Improved foam stability through the combination of silica nanoparticle and thixotropic polymer: An experimental study

Foam flooding serves as one of widely-used enhanced oil recovery (EOR) techniques for developing oil and gas resources. However, the foam is a thermodynamically unstable system, limiting its EOR performance. Hence, this study aims to provide a novel strategy to stabilize foam through the combination of nanoparticle and thixotropic polymer and tries to reveal the foam-stabilizing mechanism. Firstly, a novel water-soluble thixotropic polymer (WTP) was developed, which is able to thicken solution under low shear rates and become thin under high shear rates. Such thixotropic behavior helps to stabilize foams and has little effects on the stir-foaming process. Then the hydrophobic nano-SiO2 particles was modified by sodium dodecyl benzene sulfonate (SDBS) with the assistance of ultrasonic treatment. Coupled modified nano-SiO2 and WTP, this study develops a novel foam system with a high foaming volume and a long half-life time. This foam system is suitable for the high-temperature and high-salinity reservoir condition and can effectively enhance the oil recovery through foam flooding. The microscopic observations show that the foam system consists of fine, round and uniform bubbles, which may slow down the film drainage and restrain the gas diffusion. At the same time, the modified nano-SiO2 particles generate a "solid shell" on the bubble surface and improve the elasticity of foam film; the WTP forms molecular spatial networks in solution and mitigates the nanoparticle agglomeration. As a result, the synergistic effects of nano-SiO2 and WTP can improve the stability of foam significantly. (C) 2021 Elsevier B.V. All rights reserved.