Nanoparticles for Oil Dispersants and Nano Tracers
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Nanoparticles are promising candidates to improve the efficiency of various activities in oil and gas industry such as reservoir characterization, enhanced oil recovery, and oil dispersion due to their large surface area, interfacial activity, and tunable chemical properties. In this dissertation, the potential of surface modified inorganic nanoparticles as oil dispersants and nanosensors were examined and their behaviors were investigated. Silica nanoparticles with hydrophilic poly(oligo(ethylene oxide) monomethyl ether methacrylate) (POEOMA) homopolymer brushes were tested as oil dispersants. These hybrid nanoparticles successfully reduced hexane – water interfacial tension at low nanoparticle concentrations and oil – water emulsions formed using the nanoparticles were stable for more than 60 days. To increase interfacial activity, hydrophilic polystyrene (PS) chains were extended from the homopolymer grafted nanoparticles and synthesized amphiphilic P(OEOMA-b-sty) block copolymer grafted nanoparticles. The copolymer grafted nanoparticles presented improved interfacial activity and oil dispersion capacity. Oil – water emulsions formed by the copolymer grafted nanoparticles showed excellent stability and became solidified hard emulsions after 10 days. For both homopolymer and copolymer grafted particles, hydrodynamic diameters were the key parameter to determine their efficiency as oil dispersants. Cryo-scanning electron microscopy was used to investigate the behavior of the hybrid nanoparticles at oil – water interfaces and the micrographs showed the segregation of the hybrid nanoparticles and their unique void-compensating behavior. Transport behavior of negatively charged carbon nanoparticles in porous rock cores was also examined using single phase core flooding experiments and 1-dimesional convection-dispersion equation. Temperature dependence of transport parameters such as dispersion coefficients and retardation factors were evaluated. The retardation factors were inversely proportional to the rock permeabilities due to particle retention effects. Florescence microscopy revealed that the carbon nanoparticles were preferentially absorbed on the carbonate rock rather than the sandstone rock due to the surface charge effects.