In the concurrent extraction of coal and gas,the quantitative assessment of evolving characteristics in mining-induced fracture networks and mining-enhanced permeability within coal seams serves as the cornerstone for...In the concurrent extraction of coal and gas,the quantitative assessment of evolving characteristics in mining-induced fracture networks and mining-enhanced permeability within coal seams serves as the cornerstone for effective gas extraction.However,representing mining-induced fracture networks from a three-dimensional(3D)sight and developing a comprehensive model to evaluate the anisotropic mining-enhanced permeability characteristics still pose significant challenges.In this investigation,a field experiment was undertaken to systematically monitor the evolution of borehole fractures in the coal mass ahead of the mining face at the Pingdingshan Coal Mining Group in China.Using the testing data of borehole fracture,the mining-induced fracture network at varying distances from the mining face was reconstructed through a statistical reconstruction method.Additionally,utilizing fractal theory,a model for the permeability enhancement rate(PER)induced by mining was established.This model was employed to quantitatively depict the anisotropic evolution patterns of PER as the mining face advanced.The research conclusions are as follows:(1)The progression of the mining-induced fracture network can be classified into the stage of rapid growth,the stage of stable growth,and the stage of weak impact;(2)The PER of mining-induced fracture network exhibited a typical progression that can be characterized with slow growth,rapid growth and significant decline;(3)The anisotropic mining-enhanced permeability of the reconstructed mining-induced fracture networks were significant.The peak PER in the vertical direction of the coal seam is 6.86 times and 4446.38 times greater than the direction perpendicular to the vertical thickness and the direction parallel to the advancement of the mining face,respectively.This investigatione provides a viable approach and methodology for quantitatively assessing the anisotropic PER of fracture networks induced during mining,in the concurrent exploitation of coal and gas.展开更多
Supercritical CO_(2) fracturing is an important development trend to reach the goal of"dual carbon"and avoid the problem that hydraulic fracturing is influenced by water resource.In order to clarify the trans...Supercritical CO_(2) fracturing is an important development trend to reach the goal of"dual carbon"and avoid the problem that hydraulic fracturing is influenced by water resource.In order to clarify the transport characteristics of proppant in the fractures induced by supercritical CO_(2) fracturing,this paper reconstructs the fracture surface of rock samples after supercritical CO_(2) fracturing using the laser morphological scanning technology,and establishes a model of proppant carrying and transport of supercritical CO_(2) in tortuous fractures on the basis of CFD-DEM method.In addition,the transport and placement characteristics of proppant in tortuous fractures are analyzed by comparing withflat fractures,and the effects of proppant density,injection rate of proppant carrying liquid,proppant concentration and other key parameters on proppant transport and distribution in fractures are investigated.And the following research results are obtained.First,compared with those inflat fractures,theflow paths of the proppant carrying supercritical CO_(2) liquid in tortuous fractures are tortuous and diverse,and the proppant presents strongerfluctuations and jumps laterally and vertically during its transport.Second,the proppant placement in tortuous fractures morphologically presents a wavy or even clustered non-uniform distribution.Third,low-density proppant has a better pass-ability in tortuous fractures,and the high injection rate can reduce the influence of tortuous fracture structure on proppant blocking.Fourth,if the concentration of injected proppant in the tortuous fracture is too low,good fracturing support effect cannot be achieved,and the optimal value under the simulation conditions in this paper is around 3%.In conclusion,the simulation results are of important theoretical and engineering significance to understanding the mechanism of proppant blocking in the pumping process of proppant carrying liquid for supercritical CO_(2) fracturing and optimizing thefield fracturing design.展开更多
Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methan...Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.展开更多
The impact toughness of EN-GJS-400-18-LT ductile iron was measured by Charpy V-notch impact test at temperature between-80 and 20℃.The fracture properties were tested under instrumented impact loading.Total impact fr...The impact toughness of EN-GJS-400-18-LT ductile iron was measured by Charpy V-notch impact test at temperature between-80 and 20℃.The fracture properties were tested under instrumented impact loading.Total impact fracture energy,crack initiation and propagation energy,dynamic loads and the ductile to brittle temperature were measured.Three-dimensional reconstruction of impact fracture morphology was accomplished by confocal laser scanning microscope.The results of quantitative fractography indicate that cleavage fracture produces flatter fracture surfaces accompanying with less absorbed energy during the impact fracture process.It indicates that fracture roughness has a close relationship with crack propagation energy at low temperature.展开更多
Brain regenerative studies require precise visualization of the morphological structures. However, few imaging methods can effectively detect the adult zebrafish brain in real time with high resolution and good penetr...Brain regenerative studies require precise visualization of the morphological structures. However, few imaging methods can effectively detect the adult zebrafish brain in real time with high resolution and good penetration depth. Long-term in vivo monitoring of brain injuries and brain regeneration on adult zebrafish is achieved in this study by using 1325 nm spectral-domain optical coherence tomography（SD-OCT）. The SD-OCT is able to noninvasively visualize the skull injury and brain lesion of adult zebrafish. Valuable phenomenon such as the fractured skull, swollen brain tissues, and part of the brain regeneration process can be conducted based on the SD-OCT images at different time points during a period of 43 days.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.42377143)Sichuan Natural Science Foundation (Grant No.2024NSFSC0097)the Open Fund of State Key Laboratory of Coal Mining and Clean Utilization,China (Grant No.2021-CMCU-KFZD001).
