Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level...Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level through numerical simulations are permitted.Molecular dynamics(MD)simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects.However,the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures.Thus,it is a big challenge for the beginners in this community to choose a proper method to start their investigations.In this review,we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids.A comprehensive comparison was made between the advantages and disadvantages of these typical techniques.We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing.It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.展开更多
A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were anal...A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.展开更多
Background: There has been a rapid global development of the horizontal drilling and hydraulic fracturing process termed fracking. This involves the dispersion of “produced water” which contains naturally occurring ...Background: There has been a rapid global development of the horizontal drilling and hydraulic fracturing process termed fracking. This involves the dispersion of “produced water” which contains naturally occurring radioactive material (NORM) which may contaminate surface water and pose a health risk. Objectives: To investigate association between early (0-28 days) infant mortality by county in Pennsylvania and fracking. Methods: We compared early infant mortality for 2007-2010 after fracking developed with a control period 2003-2006, contrasting a group of the 10 most heavily fracked counties with the rest of Pennsylvania. Results: Whilst early infant deaths decreased by 2.4% in the State over the period, in the 82,558 births in the 10 fracked counties there was a significant increase in mortality (238 vs 193;RR = 1.29;95% CI 1.05, 1.55;p = 0.011). For the five north east fracked counties Bradford, Susquehanna, Lycoming, Wyoming and Tioga the combined early infant mortality increased from 34 deaths to 60 (RR 1.66;1.05, 2.51;p = 0.014), whereas in the south western 5 counties Washington, Westmoreland, Fayette, Butler and Greene the increase was modest, 157 to 178 (RR 1.18;0.95, 1.46;p = 0.13). Increased risk was associated with exposure to groundwater, expressed as the county ratio of water wells divided by the number of births. Conclusions: Fracking appears to be associated with early infant mortality in populations living in counties where the process is carried out. There is some evidence that the effect is associated with private water well density and/or environmental law violations.展开更多
The increase in natural gas production in North America resulting from the implementation of new technologies related to the fracturing (fracking) of natural gas-bearing shale reservoirs has enhanced the security of s...The increase in natural gas production in North America resulting from the implementation of new technologies related to the fracturing (fracking) of natural gas-bearing shale reservoirs has enhanced the security of supply and lowered energy costs in the continent. Yet the environmental impact associated with shale gas development has raised concerns and debate among energy and environmental policy makers as to how best to address these concerns. As Canada’s largest producer of natural gas, the Province of Alberta is an example of a jurisdiction with numerous regulations for dealing with such environmental risks. This paper applies the CO/RE model of Konschnik and Bolingin examining Alberta’s environmental regulatory framework and the impact;it will have on further shale gas production in the province. Aside from the identification of risks associated with increased seismicity, the results of this examination suggest that the current regulatory environment does not appear to have any adverse effect on current and future shale gas production within the province. Furthermore, Alberta’s environmental regulation has influenced shale gas producers to pursue innovation in technology and engineering practice and has helped establish a collaborative approach to mitigating environmental risk.展开更多
The development of unconventional gas exploration in the USA, in particular shale gas, caused a revolution in the American and the global gas markets. The regional-wide use of unconventional gas resources could stabil...The development of unconventional gas exploration in the USA, in particular shale gas, caused a revolution in the American and the global gas markets. The regional-wide use of unconventional gas resources could stabilize the natural gas demand and the energy supply security of European and Asian countries. But traditionally, almost all gas contracts in Europe and Asia are linked to oil because of the demand for stable, long-term contracts. Furthermore, in many Asian countries, large state-owned enterprises dominate their national gas markets, leading to little competition and incentives to reduce gas prices. In Europe, the expansion of unconventional gas is facing grassroots opposition from environmental groups who are concerned about ground water safety, adequate waste water management, seismic events and greenhouse gas emissions. In this article, I will discuss the rapidly changing natural gas markets and the role and prospects of unconventional gas as well as its environmental impacts and unsustainability in industry level.展开更多
