Porous media flooding mechanism of nanoparticle-enhanced emulsification system

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Abstract
This study carried out interfacial tension (IFT) test, sand surface element analysis and scanning electron microscope (SEM) image, rock-oil-emulsification system interaction test, microstructure, droplet size distribution and stability of oil in water (O/W) emulsion to clarify the porous media flooding mechanism of hydrophilic Nano-SiO2 enhanced emulsification system. Results shows that by adding small amount of Nano-SiO2 (0.01 wt.%) into anionic surfactant fatty alcohol polyoxyethylene ether sodium hydroxypropyl sulfonate (AEOSHS) solution (0.5 wt.%), the IFT of oil-water effectively reduced, the adsorption loss of AEOSHS on the formation sand surface was reduced by more than 70%, the droplet size of formed O/W emulsion reduced by 50%. This greatly improves the effective concentration of AEOSHS and emulsify heavy oil ability in formation away from injection well. Moreover, the spreading ability of oil on core surface is greatly reduced, and the width of diffusion zone is narrowed. Meanwhile, a very clear dividing line of oil can be seen which shows that the wettability of core has changed to water wet. The stability of formed O/W emulsion was further enhanced, and the coalescence and migration process of droplet is extremely slow. The oil recovery of AEOSHS+ Nano-SiO2 system can effectively increase 21.95% of original oil in place (OOIP). Both the sand-packed tube experiment and the microscopic visual oil flooding experiment show that the system can not only expand the sweep volume, but also improve the oil displacement efficiency, which means that the combination system can significantly improve the oil displacement effect.
Funding Information
  • National Key Transform Program (2016ZX05058-003-007)
  • National Natural Science Foundation of China (52174032, 51474227)
  • Shaanxi Key Research and Development Program (2021GY-112)

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