文摘In the concurrent extraction of coal and gas,the quantitative assessment of evolving characteristics in mining-induced fracture networks and mining-enhanced permeability within coal seams serves as the cornerstone for effective gas extraction.However,representing mining-induced fracture networks from a three-dimensional(3D)sight and developing a comprehensive model to evaluate the anisotropic mining-enhanced permeability characteristics still pose significant challenges.In this investigation,a field experiment was undertaken to systematically monitor the evolution of borehole fractures in the coal mass ahead of the mining face at the Pingdingshan Coal Mining Group in China.Using the testing data of borehole fracture,the mining-induced fracture network at varying distances from the mining face was reconstructed through a statistical reconstruction method.Additionally,utilizing fractal theory,a model for the permeability enhancement rate(PER)induced by mining was established.This model was employed to quantitatively depict the anisotropic evolution patterns of PER as the mining face advanced.The research conclusions are as follows:(1)The progression of the mining-induced fracture network can be classified into the stage of rapid growth,the stage of stable growth,and the stage of weak impact;(2)The PER of mining-induced fracture network exhibited a typical progression that can be characterized with slow growth,rapid growth and significant decline;(3)The anisotropic mining-enhanced permeability of the reconstructed mining-induced fracture networks were significant.The peak PER in the vertical direction of the coal seam is 6.86 times and 4446.38 times greater than the direction perpendicular to the vertical thickness and the direction parallel to the advancement of the mining face,respectively.This investigatione provides a viable approach and methodology for quantitatively assessing the anisotropic PER of fracture networks induced during mining,in the concurrent exploitation of coal and gas.
基金The National Natural Science Foundation of China(NSFC)has developed a“comprehensive experimental system for hydro-jet radial horizontal wells”(No.51827804)in the Major Scientific Research Instrument Development ProjectNSFC General Project of“Research on Sand Carrying Mechanism in Supercritical CO_(2)Fractures”(No.51874318)NSFC Outstanding Youth Science Fund Project OF“Oil and Gas Well Fluid Mechanics and Engineering”(No.51922107).
文摘Supercritical CO_(2) fracturing is an important development trend to reach the goal of"dual carbon"and avoid the problem that hydraulic fracturing is influenced by water resource.In order to clarify the transport characteristics of proppant in the fractures induced by supercritical CO_(2) fracturing,this paper reconstructs the fracture surface of rock samples after supercritical CO_(2) fracturing using the laser morphological scanning technology,and establishes a model of proppant carrying and transport of supercritical CO_(2) in tortuous fractures on the basis of CFD-DEM method.In addition,the transport and placement characteristics of proppant in tortuous fractures are analyzed by comparing withflat fractures,and the effects of proppant density,injection rate of proppant carrying liquid,proppant concentration and other key parameters on proppant transport and distribution in fractures are investigated.And the following research results are obtained.First,compared with those inflat fractures,theflow paths of the proppant carrying supercritical CO_(2) liquid in tortuous fractures are tortuous and diverse,and the proppant presents strongerfluctuations and jumps laterally and vertically during its transport.Second,the proppant placement in tortuous fractures morphologically presents a wavy or even clustered non-uniform distribution.Third,low-density proppant has a better pass-ability in tortuous fractures,and the high injection rate can reduce the influence of tortuous fracture structure on proppant blocking.Fourth,if the concentration of injected proppant in the tortuous fracture is too low,good fracturing support effect cannot be achieved,and the optimal value under the simulation conditions in this paper is around 3%.In conclusion,the simulation results are of important theoretical and engineering significance to understanding the mechanism of proppant blocking in the pumping process of proppant carrying liquid for supercritical CO_(2) fracturing and optimizing thefield fracturing design.
基金This study was supported by the China Geological Survey Projects(DD20160186,12120115008201)
文摘Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.
文摘The impact toughness of EN-GJS-400-18-LT ductile iron was measured by Charpy V-notch impact test at temperature between-80 and 20℃.The fracture properties were tested under instrumented impact loading.Total impact fracture energy,crack initiation and propagation energy,dynamic loads and the ductile to brittle temperature were measured.Three-dimensional reconstruction of impact fracture morphology was accomplished by confocal laser scanning microscope.The results of quantitative fractography indicate that cleavage fracture produces flatter fracture surfaces accompanying with less absorbed energy during the impact fracture process.It indicates that fracture roughness has a close relationship with crack propagation energy at low temperature.
基金supported by MYRG2014-00093-FHS,MYRG 2015-00036-FHS,and MYRG2016-00110-FHS grants from the University of Macao in MacaoFDCT026/2014/A1 and FDCT 025/2015/A1 grants from Macao government
文摘Brain regenerative studies require precise visualization of the morphological structures. However, few imaging methods can effectively detect the adult zebrafish brain in real time with high resolution and good penetration depth. Long-term in vivo monitoring of brain injuries and brain regeneration on adult zebrafish is achieved in this study by using 1325 nm spectral-domain optical coherence tomography（SD-OCT）. The SD-OCT is able to noninvasively visualize the skull injury and brain lesion of adult zebrafish. Valuable phenomenon such as the fractured skull, swollen brain tissues, and part of the brain regeneration process can be conducted based on the SD-OCT images at different time points during a period of 43 days.