Workers involved in hydraulic fracking processes are exposed to various types of chemicals and dusts in their workplaces, such as proppants, which hold open the fissures created in the fracking process. Recently, cera...Workers involved in hydraulic fracking processes are exposed to various types of chemicals and dusts in their workplaces, such as proppants, which hold open the fissures created in the fracking process. Recently, ceramic proppants have been developed that may be less hazardous to workers than traditional proppants. Pulmonary function testing of workers producing ceramic proppant was used to assess the potential inhalation hazards of ceramic proppant. 100 male workers from a producer of ceramic proppant were evaluated with pulmonary function test data collected and evaluated using The American Thoracic Society (ATS) acceptability criteria. A comparison group was selected from the Third National Health and Nutrition Examination Survey (NHANES III) spirometry laboratory subset. No pulmonary function deficits were found in the worker group in comparison to the NHANES III population. Mean FEV1 and FVC values in workers were 3.8 and 4.8 liters respectively, and were greater as compared to the NHANES III population of similar demographics. An FEV1/FVC ratio of less than 0.8, when compared to the NHANES III group, produced an odds ratio of 0.44 in worker group, indicating less risk of preclinical pulmonary dysfunction. Overall, exposure to ceramic proppant was not found to produce an adverse impact on pulmonary function in workers engaged in the manufacture of ceramic proppant.展开更多
A series of gas inrush events occurred during development at Grosvenor Mine resulting in exposure to elevated levels of methane at the production face.A total of 22 gas inrush events occurred,with between 15 and 130 m...A series of gas inrush events occurred during development at Grosvenor Mine resulting in exposure to elevated levels of methane at the production face.A total of 22 gas inrush events occurred,with between 15 and 130 m3 of methane released during each event.The presence of an undrained seam in the immediate floor,geotechnical characteristics of the floor,and the stress environment all contributed to these dynamic floor events,while the geological characteristics of the seam below,such as the seam thickness and ash content of 75%,prevented effective predrainage.However,events only occurred in headings mined parallel to the principal horizontal stress direction.In cut-throughs(C/T)perpendicular to the principal stress direction no events occurred,and higher methane levels were observed at the production face.The solution to preventing the gas inrush events involved creating a conduit in the interburden between the mined seam and the seam in the immediate floor to allow the gas to be drained during the development of the headings,as occurred in the cut-throughs(cut-through and cross-cut are regional terms that are analogous).A series of underground inseam(UIS)holes were drilled using the directional drill rig with the aim of fracturing this interburden ahead of the face and promote floor failure to allow the gas to release consistently.The floor fracturing was conducted using water pressure generated from a longwall salvage pump,with the current UIS drilling equipment retrofitted with a series of subs,packers and a fracturing tool.The packers and the fracturing tool were shifted to desired locations along the drilled UIS borehole to achieve the required fracture.The fractures were monitored using a proving hole and with a HYDAC data logger attached to the salvage pack,with the results analysed on the surface to ensure connectivity to the working seam.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11372313,11002011 and 11202213)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M01)+1 种基金the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.Y2010031)the Fundamental Research Funds for the Central Universities and the Beijing Higher Education Young Elite Teacher Project
文摘Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level through numerical simulations are permitted.Molecular dynamics(MD)simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects.However,the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures.Thus,it is a big challenge for the beginners in this community to choose a proper method to start their investigations.In this review,we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids.A comprehensive comparison was made between the advantages and disadvantages of these typical techniques.We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing.It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.
基金supported by the National Natural Science Foundation of China(Nos.51374258,51504046,51404045)Program for Changjiang Scholars and Innovative Research Team in University of China(No.IRT13043)the National Basic Research Program of China(No.2014CB239206)
文摘A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.
文摘Background: There has been a rapid global development of the horizontal drilling and hydraulic fracturing process termed fracking. This involves the dispersion of “produced water” which contains naturally occurring radioactive material (NORM) which may contaminate surface water and pose a health risk. Objectives: To investigate association between early (0-28 days) infant mortality by county in Pennsylvania and fracking. Methods: We compared early infant mortality for 2007-2010 after fracking developed with a control period 2003-2006, contrasting a group of the 10 most heavily fracked counties with the rest of Pennsylvania. Results: Whilst early infant deaths decreased by 2.4% in the State over the period, in the 82,558 births in the 10 fracked counties there was a significant increase in mortality (238 vs 193;RR = 1.29;95% CI 1.05, 1.55;p = 0.011). For the five north east fracked counties Bradford, Susquehanna, Lycoming, Wyoming and Tioga the combined early infant mortality increased from 34 deaths to 60 (RR 1.66;1.05, 2.51;p = 0.014), whereas in the south western 5 counties Washington, Westmoreland, Fayette, Butler and Greene the increase was modest, 157 to 178 (RR 1.18;0.95, 1.46;p = 0.13). Increased risk was associated with exposure to groundwater, expressed as the county ratio of water wells divided by the number of births. Conclusions: Fracking appears to be associated with early infant mortality in populations living in counties where the process is carried out. There is some evidence that the effect is associated with private water well density and/or environmental law violations.
文摘The increase in natural gas production in North America resulting from the implementation of new technologies related to the fracturing (fracking) of natural gas-bearing shale reservoirs has enhanced the security of supply and lowered energy costs in the continent. Yet the environmental impact associated with shale gas development has raised concerns and debate among energy and environmental policy makers as to how best to address these concerns. As Canada’s largest producer of natural gas, the Province of Alberta is an example of a jurisdiction with numerous regulations for dealing with such environmental risks. This paper applies the CO/RE model of Konschnik and Bolingin examining Alberta’s environmental regulatory framework and the impact;it will have on further shale gas production in the province. Aside from the identification of risks associated with increased seismicity, the results of this examination suggest that the current regulatory environment does not appear to have any adverse effect on current and future shale gas production within the province. Furthermore, Alberta’s environmental regulation has influenced shale gas producers to pursue innovation in technology and engineering practice and has helped establish a collaborative approach to mitigating environmental risk.
文摘The development of unconventional gas exploration in the USA, in particular shale gas, caused a revolution in the American and the global gas markets. The regional-wide use of unconventional gas resources could stabilize the natural gas demand and the energy supply security of European and Asian countries. But traditionally, almost all gas contracts in Europe and Asia are linked to oil because of the demand for stable, long-term contracts. Furthermore, in many Asian countries, large state-owned enterprises dominate their national gas markets, leading to little competition and incentives to reduce gas prices. In Europe, the expansion of unconventional gas is facing grassroots opposition from environmental groups who are concerned about ground water safety, adequate waste water management, seismic events and greenhouse gas emissions. In this article, I will discuss the rapidly changing natural gas markets and the role and prospects of unconventional gas as well as its environmental impacts and unsustainability in industry level.
文摘Workers involved in hydraulic fracking processes are exposed to various types of chemicals and dusts in their workplaces, such as proppants, which hold open the fissures created in the fracking process. Recently, ceramic proppants have been developed that may be less hazardous to workers than traditional proppants. Pulmonary function testing of workers producing ceramic proppant was used to assess the potential inhalation hazards of ceramic proppant. 100 male workers from a producer of ceramic proppant were evaluated with pulmonary function test data collected and evaluated using The American Thoracic Society (ATS) acceptability criteria. A comparison group was selected from the Third National Health and Nutrition Examination Survey (NHANES III) spirometry laboratory subset. No pulmonary function deficits were found in the worker group in comparison to the NHANES III population. Mean FEV1 and FVC values in workers were 3.8 and 4.8 liters respectively, and were greater as compared to the NHANES III population of similar demographics. An FEV1/FVC ratio of less than 0.8, when compared to the NHANES III group, produced an odds ratio of 0.44 in worker group, indicating less risk of preclinical pulmonary dysfunction. Overall, exposure to ceramic proppant was not found to produce an adverse impact on pulmonary function in workers engaged in the manufacture of ceramic proppant.
基金The authors thank Anglo American for supporting this work and for permission to publish this paper.Also acknowledge Trent Griffiths Griffiths,Rob Nowell and Gary Needham’s assistance in developing the concept and strategy.In addition,Raymond Kostowski for managing the project and the RADCO team for operating the drilling and fracturing equipment.
文摘A series of gas inrush events occurred during development at Grosvenor Mine resulting in exposure to elevated levels of methane at the production face.A total of 22 gas inrush events occurred,with between 15 and 130 m3 of methane released during each event.The presence of an undrained seam in the immediate floor,geotechnical characteristics of the floor,and the stress environment all contributed to these dynamic floor events,while the geological characteristics of the seam below,such as the seam thickness and ash content of 75%,prevented effective predrainage.However,events only occurred in headings mined parallel to the principal horizontal stress direction.In cut-throughs(C/T)perpendicular to the principal stress direction no events occurred,and higher methane levels were observed at the production face.The solution to preventing the gas inrush events involved creating a conduit in the interburden between the mined seam and the seam in the immediate floor to allow the gas to be drained during the development of the headings,as occurred in the cut-throughs(cut-through and cross-cut are regional terms that are analogous).A series of underground inseam(UIS)holes were drilled using the directional drill rig with the aim of fracturing this interburden ahead of the face and promote floor failure to allow the gas to release consistently.The floor fracturing was conducted using water pressure generated from a longwall salvage pump,with the current UIS drilling equipment retrofitted with a series of subs,packers and a fracturing tool.The packers and the fracturing tool were shifted to desired locations along the drilled UIS borehole to achieve the required fracture.The fractures were monitored using a proving hole and with a HYDAC data logger attached to the salvage pack,with the results analysed on the surface to ensure connectivity to the working seam.
