Effects of Nano-Particles on Foamy Oil of CO2-Heavy Oil System under Nonequilibrium Conditions

In situ formation of foamy oil has been widely utilized to improve the heavy oil recovery, especially considering its cost efficiency. Therefore, the stability and strength of generated foam actually play a crucial role on the foamy oil recovery. In this work, the effects of nanoparticles (NPs), the additives in a CO2-heavy oil system, on the so-called NPs-stabilized foam of CO2-heavy oil systems are experimentally and mathematically assessed. Specifically, a visual high temperature high pressure (HTHP) foam generator is utilized to investigate the foam stability of NPs- CO2-heavy oil system. The effects of different NPs concentrations and NPs types on the foam stability is systematically observed and analyzed with measuring the relationship between the height of foam column and time under nonequilibrium conditions. Then, a mathematical model is proposed to quantify processes of NPs-stabilized foam generation and collapse according to the experimental results. The results show that NPs of SiO2 with a size of 20-30 nm can effectively improve the foam stability and generation of CO2-heavy oil system compared with pure CO2-heavy oil foam. The concentration of NPs impose impact on the foam properties to some degree. Also, different types of NPs, SiO2, Al2O3 and MgO, on the foam stability are experimentally probed mainly to unveil the difference between metallic NPs and non-metallic NPs. Finally, the exponential functions with parameters characterizing concentration and nonequilibrium conditions are developed to quantify the foam generation and stability under nonequilibrium conditions.