Abstract
CO2 flooding effectively enhances oil recovery in low-permeability reservoirs while enabling CO2 geological storage. However, natural fractures and high-permeability channels in such reservoirs are prone to cause CO2 channeling, significantly reducing displacement efficiency. To address this challenge, this study innovatively developed a nanospheres inclusion synergistic enhancement system (ISES) based on cyclodextrin polymer (β-CDAM, host) and acid-resistant hydrophobic polymer nanospheres (PARC, guest). This system achieves shear-responsive intelligent viscosity modulation via a supramolecular self-assembly mechanism. The optimal preparation method for ISES was determined using apparent viscosity as the evaluation criterion. Furthermore, the correlation mechanism between the microstructure and rheological properties of ISES was elucidated using pyrene fluorescence probing, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and rheological analysis. Experimental results demonstrate that under conditions of 85 °C and 1000 mg/l NaCl salinity, the viscosity of ISES reached 24.6 mPa s, representing a 92.24% increase compared to the viscosity of β-CDAM. The cavities of cyclodextrin present on the β-CDAM chain enable inclusion complexation with the surface hydrophobic chains of PARC. This interaction constructs a denser three-dimensional network structure, resulting in a significant increase in system viscosity. The system exhibits low viscosity under high-shear injection rates to improve injectivity. Upon entering the reservoir under low-shear conditions, it achieves in situ viscosity recovery through supramolecular self-assembly, thus effectively plugging gas channeling pathways and enabling deep conformance control. This study provides novel insights for preventing and controlling CO2 channeling, holding significant implications for the successful implementation of CO2 flooding.