Flow mechanism of nanoparticle-enhanced autogenous foam: Insights from nuclear magnetic resonance and microfluidic experiments

Enhanced oil recovery (EOR) in low-permeability reservoirs has significant challenges due to reservoir heterogeneity and inefficient sweep. Foam-based profile control offers a promising solution; nevertheless, the long-term stability and effectiveness of conventional foams in reservoir conditions remain a concern, and the underlying mechanisms are not fully understood. This study investigates nanoparticle-enhanced autogenous foam as a novel EOR agent to address these limitations. This study integrates core flooding and sand-pack displacement experiments with nuclear magnetic resonance (NMR) and microfluidic analyses to evaluate foam properties, elucidate foam flow mechanisms, and assess EOR performance. This combined approach enables direct visualization of foam flow behaviors and provides experimental validation for the NMR results. The results demonstrate that nanoparticle-enhanced autogenous foam exhibits excellent static and dynamic properties, maintaining stability even under high-pressure conditions, and achieving plugging rates exceeding 95% in water-saturated cores and sand-packs, effectively diverting flow in fractured media and the water layer. NMR and microfluidic analyses reveal that while the foam tends to destabilize in micropores, it retains its stability in macropores, thereby effectively sealing fractures. This foam improves sweep efficiency by inducing the Jamin effect through bubble deformation within fractures and creating negative pressure in the matrix upon foam breakdown, thereby promoting water imbibition. The injection of the foam results in a 13.67% improvement in sweep efficiency. These findings suggest that nanoparticle-enhanced autogenous foam offers a viable and effective strategy for enhancing oil recovery in low-permeability reservoirs.