Low-carbon and high-efficiency nanosheet-enhanced CO2 huff-n-puff (HnP) for heavy oil recovery

CO₂ huff-n-puff (CO₂-HnP) process is a promising technique for enhanced heavy oil recovery. The huff stage of this process involves the formation of foamy oil flow, characterized by dispersed CO₂ bubbles within heavy oil, which plays a pivotal role in both oil recovery and CO₂ sequestration. Maintaining the stability of foamy oil is crucial for the efficient implementation of CO₂-HnP processes. Herein, ultrathin plate-shaped nanosheets are employed as stabilizers for foamy oil. Carboxyl-alkyl composite Janus nanosheets (SANs) are synthesized using a bottom-up approach. Comprehensive characterizations illustrate that SANs, owing to their amphiphilic and Janus nature, efficiently adsorb at the CO₂-oil interface, thereby modifying interfacial properties and enhancing foamy oil stability even at low concentration (0.005 wt%). The incorporation of SANs extends the duration of foamy oil effect, resulting in a substantial enhancement of oil recovery efficiency from 30.7% to 39.4%, and an increase in CO₂ storage factor from 6.5% to 7.8%, compared to conventional CO₂-HnP processes. Micromodel experiments and molecular dynamics simulations show that SANs strengthen foamy oil stability by increasing interfacial activity and reducing CO₂ diffusion rate. Overall, the multifunctional capabilities of SANs in interfacial modification offer promising prospects for enhanced oil recovery and optimizing CCUS efficiency.