In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pres...In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pressure changes at protected coal seam during mining upper protective layer. The results show that the taller the mining height at the upper protective layer face, the greater the protection on protected coal seam due to the higher level of pressure release; the upper protective layer face with hard rock floor impedes the pressure release at the protected coal seam, which affects the overall effect of the pressure release at protected coal seam using the protective layer mining method.展开更多
With the increase in mining depth, the danger of coal and gas outbursts increases.In order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration bo...With the increase in mining depth, the danger of coal and gas outbursts increases.In order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration boreholes for draining of pressure relief gas.Based on the principle of overlying strata movement, deformation and pressure relief, a good effect of gas drainage was obtained.The practice in the Panyi coal mine has shown that, after mining the C11coal seam as the protective layer, the relative expansion deformation value of the protected layer C13 reached 2.63%, The permeability coefficient increased 2880 times, the gas drainage rate of the C13 coal seam increased to more than 60%, the amount of gas was reduced from 13.0 to 5.2 m3/t and the gas pressure declined from 4.4 to 0.4 MPa, which caused the danger the outbursts in the coal seams to be eliminated.The result was that we achieved a safe and highly efficient mining operation of the C13 coal seam.展开更多
Based on the occurrence features of Group B coal-seams at a coal mine in the Huainan coal mining area, the elasto-plastic mechanical damage constitutive functions and numerical model for the protective layer excavatio...Based on the occurrence features of Group B coal-seams at a coal mine in the Huainan coal mining area, the elasto-plastic mechanical damage constitutive functions and numerical model for the protective layer excavation were established. With the UDEC2D computer program, after the upper protective layer was mined, the stress field change trends, crack development, and expansion deformation trends of underlying coal rock seams in the floor of the working face were simulated and analyzed. The simulation results show the stress changes in coal rock seams, the evolution process of pre-cracks during the process of upper protective layer mining, the caved zone and fractured zone of the underlying coal rock seams. At the same time, the results from the actual investigation and analysis of protected layer deformation match the simulation values, which verifies the validity and accuracy of numerical simulation results. The study results have an important guiding significance for gas management in low permeability and high gas coal seams with similar mining conditions.展开更多
The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to devel...The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to develop a universal stimulating technology which can increase the permeability in various coal reservoirs.Theoretical analysis and field tests were used to systematically analyze the mechanical mechanisms causing the formation of various levels and types of fractures,such as radial tensile fractures,peripheral tensile fractures,and shear fractures in hydraulic fracturing,and reveal the mechanism of permeability enhancement by fracture network stimulating in surrounding beds and coal reservoirs.The results show that multi-staged perforation fracturing of horizontal wells,hydraulic-jet staged fracturing,four-variation hydraulic fracturing and some auxiliary measures are effective technical approaches to fracture network stimulation,especially the four-variation hydraulic fracturing can stimulate the fracture network in vertical and cluster wells.It is concluded that the fracture network stimulating technology for surrounding beds has significant advantages,such as safe drilling operation,strong stimulation effect,strong adaptability to stress-sensitive and velocity-sensitive beds,and is suitable for coal reservoirs of any structure.Except for the limitation in extremely water-sensitive and high water-yield surrounding beds,the technology can be universally used in all other beds.The successful industrial tests in surface coal bed methane and underground coal mines gas extraction prove that the theory and technical system of fracture network stimulating in surrounding beds and coal reservoirs,as a universally applicable measure,will play a role in the CBM development in China.展开更多
文摘In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pressure changes at protected coal seam during mining upper protective layer. The results show that the taller the mining height at the upper protective layer face, the greater the protection on protected coal seam due to the higher level of pressure release; the upper protective layer face with hard rock floor impedes the pressure release at the protected coal seam, which affects the overall effect of the pressure release at protected coal seam using the protective layer mining method.
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundationof China
文摘With the increase in mining depth, the danger of coal and gas outbursts increases.In order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration boreholes for draining of pressure relief gas.Based on the principle of overlying strata movement, deformation and pressure relief, a good effect of gas drainage was obtained.The practice in the Panyi coal mine has shown that, after mining the C11coal seam as the protective layer, the relative expansion deformation value of the protected layer C13 reached 2.63%, The permeability coefficient increased 2880 times, the gas drainage rate of the C13 coal seam increased to more than 60%, the amount of gas was reduced from 13.0 to 5.2 m3/t and the gas pressure declined from 4.4 to 0.4 MPa, which caused the danger the outbursts in the coal seams to be eliminated.The result was that we achieved a safe and highly efficient mining operation of the C13 coal seam.
基金Supported by the National Natural Science Foundation of China （51004003） the Natural Science Foundation of Ministry of Education of Anhui Province （K J2010A091 ）
文摘Based on the occurrence features of Group B coal-seams at a coal mine in the Huainan coal mining area, the elasto-plastic mechanical damage constitutive functions and numerical model for the protective layer excavation were established. With the UDEC2D computer program, after the upper protective layer was mined, the stress field change trends, crack development, and expansion deformation trends of underlying coal rock seams in the floor of the working face were simulated and analyzed. The simulation results show the stress changes in coal rock seams, the evolution process of pre-cracks during the process of upper protective layer mining, the caved zone and fractured zone of the underlying coal rock seams. At the same time, the results from the actual investigation and analysis of protected layer deformation match the simulation values, which verifies the validity and accuracy of numerical simulation results. The study results have an important guiding significance for gas management in low permeability and high gas coal seams with similar mining conditions.
基金“Research on the formation mechanism of coal seam methane”(No.41002047 and No.40972109)supported by State Natural Sciences Foundation.
文摘The existing reservoir stimulating technologies are only applicable to hard coal but helpless for soft coal,which is one of the main factors hindering the CBM industrialization in China.Therefore,it is urgent to develop a universal stimulating technology which can increase the permeability in various coal reservoirs.Theoretical analysis and field tests were used to systematically analyze the mechanical mechanisms causing the formation of various levels and types of fractures,such as radial tensile fractures,peripheral tensile fractures,and shear fractures in hydraulic fracturing,and reveal the mechanism of permeability enhancement by fracture network stimulating in surrounding beds and coal reservoirs.The results show that multi-staged perforation fracturing of horizontal wells,hydraulic-jet staged fracturing,four-variation hydraulic fracturing and some auxiliary measures are effective technical approaches to fracture network stimulation,especially the four-variation hydraulic fracturing can stimulate the fracture network in vertical and cluster wells.It is concluded that the fracture network stimulating technology for surrounding beds has significant advantages,such as safe drilling operation,strong stimulation effect,strong adaptability to stress-sensitive and velocity-sensitive beds,and is suitable for coal reservoirs of any structure.Except for the limitation in extremely water-sensitive and high water-yield surrounding beds,the technology can be universally used in all other beds.The successful industrial tests in surface coal bed methane and underground coal mines gas extraction prove that the theory and technical system of fracture network stimulating in surrounding beds and coal reservoirs,as a universally applicable measure,will play a role in the CBM development in China.
