Computational Study On Multiphase Displacement Characteristics Of Nanoparticle Stabilized Foam And Surfactant Foam Fluid In Porous Media

Foam displacement technology can alleviate the problems of gravity overpressure and viscous finger during gas flooding,and plays an important role in EOR.With the continuous development of foam technology,nanoparticle stabilized foam displacement technology has gradually come into public view and become a new favorite of researchers.The Stochastic Bubble Population balance model(SBP)has been widely used in the study of foam flow characteristics in porous media,but the field of foam behavior stabilized by nanoparticles is still new to SBP model,which is worthy of further exploration.In this paper,SBP model was used for the first time to analyze and study the process of nanoparticle stabilized foam displacement,and during this process,the empirical parameters of the model--foam formation rate K_g and maximum foam density n_max were calibrated.In addition,the fluid flow characteristics in the process of surfactant stabilized foam flooding were studied.A more accurate relative permeability formula was adopted,and the influence of capillary pressure was considered to further improve the governing equation,so as to explore the application prospect of the model in enhanced oil recovery by foam flooding.The parameters of SBP model were calibrated during the numerical simulation of two-phase fluid flow in nanoparticle stabilized foam flooding.The results show that the foam generation rate K_g has little effect on the displacement process,while the maximum foam density n_max increases from 100 mm^-3 to 8000 mm^-3 with the addition of nanoparticles and the increase of the concentration.In addition,when the concentration of nanoparticles is less than 1.5wt%,the higher the concentration,the greater value of n_max,the greater change of pressure drop along the core,and the better displacement effect.However,when the concentration was greater than 1.5wt%,the changes of pressure drop and n_max were no longer obvious.SBP model after improved was used to simulate the oil/gas/water three-phase fluid displacement process.The results show that the pressure change along the displacement is 0.97MPa,the oil displacement rate is 36%,and the water displacement rate is 64%.The simulation results are close to the experimental results,indicating that the improved SBP model has stronger applicability in the foam displacement process.In addition,the influence of parameters n_max,K_g and oil phase viscosity in the reservoir on the displacement effect was explored.The results show that the larger the n_max,the richer the foam,the greater the change of oil and water saturation,and the better the displacement effect.The value of K_g only works at the inlet and has no significant effect on final saturation or recovery.The higher the oil viscosity is,the higher the relative permeability of water is and the lower the relative permeability of oil is,resulting in the lower oil recovery rate.Finally,the value of foam density-n_max was compared between surfactant stabilized foam and nanoparticle stabilized foam,and the results showed that the value of n_max by nanoparticle stabilized foam was much higher than that of surfactant stabilized foam,which reflected the greater contribution of nanoparticle to the stability of foam.