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Emulsification flooding can effectively enhance crude oil recovery to solve the problem of petroleum shortage. In this work, a modified Janus Nano Calcium carbonate (JNC-12) with a particle size of 30–150 nm was synthesized, and an in situ emulsification nanofluid (ISEN) was prepared with JNC-12 and alkyl polyglycoside (APG). Scanning electron microscope (SEM) showed that the dispersion of JNC-12 in air or APG solution was better than Nano Calcium carbonate (Nano CaCO3). The emulsification properties, interfacial tension, and expansion modulus of ISEN were studied, and the result showed that with the increase in salinity, the emulsification rate decreased, the water yield rate increased, the interfacial tension first decreased and then increased, and the expansion modulus first increased and then decreased. With the increase in temperature, the emulsification rate, emulsion viscosity, and interfacial tension decreased. With the increased oil–water volume, the water yield rate and the emulsion viscosity increased. With increase in the concentration of JNC-12, the water yield rate, the emulsion viscosity, and the interfacial tension decreased but the expansion modulus increased. The emulsion generated by emulsifying ISEN with crude oil was an O/W emulsion, the crude oil viscosity was 4–10 times that of emulsion, and the average particle size of emulsion was 1.107 μm. The addition of ISEN caused the decrease in interfacial tension of oil–water to 0.01–0.1 mN/m. The wettability alteration experiment found that ISEN could change the lipophilic rock to hydrophilic rock. Finally, the core displacement experiments showed that compared with the first water flooding, the oil recovery of the second water flooding after ISEN flooding enhanced by 17.6%. This research has important guiding significance for in situ emulsified nanofluid flooding to enhance oil recovery.

In order to solve the serious problem of oil shortage, the improvement of the emulsification effect of surfactants using nanoparticles was proposed to enhance oil recovery. In this work, first, an amphiphilic nano-calcium carbonate (ANCC) was synthesized, and the dispersion effect of ANCC in saponin solution was studied. It can be found from results that the dispersion effect of ANCC was the best in 5000 ppm of saponin solution, and the dispersion rate decreased with the increase of salinity. Then, the effect of ANCC on the emulsion property, interface tension, and expansion modulus of saponin solution was studied. It can be found from results that with the increase of ANCC concentration, the emulsion rate between saponin and crude oil increased, the water extraction rate decreased, the emulsion particle size decreased, the interface tension decreased, the expansion modulus increased, and the emulsion stability became better. At the same time, with the increase of temperature, the interface tension decreased, and the expansion modulus increased. With the increase of salinity, the interface tension decreased first and then increased, and the expansion modulus decreased. Finally, the effect of ANCC on the oil recovery of saponin solution flooding was studied by displacement experiments. It can be found from results that when the ANCC concentration was 100, 500, and 1000 ppm, the oil recovery was increased, respectively, by 18.42, 20.97, and 24.59%, indicating that the oil recovery gradually increased with the increase of the concentration of ANCC. This work is of great significance for enhanced oil recovery in surfactant flooding.

With the worldwide decline in conventional oil production, tremendous unconventional resources, such as low-permeability reservoirs, are becoming increasingly important. Cyclic water injection (CWI) as an oil recovery method has attracted increasing attention in the present environment of low oil prices. However, the optimal CWI strategy is difficult to determine for a mature oilfield due to the involvement of multiple wells with multiple operational parameters. Thus, our main focus in this paper is to present a novel and systematic approach to optimize CWI strategies by studying a typical low-permeability, namely, reservoir G21. To this end, a comprehensive method that combines the advantages of streamline simulation and fuzzy comprehensive evaluation (FCE) was proposed to identify water channeling in the reservoir. Second, the reliability of the method was verified using tracer tests. Finally, a new hybrid optimization algorithm, the simulated annealing-genetic algorithm (SAGA), coupled with a reservoir simulator was developed to determine an optimal CWI strategy for the low-permeability reservoir. The results show that the CWI technique is viable as a primary means in the present environment of low oil prices to improve the waterflood performance in low-permeability reservoirs. The oil recovery of the most efficient strategy increases by 6.8% compared to conventional waterflooding. The asymmetric CWI scheme is more efficient than the symmetric CWI scheme for the low-permeability reservoir.