Study On Foam Stabilization And Flow Characteristics By Nanoparticles For Heavy Oil Thermal Recovery

Foam is a commonly used plugging agent for oil and water wells,which can adjust the injection-production profile and improve oil recovery through various mechanisms such as the Jiamin Effect.With the development of heavy oil resources,foam fluids are also widely used to control steam overriding,steam channeling and hot water fingering,increasing the sweep area of steam and hot water.However,foam is still a thermodynamically unstable system.How to improve the temperature resistance of foam has always been a problem,and whether the SiO₂nanoparticles with strong temperature resistance could further enhance the high temperature stability of the foam has attracted the attention of experts and scholars all over the world.Firstly,foam static performance evaluation experiment was conducted to optimize the SiO₂ nanoparticles with HY-4 foaming agent system,and the synergistic mechanism of nanoparticles with surfactant was also discussed.Secondly,the temperature resistance of the foam system,the apparent viscosity at different temperatures of the foam were evaluated and the microscopic morphology at different temperatures of the foam was observed.Then the high-temperature flow characteristics of the foam were studied by using the two-dimensional micro-etching model and sandpack models.Finally,the CMG reservoir numerical simulation software was used to fit the results of foam core flooding experiments,and the effects of different foams on heavy oil thermal recovery were discussed.The results show that the hydrophobically modified SiO₂ nanoparticles can greatly increase the foam stability with HY-4 benzenesulfonate foaming agent,and the foam system consisted of 0.5 wt%HY-4 foaming agent and 1.0 wt%hydrophobic SiO₂ nanoparticles has the best comprehensive performance.Nanoparticles adsorbed with an appropriate number of surfactant molecules can be firmly adsorbed on the gas-liquid interface,which made the half-life time of HY-4 foam extended by more than 3 times.Nanoparticles can significantly improve the temperature resistance of foam systems,and the apparent viscosity of the reinforced foam is about twice larger than that of the normal foam within 100°C.The half-life of the reinforced foam after aging at 150°C for 12 h is 1.3 times longer than that of the normal foam.Due to the protection of surface particles,the reinforced foam wrapped with a dense nanoparticle adsorption layer has stronger plugging and oil displacement abilities than the normal foam in the process of high temperature core flooding.Moreover,the reinforced foam produced by150°C core flooding experiment has smaller particle size,higher sphericity and stronger extrusion resistance than that of the normal foam.The numerical model fits the results of foam flooding experiments well.The simulation results show that the reinforced foam has strong high-temperature stability and it can resist hot water or steam flooding to some degree.The reinforced foam play a more permanent role in controling steam overriding and channeling,which can increase the oil recovery from the bottom of the reservoir.