Foam enhanced oil recovery (EOR) techniques commonly use N2 and CO2 gases. Previous studies have compared the foam generated by these two gases, and it has been found that CO2 becomes weaker and less stable at its supercritical conditions, reducing its effectiveness in creating stable foam. In contrast, N2 forms stronger foam at these conditions. Limited research has investigated the use of a CO2/N2 mixture foam in bulk media. It was found that adding N2 to CO2 has shown potential in producing more stable foam in oil-free porous media. This article reviews the advantages and disadvantages of CO2 foam and potential methods of improving its use in oil production. In addition, the performance of mixed CO2/N2 foam in crude oil-saturated sandstone cores was studied and compared to pure CO2 foam, with optimization of total injection rate, CO2/N2 ratio, and foam quality to achieve maximum oil recovery and stable foam. Results showed that the mixed foam gave a higher recovery than the CO2 foam. The addition of N2 to CO2 improved foam stability and enhanced oil recovery up to a 20 % by volume N2, but beyond this range, oil recovery was adversely affected. Increasing foam quality up to 80% produced a finer-textured foam, improving stability and recovery, but beyond 90%, the foam becomes coarser and less stable, likely due to the formation of dry foam. Increasing the injection rate affected stability of foam and recovery of oil, as higher rates of injection produced high shearing rates that may cause collapse of foam. The study suggested useful outcomes for addressing supercritical CO2 foam instability in sandstone reservoirs and advancing understanding in the developing area of foam behavior research.

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