Nanoparticle-stabilized natural gas liquid emulsions for heavy oil recovery




Griffith, Nicholas Daniel

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The transport of nanoparticle-stabilized emulsions through porous media and its effects on enhanced oil recovery are only marginally understood. This thesis explores the characteristics of nanoparticle-stabilized emulsion flow in porous media, especially in respect to its residual oil recovery capabilities. Widely available, low-cost natural gas liquids were emulsified in brines using polyethylene glycol-coated silica nanoparticles. Emulsions with various aqueous nanoparticle phases and oil phases were generated via beadpack co-injection or sonication at varying salinities for observations of emulsion characteristics. In general it was found that high-salinity emulsions generated via sonication were more robust: statically and dynamically more stable than their lower salinity counterparts. Emulsions generated via beadpack co-injection displayed non-Newtonian shear-thinning rheology and larger droplet sizes. Emulsions generated via sonication displayed Newtonian rheology and much smaller droplet sizes. Coreflood experiments were conducted to assess the effects of different emulsion properties on residual oil recovery of heavy oils, effective permeability reduction capabilities (i.e. conformance control), and in-situ emulsion stability. During low salinity emulsion floods, no emulsion was produced in the effluent. However, by increasing the salinity, emulsion was produced in the effluent and up to 89% residual mineral oil was recovered at low injection rates (~16 ft/day). Increases in residual oil recovery during high salinity floods can be explained by DLVO and Filtration theory. By increasing the ionic concentration, the magnitude of repulsive electrostatic double layer forces are decreased, leading to increased droplet interception on grain surfaces. This results in more efficient droplet-pore throat blockage, therefore, redirecting displacing fluids into less permeable zones. Increasing the magnitude of the zeta-potential of injected emulsions resulted in marginal increases in oil recovery, significant reductions in effective permeability, and in-situ emulsion stability. It was concluded that at high zeta-potentials, emulsion droplets are likely repulsed via electrostatic repulsive forces rather than through mechanical bridging of aggregates between droplets, as observed in high salinity emulsions. The increase in permeability reduction in the high zeta-potential case occurs due to the droplets’ increased resistance to flow through a pore throat, a product of increased repulsive forces between droplets and grains encountered at tight constrictions


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