Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program...Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program has been established to demonstrate and understand the physics of laser direct drive.The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and lasereplasma interaction and coupling physics at the MJ scale at the National Ignition Facility.This article will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.展开更多
Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numer...Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.展开更多
文摘Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program has been established to demonstrate and understand the physics of laser direct drive.The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and lasereplasma interaction and coupling physics at the MJ scale at the National Ignition Facility.This article will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.
基金The work reported here is funded by Australian Coal Industry’s Research Program(ACARP)grant no.C26063.
文摘Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.
