Water-in-carbon dioxide emulsions stabilized with hydrophobic silica particles

Abstract

W/C emulsions were stabilized using hydrophobic silica particles adsorbed at the interface, resulting in average droplet diameters as low as 7.5 microm. A porous cross-linked shell was formed about a hydrophilic (colloidal and fumed) silica core with a trifunctional silylating agent, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethyoxysilane, to render the particles CO(2)-philic. The stability of emulsions comprising equal weights of CO(2) and water was assessed with visual observations of settling fronts and the degree of emulsion coalescence, and the average drop size was measured by optical microscopy. The effect of CO(2) density on both emulsion stability and droplet size was determined quantitatively. The major destabilizing mechanism of the emulsions was settling, whereas Ostwald ripening and coalescence were not visible at any density, even over 7 days. Flocculation of the settling droplets did not occur, although gelation of the emulsions through particle interactions resulted after longer periods of time. CO(2)-philic particles offer a new route to highly stable W/C emulsions, with particle energies of attachment on the order of 10(6)kT, even at CO(2) densities as low as 0.78 g ml(-1). At these low densities, surfactants rarely stabilize emulsions as the result of poor surfactant tail solvation.

Application of Nanoparticles in Enhanced Oil Recovery: A Critical Review of Recent Progress

“…Images obtained by an optical microscope showed that the uniform size of the NPs generate a compact, well-structured monolayer at the aqueous/non-aqueous phase interface to make the emulsion extremely stable even under high temperatures ( Figure 13) [16]. In addition to generate w/o or o/w emulsions by using NPs, the silica NPs can be used to stabilize supercritical CO2-in-water emulsion, and water-in-supercritical CO2 emulsion [63,64]. These nanoemulsions can be used for improving oil recovery, especially for CO2 flooding or CO2 sequestration because they can maintain stable under harsh reservoir conditions (high temperatures, pressures, shear and salinity).…”

“…These reactions are called aquathermolysis. The presence of nanocatalysts, such as nickel and iron, catalyzes the breaking of carbon-sulfur bonds within asphaltenes, increasing saturates and aromatics in the heavy oil, which can be described as follows [68]: In addition to generate w/o or o/w emulsions by using NPs, the silica NPs can be used to stabilize supercritical CO 2 -in-water emulsion, and water-in-supercritical CO 2 emulsion [63,64]. These nanoemulsions can be used for improving oil recovery, especially for CO 2 flooding or CO 2 sequestration because they can maintain stable under harsh reservoir conditions (high temperatures, pressures, shear and salinity).…”

Performance improvement of ionic surfactant flooding in carbonate rock samples by use of nanoparticles

“…Another property of nanoparticles is their high ability to stabilize oil-in-water emulsions, and the nanoemulsions can travel for a long distance in reservoirs without much retention (Kong and Ohadi 2010). In addition, nanoparticles can stabilize emulsions of supercritical CO 2 in water and emulsions of water in supercritical CO 2 (Dickson et al 2004;Adkins et al 2007). Kanj et al (2009) investigated the transport of nanoparticles in porous media and estimated the optimum size of nanoparticles effectively used in reservoir rocks.…”

Action of hydrotropes in water-in-CO2 microemulsions

“…20. 10 The data have been analysed by the fitting program SASview using a built-in spherical core- 11 shell form factor model. 27,28 The scattering laws used can be found in Supporting 12 information, the SLD of the water core and CO2 bulk were calculated from their 13 compositions and constrained for the purposes of fitting (with 30 wt% D2O and 70 wt% H2O,…”