The technology for EOR with CO2, well established for over 50 years, is now being used to mitigate carbon emissions through their capture and storage in deep geologic formations. Mobility control in CO2 flooding is critical for improving CO2 sweep efficiency and optimization of CO2 storage capacity. The potential weaknesses of surfactant-stabilized CO2 foam, such as lack of long-term stability and adsorption loss, increase the operation cost significantly. The results presented in this paper will provide an alternative for CO2 mobility control, in which the weakness caused by using surfactant, we believe, can be avoided.

In this paper, we present a process for generating nanoparticle-stabilized CO2 foam, in which nanoparticles, instead of surfactant, were used to generate and stabilize CO2 foam in a static solution. The paper also describes the effects of different factors such as particle concentration, brine salinity, pressure, temperature, and surfactant, on CO2 foam generation. The results of this research demonstrated that supercritical CO2 foam was successfully generated in a static sapphire tube with the aid of nanoparticles. Particle size was determined to be in the range of 100-150 nm. The experimental results revealed that stable CO2 foam was generated in a 0.5% nanosilica dispersion at 1500 psi and 25°C. The height of the foam in the observation cell was used to characterize CO2 foam stability. It was also observed that, as the nanosilica concentration was lower than 0.3% or higher than 1.0%, only a little CO2 foam was generated. Temperature and brine salinity were observed to have similar effects on CO2 foam generation. As the temperature and brine salinity increased, less CO2 foam was observed. On the contrary, pressure had a different effect on CO2 foam generation. When the pressure was increased from 1200 psi to 2000 psi, more CO2 foam was generated in the observation cell. With a small amount of surfactant adding to nanosilica dispersion can improve CO2 foam generation.

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