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
The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineraliza...The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineralization of photocrosslinkable HA polymers through sol-gel synthesis.In this way,it has been possible to overcome some limitations due to classical approaches based on the physical blending of inorganic fillers into polymer matrix.To this aim,methacrylated and maleated HA,synthesized with similar degree of substitution(DS)were compared in terms of mechanical and physico-chemical properties.The success of in situ biomineralization was highlighted by reflect Fourier transform infrared spectroscopy and thermogravimetric analysis.Furthermore,mechanical characterization demonstrated the reinforcing effect of inorganic fillers evidencing a strong correlation with DS.The swelling behavior resulted to be correlated with filler concentration.Finally,the cytotoxicity tests revealed the absence of toxic components and an increase of cell proliferation over culture time was observed,highlighting these bio-nanocomposite hyaluronan derivatives as biocompatible hydrogel with tunable properties.展开更多
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.
基金the H2020-MSCA-RISE-2016,SECOND.R.I.,Grant Agreement No 734391Progetto Premiale di AREA SCIENCE PARK“OPEN LAB-A System of Open Research Facilities”for the support。
文摘The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineralization of photocrosslinkable HA polymers through sol-gel synthesis.In this way,it has been possible to overcome some limitations due to classical approaches based on the physical blending of inorganic fillers into polymer matrix.To this aim,methacrylated and maleated HA,synthesized with similar degree of substitution(DS)were compared in terms of mechanical and physico-chemical properties.The success of in situ biomineralization was highlighted by reflect Fourier transform infrared spectroscopy and thermogravimetric analysis.Furthermore,mechanical characterization demonstrated the reinforcing effect of inorganic fillers evidencing a strong correlation with DS.The swelling behavior resulted to be correlated with filler concentration.Finally,the cytotoxicity tests revealed the absence of toxic components and an increase of cell proliferation over culture time was observed,highlighting these bio-nanocomposite hyaluronan derivatives as biocompatible hydrogel with tunable properties.
