and displacement contour plot characteristics of non-outburst coal seam(No. 4) on top of outburst coal seam(No. 2) along strike and incline directions. Field investigations were also conducted to verify the scientific nature of the simulation. The results demonstrate that gas pressure in No. 2 coal seam dropped to approximately 0.55 MPa in the pressure relief multi-coal seam. The highest expansion rate of the coal mine reached up to 2.58%.The pressure-relief angle was 76° along the incline direction and 60° along the strike direction. As the expansion rate and pressure-relief angle increased and the gas pressure decreased, a large amount of gas flowed into the gob of No. 4 from No. 2 coal seam and was later discharged through specific gas pipes,which eliminated No. 2 outburst risks. This study resulted in positive outcomes in that gas extraction time was reduced by 13.5 days, due to pressure relief, and drilling work load was reduced by 0.1161 m/t coal. This method ensures that gas is discharged from the outburst coal seam quickly and safely,demonstrating that the proposed technical model of pressure-relief gas extraction is effective in a multi-coal seam region.展开更多
Against the particularity of stratum-structure in ＂three soft＂ mine areas, according to rock indoor test and on-site sucking experiment, discussed the characteristics of argillization, compression fracture and sucki...Against the particularity of stratum-structure in ＂three soft＂ mine areas, according to rock indoor test and on-site sucking experiment, discussed the characteristics of argillization, compression fracture and sucking technique of soft coal with low permeability. It is clearly pointed out that the gas can be highly effectively sucked only by compression fracture along the occurrence of the coal seam, creating inter-seams crack belt because of the difference of bulgy deformation. After the flooding experiment in the 24080 workface of Pingdingshan No. 10 mine, the average single-bore volume of gas increases from 77 m3 to 7 893 mS, while decay cycle extended from 7 days to 80-90 days. Also, the single-bore extracting rate of gas increases to 33%.展开更多
Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme- ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger move...Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme- ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing; the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 LJmin at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.展开更多
In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal ...In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal mining industry. How- ever, during the engineering applications, it is observed that the efficiency of gas drainage initially improves, but reduces there- after. Thus, it is speculated that the contrasts in coalbed methane drainage efficiency may reflect variation of the closure be- havior of the artificial fracture created. Based on comprehensive gas drainage monitoring data in underground coal mines, the work presented herein uses numerical simulation to show the behavior of the time-dependent closure of coal seam fractures as- sociated with various levels of waterjet fracturing parameters and geomechanical conditions.展开更多
This paper presented a method to create artificial fractures along the existing gas drainage borehole and increase the permeability of the coalbed using a high pressure waterjet cutting system.The field work conducted...This paper presented a method to create artificial fractures along the existing gas drainage borehole and increase the permeability of the coalbed using a high pressure waterjet cutting system.The field work conducted in Rujigou Colliery, Shenhua Ningxia Coal Group demonstrate that the coalbed permeability is increased, and accordingly, gas drainage efficiency is improved up to 3 to 6 times over the traditional methods using high pressure waterjet technique.Also, based on the monitoring data, the conceptual model for gas drainage process associated with different mining activities has been proposed, and few major advantages using waterjet assistance method have been identified.展开更多
基金support from the National Key Basic Research and Development Program (No. 2011CB201206)the Junior Fellowships for Advanced Innovation Think-Tank Program from China Association for Science and Technology (No. DXB-ZKQN-2016-048)
文摘A pressure relief gas extraction technical model of a typical mining area is proposed based on coal and gas simultaneous extraction theory. Flac3 Dwas employed to model vertical stress and displacement contour plot characteristics of non-outburst coal seam(No. 4) on top of outburst coal seam(No. 2) along strike and incline directions. Field investigations were also conducted to verify the scientific nature of the simulation. The results demonstrate that gas pressure in No. 2 coal seam dropped to approximately 0.55 MPa in the pressure relief multi-coal seam. The highest expansion rate of the coal mine reached up to 2.58%.The pressure-relief angle was 76° along the incline direction and 60° along the strike direction. As the expansion rate and pressure-relief angle increased and the gas pressure decreased, a large amount of gas flowed into the gob of No. 4 from No. 2 coal seam and was later discharged through specific gas pipes,which eliminated No. 2 outburst risks. This study resulted in positive outcomes in that gas extraction time was reduced by 13.5 days, due to pressure relief, and drilling work load was reduced by 0.1161 m/t coal. This method ensures that gas is discharged from the outburst coal seam quickly and safely,demonstrating that the proposed technical model of pressure-relief gas extraction is effective in a multi-coal seam region.
文摘Against the particularity of stratum-structure in ＂three soft＂ mine areas, according to rock indoor test and on-site sucking experiment, discussed the characteristics of argillization, compression fracture and sucking technique of soft coal with low permeability. It is clearly pointed out that the gas can be highly effectively sucked only by compression fracture along the occurrence of the coal seam, creating inter-seams crack belt because of the difference of bulgy deformation. After the flooding experiment in the 24080 workface of Pingdingshan No. 10 mine, the average single-bore volume of gas increases from 77 m3 to 7 893 mS, while decay cycle extended from 7 days to 80-90 days. Also, the single-bore extracting rate of gas increases to 33%.
基金the National Natural Science Foundation of China(No.51274195)the National Basic Research Program of China(No.2011CB201205)+1 种基金the Ph.D.Foundation of Henan Polytechnic University(No.60207005)the Education Department of Hennan Province(No.14B440007)
文摘Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme- ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing; the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 LJmin at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.
文摘In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal mining industry. How- ever, during the engineering applications, it is observed that the efficiency of gas drainage initially improves, but reduces there- after. Thus, it is speculated that the contrasts in coalbed methane drainage efficiency may reflect variation of the closure be- havior of the artificial fracture created. Based on comprehensive gas drainage monitoring data in underground coal mines, the work presented herein uses numerical simulation to show the behavior of the time-dependent closure of coal seam fractures as- sociated with various levels of waterjet fracturing parameters and geomechanical conditions.
文摘This paper presented a method to create artificial fractures along the existing gas drainage borehole and increase the permeability of the coalbed using a high pressure waterjet cutting system.The field work conducted in Rujigou Colliery, Shenhua Ningxia Coal Group demonstrate that the coalbed permeability is increased, and accordingly, gas drainage efficiency is improved up to 3 to 6 times over the traditional methods using high pressure waterjet technique.Also, based on the monitoring data, the conceptual model for gas drainage process associated with different mining activities has been proposed, and few major advantages using waterjet assistance method have been identified.
