Polymeric nanoparticle suspension is a newly developed oil-displacing agent for enhanced oil recovery (EOR) in low-permeability reservoirs. In this work, SiO₂/P(MBAAm-co-AM) polymeric nanoparticles were successfully synthesized by a simple distillation-precipitation polymerization method. Due to the introduction of polymer, the SiO₂/P(MBAAm-co-AM) nanoparticles show a favorable swelling performance in aqueous solution, and their particle sizes increase from 631 to 1258 nm as the swelling times increase from 24 to 120 h. The apparent viscosity of SiO₂/P(MBAAm-co-AM) suspension increases with an increase of mass concentration and swelling time, whereas it decreases as the salinity and temperature increase. The SiO₂/P(MBAAm-co-AM) suspension behaves like a non-Newtonian fluid at lower shear rates, yet like a Newtonian fluid at shear rates greater than 300 s-1. The EOR tests of the SiO₂/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability cores show that SiO₂/P(MBAAm-co-AM) nanoparticles can effectively improve the sweep efficiency and recover more residual oils. A high permeability ratio can result in a high incremental oil recovery in parallel cores. With an increase of the permeability ratio of parallel cores from 1.40 to 15.49, the ratios of incremental oil recoveries (low permeability/high permeability) change from 7.69/4.61 to 23.61/8.46. This work demonstrates that this SiO₂/P(MBAAm-co-AM) suspension is an excellent conformance control agent for EOR in heterogeneous, low-permeability reservoirs. The findings of this study can help to further the understanding of the mechanisms of EOR using SiO₂/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability reservoirs.
Keywords: core-shell polymeric nanoparticles; enhanced oil recovery; heterogeneous reservoir; permeability ratio; suspension.