Preparation and Performance Evaluation of Intelligent Oil Displacement Janus Nanosheets

To enhance the recovery factor in low-permeability reservoirs and address the challenge of nanoparticle adsorption at interfaces, a smart oil displacement Janus nanosheet was synthesized using a template method. The Janus nanosheets possess an amphiphilic structure, with one side being hydrophilic due to carboxyl groups and the other side being hydrophobic due to alkyl groups. Compared to spherical nanoparticles, the sheet-like structure of the nanosheets provides a larger specific surface area and stronger interfacial adsorption capacity. Nanofluids were prepared using a simulated formation water with a salinity of 102,495 mg/L, and their properties were evaluated. The results demonstrated that the nanofluid exhibited excellent dispersion stability at 120 °C and a salinity of 102,495 mg/L. The emulsification index at 120 °C was 53.43%, indicating superior emulsifying performance. The nanofluid reduced the oil-water interfacial tension to 0.0203 mN/m and effectively modified the oil-wet rock surface to a hydrophilic state. Oil recovery experiments were conducted on three core samples with varying permeability. For the core with a permeability of 4.64 mD, the highest recovery rate was achieved, with a total recovery factor of 71.09%. Microscopic oil displacement simulations showed the displacement of residual oil after injecting the nanofluid. These comprehensive properties demonstrate that the Janus nanosheets exhibit higher oil displacement efficiency in low-permeability reservoirs, reflecting their intelligent response to reservoir conditions and their potential for improving recovery rates. A field test was conducted in the Q Oilfield, resulting in an increase of 5579 tons of oil, with a cost-benefit ratio of 1.78, demonstrating significant economic benefits.