(152c) The Influence of Surfactants and Nanoparticles on Hydrate Formation in Water-in-Oil Emulsions

Clathrate hydrates are non-stoichiometric, ice-like crystalline solids that can lead to plugging of crude oil pipelines. Crude oil is a complex hydrocarbon mixture that includes asphaltenes, aromatics, naphthenes, resins, and paraffins. Although, the effect of nanoparticles and surfactants on hydrate formation has been investigated, the synergistic effects of surfactant and nanoparticles on hydrate formation are not well understood. Elucidating the synergistic effects of surfactants and nanoparticles on hydrate formation would improve the hydrate prediction strategies.

A fundamental investigation using model oil was carried out to determine the effect of interactions between silica nanoparticles and surfactants on hydrate formation in water-in-oil emulsions. Cyclopentane was used as the hydrate-forming component. A DHR-3 stress controlled rheometer was used to examine the rheological behavior of hydrate forming emulsions. In order to elucidate the importance of rheometer geometries, rheological behavior of hydrate slurries using standard (concentric cylinder) and non-standard (vane and helical ribbon) geometries was quantified. An Olympus BX53 polarized optical microscope was used to quantify droplet size distribution.

In addition to the wettability of nanoparticles, the mode of addition of nanoparticles played a critical role in determining the droplet size of emulsions, flow behavior of emulsions and hydrate induction times. Partially hydrophobic nanoparticles enhanced hydrate formation as compared to highly hydrophobic nanoparticles upon the addition of nanoparticles to surfactant containing oil phase before emulsion formation (pre-mixing). On the contrary, partially hydrophobic nanoparticles delayed hydrate formation as compared to highly hydrophobic nanoparticles upon the addition of nanoparticles to surfactant stabilized water-in-oil emulsions (post-mixing). Confocal microscopy was used to determine the spatial distribution of nanoparticles. Furthermore, interfacial tension experiments were performed in order to understand the surfactant-nanoparticles interactions at the oil-water interface.