Stabilization mechanism of CO2 foam reinforced by regenerated cellulose

Abstract

CO2 foam was widely applied to enhance sweep efficiency through controlling gas breakthrough and channeling during the process of CO2 flooding. However, the poor stability of conventional foam system under the harsh reservoir conditions restricted the enhanced oil recovery (EOR) performance of CO2 foam. Therefore, the CO2 foam reinforced by anionic-nonionic surfactant SS163 and the regenerated cellulose (RC) was developed; also its stability was compared with other foams (e.g. stabilized with SiO2, Al2O3, HPAM and stabilizer-free foam). The static and dynamic foam stability were evaluated by the modified Ross-Miles method, Warning Blender method, oscillation-shear-oscillation rheology. Furthermore, the foam aging rules were investigated via the multiple light scattering method and double-layer glass model. Upon that, the stabilization mechanism by RC was proposed and elucidated by the viscosity, storage and loss modulus, morphological inspection, SEM images and their correlation with foam stability. The results demonstrated that 1% SS163 + 1% RC CO2 foam has the highest foam stability and regeneration capacity compared with other foams. The dynamic variations in the film thickness and diameter of the foam characterized four stages of RC reinforced CO2 foam. The prolonged liquid drainage was attributed to the following four RC stabilization mechanisms: increased viscosity, the stabilization mechanism of RC aggregates, the liquid film ‘skeleton’ formed by RC, and the liquid storage effect of RC. In this work, we introduce the regenerated cellulose in the application of EOR and present the unique stabilization mechanism of RC on CO2 foam. The interface stabilizing capacity, viscoelasticity, thickened behavior and sustainability of regenerated cellulose highlights the application potential in EOR.