Abstract:

To address the technical challenges of poor thermal stability and inadequate mobility control for using profile-control and flooding systems based on emulsions in high-temperature and high-salinity heavy oil reservoirs, in this work, a novel temperature-and salt-resistant nanoparticle-stabilized emulsion system was constructed for profile control and flooding, in which nano-SiO₂ particles were modified by using lauramidopropylamine oxide（OA）. The experimental results showed that, when the modification was carried out at an OA content of 0.05%, the constructed emulsion system exhibited good environmental adaptability, maintaining stability for over 30 days under harsh conditions of 90 ℃ and of salinity of 2×10⁵ mg/L. Rheological characterization showed that the system had obvious shear-thinning behavior with a viscosity recovery reaching 85.4%. Dynamic rheological analysis confirmed that the three-dimensional network structure formed by nanoparticles in aqueous phase was the key factor endowing the system with characteristics of elastic fluids. Core flooding experiments verified the excellent plugging performance of this system across a wide permeability range（50×10^-3-3 500×10^-3 μm², with resistance factor > 80）. Particularly in heterogeneous parallel-core experiments with permeability contrast of 4, the oil recovery was increased by 30.2%, the fractional flow rate was improved by over 40%, and both sweep efficiency and ultimate oil recovery were significantly enhanced.

Key words: high-temperature and high-salinity reservoir, modified nano-SiO₂, emulsion flooding, rheological property, enhanced oil recovery