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.

The transformation process of α-Fe₂O₃ to cubic Fe₃O₄ through “dissolution–reduction–recrystallization”.

The shape evolution of spinel-structured Fe₃O₄was systematically investigated using a one-pot solvothermal route. Using FeCl₃·6H₂O as the precursor, triangular and hexagonal plates, octahedrons, dodecahedrons, and spherical Fe₃O₄were obtained by selecting the adequate ration of NaOH, N₂H₄·H₂O, Fe³⁺, and EDTA. The slow nucleation and growth rate favor the formation of low energy plate-like products, and the spherical crystals are obtained as the result of extremely fast nucleation and growth rate. It is also suggested that the generating rate of Fe(II) reduced from Fe(III) probably affects the growth speed along different facets, further influencing the final size and shape of the produced crystals.

A series of Ce_1−XSn_XO₂ (X = 0, 0.2, 0.3, 0.4, 0.5, 0.9, 1) catalysts were synthesized via the combustion method. The physical and chemical structures of the prepared catalysts were systematically characterized by XRD, BET, SEM, TEM, XPS, and TPR. The Ce_1−XSn_XO₂ catalysts have higher catalytic activities than the mono-oxide catalysts, as there are synergistic effects between CeO₂ and SnO₂. The catalytic activities of the Ce_1−XSn_XO₂ catalysts are dependent on the X for the catalytic combustion of ethyl acetate (EA). The Ce_1−XSn_XO₂ (X < 0.5) catalysts show high catalytic performances. Meanwhile, the Ce₀.₈Sn₀.₂O₂ and Ce₀.₇Sn₀.₃O₂ catalysts display the highest catalytic performance, with T₅₀ = 190 °C and T₉₀ = 210 °C. More importantly, the Ce₀.₈Sn₀.₂O₂ catalyst exhibits superior thermal and catalytic activity stability. It is found that the Ce_1−XSn_XO₂ catalysts form solid solutions, as the X is <0.5. The reduction of Sn⁴⁺ species to Sn²⁺ is significantly promoted by the CeO₂, which is an important factor attributed to the high catalytic activities of the solid solution Ce_1−XSn_XO₂ catalysts. The catalytic activities of the Ce_1−XSn_XO₂ catalysts exhibit a strong correlation to the surface atomic areas of Ce³⁺ and O_α (V_O). In other words, the higher surface atomic areas of Ce³⁺ and O_α (V_O) are, the higher the catalytic activities will have.