Interaction between Surfactants and SiO2 Nanoparticles in Multiphase Foam and Its Plugging Ability

To improve the stability of foam fluids, SiO2 nanoparticles and trace amount of Gemini cationic surfactant were combined with the main foaming agent, nonionic surfactant, to form a tricomponent multiphase foam. The stability of the multiphase foam was assessed through two parameters of half-life time and dilational modulus. The interaction between surfactants and nanoparticles were studied though surface tension, adsorption amount, and ζ potential measurement. The effects of saline ions and temperature on foam stability were also investigated. The plugging ability of the tricomponent multiphase foam was assessed using a sandpack model. The optimized tricomponent multiphase foam was 10 times more stable than corresponding foam without nanoparticles in terms of half-life time and also resisted to saline and temperature to a certain degree because the adsorption of nanoparticles at the interface improved the mechanic strength of foam film. The tricomponent multiphase foam showed more excellent plugging ability in porous media than foam without nanoparticles during flooding. The adsorption of cationic surfactant not only changed the surface hydrophobicity of the SiO2 nanoparticles, but also promoted the adsorption of APG molecules. Combined the results of Gemini C12C3C12Br2 replaced by CTAB or SDS, and C12C3C12Br2/SiO2 replaced by pretreated partially hydrophobic SiO2 nanoparticle (H15), it is deduced that the in situ surface modification by cationic adsorption to a suitable hydrophobicity was a key step in multiphase stability. Compared with the pretreated partially hydrophobic SiO2 nanoparticle, more SiO2 nanoparticles were distributed at the air/liquid interface and utilized effectively in the tricomponent multiphase foam.