Keys to improve the efficiency of nanoparticle-stabilized foam injection based on influential mechanisms

The effect of the existence of nanoparticles on foam stability, foamability, and the oil recovery factor (RF) has been studied experimentally, and influential phenomena and mechanisms have been examined. A sequence of experiments, including, ‘foam bulk-static experiments’, ‘surface tension (ST) measurements,’ and ‘micromodel foam flood,’ were designed and then implemented to study the foam behaviour in two foam systems: (1) anionic-nanoparticles + cationic-surfactant and (2) anionic-nanoparticles + anionic-surfactant. This study provides a comprehensive insight into the mechanisms affecting the stability of nanoparticle-stabilized foam. Also, despite previous studies, the effect of Marangoni flow on nanoparticle-stabilized foam has been discussed briefly. Results show that the interactions of effective mechanisms work differently in the two series. In the like-charge system, surfactant molecules accumulate in the interface of lamellas due to repulsive forces; therefore, stability and foamability improve as surface tension and molecular diffusion reduce. Additionally, Marangoni flow restitutes the negative impact of gravity drainage. In the unlike-charge system, observations illustrate that nanoparticles reach the interface. The presence of nanoparticles at the interface increases detachment energy significantly, and as a result, the stability is boosted. The accumulation of nanoparticles in the interface changes it to a solid-like surface with limited diffusibility and viscosity. Although Marangoni flow is lost, reducing molecular diffusion improves foam stability. Flooding tests show that foam stability increment improves sweep efficiency at near-wellbore areas even when foamability is weak. Finally, it can be claimed that in the unlike-charge system, the sweep efficiency and foam stability increase to a greater extent.