Pickering Emulsions Stabilized By AlOOH Nanoparticles And Amphiphiles For Enhanced Oil Recovery

The application of emulsions to enhanced oil recovery(EOR)has been extensively studied.However,traditional surfactant stabilized emulsions lack long-term stability,especially in harsh reservoir environments.In order to meet the requirements of tertiary oil recovery,it is necessary to investigate emulsion systems with long-term stability.Here,we studied the in situ hydrophobic modification of hydrophilic Al OOH nanoparticles via the adsorption of amphiphilic molecules and characterization of Pickering emulsions stabilized by amphiphilic molecules and nanoparticles under different conditions,and its application in EOR.The anionic surfactant sodium dodecylbenzene sulfonate(SDBS)and short-chain amphiphilic sodium benzene sulfonate(SBS)were used to in situ modify Al OOH nanoparticles.The adsorption of SDBS and SBS molecules on Al OOH nanoparticles was verified by FTIR,Zeta potential and contact angle experiments.The properties and stabilization mechanism of SDBS/Al OOH and SBS/Al OOH stabilized emulsions were studied by optical microscope,stability analyzer,and rheological experiments.The stability of the emulsion under the environment of high temperature and high electrolyte concentration,as well as the effect and mechanism of its application in water flooding reservoirs to improve oil recovery were further investigated.The results show that both SDBS and SBS can be adsorbed to the surface of Al OOH nanoparticles for hydrophobic modification.The difference is that SDBS molecules can form a double-layer adsorption on the surface of Al OOH nanoparticles,while SBS can only form a single-layer adsorption on the surface of Al OOH nanoparticles.This difference causes the hydrophobicity of SDBS-modified Al OOH nanoparticles to increase initially and then decrease with the increase of SDBS concentrations,while the hydrophobicity of SBS-modified Al OOH nanoparticles increases monotonously with the increase of SBS concentrations until reaches stability.This variation in hydrophobicity of SDBS-modified Al OOH nanoparticles directly leads to the double inversion of the emulsion type from the o/w to w/o and then back to o/w.Both SDBS/Al OOH and SBS/Al OOH stabilized emulsions show excellent long-term stability.This is because the modified Al OOH particles with enhanced hydrophobicity can be closely adsorbed on the oil/water interface to form a high-strength interfacial film and form threedimensional network structure between the emulsion droplets,which significantly improves the stability of the emulsion by inhibiting the movement and coherence of the emulsion droplets.The emulsion can maintain excellent stability even under conditions of high temperature and high electrolyte concentrations.Core flooding test and microscopic visualization experiment show that the Pickering emulsion can effectively improve the oil recovery of water flooding reservoirs.The EOR mechanism is mainly to expand the swept area by plugging the highpermeability channels.