A mechanistic investigation on NP-stabilized foam three phase displacement characteristics in low permeable porous media

Abstract

Nanopartical (NP)-stabilized foam has found potential applications in unconventional oil recovery as well as greenhouse gas geological storage practices. In this paper, laboratory works were performed on NP-stabilized Supercritical CO₂ (ScCO₂) foam and N₂ foam three phase displacement processes in 49.5 mm length core samples with permeability around 50 mD. Experimental results show the pressure drop in NP-stabilized N₂ foam flooding process is 4.45 MPa, which is higher than 3.85 MPa in NP-stabilized ScCO₂ foam flow case. The oil recovery rate of 7.1% after NP-stabilized N₂ foam flooding, on the other hand, is lower than 9.1% after the NP-stabilized ScCO₂ foam displacement. To understand the mechanisms behind the laboratory results, numerical simulations were carried out with help of the mechanistic Stochastic Bubble Population Balance (SBPB) model. By taking into account the distinct differences on bubble densities as well as the rheological characteristics between NP-stabilized ScCO₂ foam and N₂ foam, together with the additional resistance factors to the water and oil phases in foam flooding processes, the numerical results reproduce satisfactorily the experimental findings on flooding pressure drops as well as oil recovery rates in both foam systems. At last, the foam three phase displacement characteristics, including the dynamic variation behavior of the three phase fluid saturation, the inlet pressure and the bubble density, were numerically investigated. It is expected this study could help understand the NP-stabilized foam flooding behaviors in low permeability porous media.