Nanoparticle and Surfactant Oil/Water Emulsions - Is Different Treatment Required?

Abstract Experimental observations regarding the formation of oil-water emulsions stabilized by nanoparticles and surfactants during oil production operations are presented. Similarities and differences between the two types of emulsions are discussed based on acquired separation profiles, as well as respective fluid interfacial properties. A state-of-the-art, portable Dispersion Characterization Rig (P- DCR) is used to run the experiments and a surveillance camera is deployed to monitor emulsion separation kinetics. Commercial grade mineral oil and distilled water are used as the test fluids. Silica nanoparticles of different wettability and surfactants with different HLB values are deployed to investigate commonalities/differences between surfactant and nanoparticle stabilized emulsions. Separation profiles were analyzed and similar behavior between the corresponding surfactant and nanoparticle emulsions was observed for the 25% water-cut case. For higher water-cuts, however, the surfactant stabilized emulsions were tighter than their nanoparticle counterparts, displaying much lower separation rates. In the most severe cases, the surfactants totally inhibited the oil creaming process and oil remained trapped in the emulsion for several hours. Multiple emulsions (O/W/O) were observed in certain cases (for hydrophilic nanoparticles and lipophilic surfactants (Span 80)). It appears, based on the aforementioned experimental observations, that the presence of surfactants can cause more severe problems to the oil-water separation process than the presence of an equal concentration of nanoparticles. Pendant drop measurements indicate that the surfactants can lower the interfacial tension between oil and water significantly, whereas the nanoparticles do not have a similar effect. Current research sets the basis for more thorough investigations aimed at providing guidelines for more efficient operation of separators handling surfactant or nanoparticle stabilized emulsions and better understanding of related phenomena.