Polymers vs. Foams and Emulsions: Distinct Viscoelastic Contributions to Oil Displacement

Abstract This study investigates the role of viscoelasticity in oil displacement by comparing polymer-based and cellulose nanocrystal (CNC)- stabilized foams and emulsions in enhanced oil recovery (EOR). While all exhibit viscoelastic behavior, their influence on oil mobilization differs due to the nature of their internal elasticity. The research examines the stability, rheological properties, and interfacial characteristics of CNC-stabilized foams, focusing on their ability to modify wettability, reduce interfacial tension (IFT), and enhance pore-scale oil displacement. By optimizing CNC formulations, this study aims to develop a stable and sustainable alternative to conventional surfactant-based EOR fluids, utilizing tailored viscoelastic properties to improve recovery efficiency. Capillary tube flow experiments under a microscope are used to visualize how CNC-stabilized foams displace residual oil. Microscopic analysis quantifies bubble size, coalescence, and structural stability over time. Rheological properties, shear and complex viscosity, storage (G′) and loss (G″) moduli, are measured to assess flow behavior and deformation resistance. Interfacial properties, including contact angle and interfacial tension, are examined to evaluate wettability alteration and oil detachment. These measurements establish the role of CNC-stabilized foams in enhanced oil recovery. We hypothesize that, unlike polymers which primarily increase viscosity to promote uniform displacement, CNC systems enhance pore-scale mobilization by enabling droplet deformation and dynamically adapting interfacial properties, effects that are particularly beneficial in heterogeneous media. Rheology confirms shear-thinning behavior across all formulations. This study demonstrates that CNC-stabilized foams mobilize oil through viscoelastic effects arising from the dispersed gas phase. By tuning CNC–CTAB concentrations, their rheological properties and stability can be controlled, improving pore-scale performance in heterogeneous reservoirs