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Abstract:
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The petroleum industry has been utilizing surfactant stabilized foams for mobility control and enhanced oil recovery applications . However , if surface -treated nanoparticles were utilized instead of surfactants , the foams could have a number of important advantages . The solid -stabilized foams are known to have a much better stability than the surfactant -stabilized foams , because the energy required to bring nanoparticles to , and detach from the foam bubble surface is much larger than that of surfactants , and thus the resulting foam will be more stable . Since nanoparticles are the stabilizing component of the foam and are solid , they have potential to stabilize foam at high temperature conditions for extended periods of time . Since they are inherently small , nanoparticles , as well as the foam that they stabilize , can be transported through rocks without causing plugging in pore throats .
Stable supercritical carbon dioxide -in -water foams were created using 5 nm silica -core nanoparticles whose surface had short polyethylene -glycol chains covalently bonded to it . The foams were made by injecting CO2 and an dispersion of with surface -treated nanoparticles simultaneously through a glass -bead pack . The fluids flowing through this permeable media created shear rates of about 1350 sec -1 . Nanoparticle concentration , nanoparticle coating , water salinity , volume ratios between CO2 and water , temperature and shear rates were systematically varied in order to define the range of conditions for foam generation . Using de -ionized water to dilute the nanoparticle concentration , we were able to generate stable foams were at nanoparticle concentrations as low as 0 .05 weight percent . Among the different surface coatings that we tested PEG coatings were the only type that was able to stabilize foam . As the salinity of the aqueous phase increased , the nanoparticle concentration required to maintain foam also increased ; for example , 0 .5 weight percent nanoparticles were required for 4 weight percent NaCl brine . Foam stability was weakly correlated with volume ratios as foams were made across ratios from two to fourteen , and the normalized viscosity ratio increased with the increase of the phase ratio . Foams were created at temperatures up to 95 degrees Celsius . Foam generation was also determined to require a critical shear rate , which increased with temperature . When foam was stabilized by the nanoparticles , the foam exhibited an increase of between two and twenty times in the resistance of flow compared to the two fluids flowing without nanoparticles . |