Investigation of synergism between surface-grafted nano-cellulose and surfactants in stabilized foam injection process

- A functionalized nano-suspension was suggested to stabilize the foam film.
- The nano-suspension synergized with surfactant to reverse the surface wetting.
- The embedment of the nano-suspension rendered the film superior viscoelasticity.
- The EOR mechanisms of foam flooding were visually observed through the micromodel.
- The nano-suspension stabilized foam led to more significant reduction of oil saturation.

The enhanced oil recovery (EOR) efficiency of a foam injection is largely dependent on the stability of foam film especially when crude oil is present. In this study, a surface-grafted nano-cellulose (sgNC) was used to stabilize the film of a surfactant foam and then employed in foam EOR process. The synergism between sgNC and the surfactant was first investigated in bulk through direct measurements of oil/water/solid interfacial behaviors, foam morphology, foam decay, interfacial dilational rheology, etc. Particular emphasis was placed on the microflow behaviors of the sgNC stabilized foam in porous media with crude oil to understand the EOR mechanisms behind. The results showed that the incorporation of sgNC in the surfactant solution further reduced the oil/water IFTs, and enhanced the emulsifiability and wettability alteration of the surfactant because of its amphiphilicity. The presence of sgNC in the surfactant foam film significantly increased the film thickness and obstructed liquid drainage. The resultant foam film was fairly viscoelastic, as revealed by the rheological analysis. The oil displacement dynamics observed in the visual microflow model indicated that the viscoelasticity of the foam film rendered the gas bubbles superior stability during migrating in porous media, thus leading to a favorable mobility control and significant reduction in the residual oil saturation. Emulsification, Jamin effect and squeezing accounted for the EOR of foam injection at pore scale.