Examining the Dynamic Stability of Pickering Emulsions during Flow through Porous Media
Abstract
Recent developments in nanotechnology have increased focus on nanoparticle-stabilized Pickering macro-emulsions (emulsions with droplet diameters greater than 1 μm) as potential agents for enhanced oil recovery, contaminated aquifer treatment, and other applications involving transport through porous media. The behavior of Pickering emulsions in porous media is poorly understood, with most research focusing on static stability and neglecting dynamic behavior. This work describes a series of core-floods performed to measure the dynamic stability of decane-in-brine Pickering emulsions stabilized using silica nanoparticles coated with polyethylene glycol (PEG) at various nanoparticle concentrations. Brine and decane mixtures were emulsified in batches with sonification and injected at constant flow rate into a Boise sandstone core. Emulsion droplets at the inlet and outlet were imaged, effluent was collected, and the pressure drop across the core was recorded. Emulsion viscosity and static coalescence pressure were measured in a rheometer and centrifuge, respectively. The uploaded figure plots pressure behavior of selected core-floods.
Emulsions generated with a greater concentration of nanoparticles required higher pressures to flow through the core, with the exception of the 5 wt% emulsions, which both collapsed partway into the core-flood. Less concentrated emulsions produced larger droplets, more frequent pressure oscillations, and coalesced in greater proportions, with 2 wt% being the critical concentration necessary to produce strong emulsion in some proportion in the effluent. The 2 wt% threshold and emulsion collapse at higher concentrations are supported by prior work observing emulsion flow through slim tubes. These results together support a mechanism describing emulsion flow in terms of static coalescence and "breakthrough" pressures, wherein the coalescence pressure (the pressure drop of coalescence as measured in a centrifuge) must be larger than the breakthrough pressure (the pressure drop necessary to drive the emulsion through the core) in order for the emulsion to remain stable during flow. The relationship between these pressures may be combined with predictions of capillary forces during emulsion flow in porous media to better understand dynamic emulsion stability.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H13R2007H
- Keywords:
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- 1805 Computational hydrology;
- HYDROLOGY;
- 1832 Groundwater transport;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY