Nanofluid of amphiphilic carbon nitride nanosheets for enhanced oil recovery

As a novel enhanced oil recovery (EOR) technology, nanofluid flooding has become a research hotspot in recent years. However, the current nanofluid flooding technologies face certain limitations, particularly at low particle concentrations. Compared with the conventional homogeneous spherical nanoparticles, amphiphilic nanosheets exhibit higher interfacial activity and variable shapes, making them more promising for EOR applications. This article prepared a nanofluid based on amphiphilic carbon nitride (ACN) nanosheets and studied its physicochemical properties and EOR potential. The results showed that the ACN nanosheets exhibit an obvious lamellar morphology with a transverse size in the range of several hundred nanometers. Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA) revealed that the ACN nanosheets possess amphiphilic properties due to the presence of uncondensed amino and hydroxyl groups at the edges. Water contact angle measurements confirmed the nanosheets’ water-wet behavior. Notably, this amphiphilicity enables the nanosheets to disperse in various polar solvents, reduce the oil–water interfacial tension, and enhance the oil–water interfacial film strength in saline environments. The Zeta potential (ζ) of the 0.01 % ACN nanofluid was −50.8 mV in a neutral environment, proving that it has high colloidal stability. A static imbibition experiment revealed that the imbibition recovery rate increased by 15.75 % at 0.01 % ACN nanofluid, while a core displacement test showed an EOR of 19.21 %. The ACN nanosheets can form a high-strength elastic climbing film at the oil–water interface, which may play an important role in the EOR mechanism. This study provides a new cost-effective nanofluid system for EOR, demonstrating promising application potential.