Foams Stabilized by In Situ-Modified Nanoparticles and Anionic Surfactants for Enhanced Oil Recovery

Foams have been widely used in oilfields for effective profile control and displacement. However, foams stabilized by surfactants lack long-term stability, especially in an oil reservoir. Here, we have studied the in situ modification of positively charged AlOOH nanoparticles via the adsorption of the anionic surfactant sodium dodecyl sulfate (SDS) and the characterization of foam stabilized by AlOOH nanoparticles in synergy with SDS under different conditions. Changes in the zeta potential and adsorption isotherm of the AlOOH nanoparticles confirmed their modification. The most stable foam was obtained with an SDS/AlOOH concentration ratio of 5:1; further increases of the SDS concentration led to a decrease and subsequent increase in foam stability. The relationships between the zeta potential, three-phase contact angle, nanoparticle aggregate size, and foam stability were comprehensively analyzed, revealing that foam stability Was affected by all of these factors. We concluded that nanoparticles with partial hydrophobicity, a positive or slightly negative charge, and small aggregate size can be adsorbed tightly to foam surfaces and form compact networks in the foam's film, thereby resulting in a stable foam. The SDS/AlOOH-stabilized foam also shows good stability under high temperatures and in the presence of oil. Sandpack flooding experiments showed that the SDS/AlOOH foam can increase and maintain the differential pressure more effectively than the SDS foam. This study provides additional options for using nanoparticles to stabilize foams for enhanced oil recovery.