Highly Stable Foam Stabilized by Alumina Nanoparticles for EOR: Effects of Sodium Cumenesulfonate and Electrolyte Concentrations

Foam stabilized by particles has been applied in enhanced oil recovery (EOR). However, many difficulties in establishing a foam system with high stability, foamability, and resistance to harsh conditions still exist. In this study, foam stabilized by hydrophobic modified alumina nanoparticles was systematically studied. Sodium cumenesulfonate (SC) was used to modify nanoparticles and generate foam. A competitive effect between nanoparticles and SC was found. Specifically, foam stability increased with SC concentration at lower SC concentration range. Foam with high stability and relatively high foamability was obtained at an SC concentration of 20 mM, and then, foam stability sharply decreased because of the competitive effect. The presence of an electrolyte slowed down the adsorption of SC at the air–water interface by forming an ion pair between the headgroup of SC and the cation, which influences foamability and stability. Meanwhile, the electrolyte also caused detachment of particles from foam due to the decrease of hydrophobicity as a result of the decreased SC adsorption. Despite these effects, the particle-stabilized foam maintained high stability in a wide range of electrolyte concentrations. Sandpack flooding experiments showed that the oil recovery rate increased with SC concentration because of the enhanced foamability and stability, leading to a higher displacement efficiency and water flush resistance.