Abstract:

Since the influences of pressure on the performance and seepage characteristics of CO₂ foam are unclear, in this work, the effects of pressure on the foaming capability, stability, bubble diameter, plugging capacity, and oil displacement efficiency of CO₂ foam were systematically investigated through experimental methods. The results showed that, the higher the pressure, the higher the foaming capacity of the CO₂ foam system, however in contrast, there was a competitive mechanism in the effect of pressure on foam stability. The nano-SiO₂-reinforced foam system effectively addressed the problem of instability in traditional foams. Negative correlation was observed between pressure and bubble diameter, with high-pressure conditions producing smaller and more uniform bubbles. Elevated pressure could promote the formation of CO₂ foam with good uniformity and stable migration in cores. Moreover, the increased pressure could enhance the effective viscosity and plugging efficiency of CO₂ foam, expanding its applicability to reservoirs with diverse ranges of permeability. High-pressure conditions could improve the oil displacement efficiency of CO₂ foam flooding, alleviating the disadvantages situation caused by reservoir heterogeneity and achieving substantial oil recovery enhancement. This research might deepen the understanding of the role of pressure in CO₂ foam-enhanced oil recovery and provide theoretical basis for effective gas channeling control strategies.

Key words: nano-SiO₂, stability, CO₂ foam, gas channeling, enhanced oil recovery