Synthesis of water-soluble and stable carbon quantum dot nanofluid mediated by <i>Scenedesmus</i> extract for enhanced crude oil recovery

Under the background of ecological civilization construction in the new era of “carbon neutrality and carbon peaking,” there is an urgent need to develop more efficient and environmentally friendly methods to address the challenges posed by traditional enhanced crude oil recovery (EOR) technologies. Scenedesmus was cultured in the laboratory, with its main components—pigments, proteins, and lipids—utilized as modifiers and dispersants for carbon quantum dots (C-Dots). The resulting bio-nanofluid exhibits excellent water solubility and stability, with a particle size of less than 10 nm. The EOR mechanisms of the bio-nanofluid are as follows: Altering wettability and reducing the adsorption capacity of oil and water on the surface of quartz sheets. Inhibiting asphaltene deposition through adsorption and dispersion. Demonstrating a remarkable macroscale oil-washing effect, achieving an efficiency of 99.47%, coupled with self-cleaning properties. At the microscale, the bio-nanofluid penetrates oil droplets, breaking them into numerous fine oil particles. Core displacement experiments further validate the bio-nanofluid's efficacy, showing significant oil displacement capability. At an optimal concentration of 500 ppm, the EOR performance in low-permeability cores reaches 18.37%. The integration of bio-nanotechnology into oilfield applications, while balancing “economic benefits” with “sustainable development” objectives, presents a promising avenue for future development.