Study On Mechanisms Of Enhanced Oil Recovery By CO₂ Foam Enhanced By Inorganic Particle Armor

Carbon dioxide（CO₂）has become a focus of the world as a main greenhouse gas leading to global warming.Carbon capture,utilization and storage（CCUS）is considered as an important method of deep carbon reduction.CO₂ flooding has been widely used to enhance oil recovery.However,due to the adverse mobility ratio,the sweep efficiency of CO₂flooding is low.Although foam can effectively improve the viscosity of displacement fluids and enlarge swept volume,the instability of foam restricts its utilization.In this paper,inorganic particles and biological surfactants were used to construct interfacial armor to enhance foam and the stability of armored foam was studied.The dynamic interfacial tension and interfacial dilatational viscoelasticity of CO₂/liquid interface were analyzed.On this basis,the microflow behavior of foam enhanced by particles were studied through microscopic visualization experiments.And the plugging and oil displacement of foam with interfacial armor were explored by oil displacement experiment.The results showed that the half-life time of CO₂ foam drainage was obviously increased with the addition of inorganic particles.At 75℃,the half-life time of CO₂foam was about 12 times that of bare surfactant foam,and the foam comprehensive index increased significantly.In porous media,the coarsening,coalescence and burst of CO₂ foam were slowed down because of inorganic particles.The adsorption of particles on the interface also improved the viscoelasticity of the CO₂/liquid interface,which changed the film from liquid-like to solid-like and improved the rigidity of film.The adsorption of particles on the liquid film made the bubble surface become rough.At high water cut stage,the cluster residual oil could be displaced by a way of segmentation by the foam with inorganic particle armor.The columnar residual oil could be displaced by a way of“plugging-displacing-carrying”.The membranous residual oil could be displaced by a way of extrusion and carry.The residual oil in the dead-end pore could be displaced by virtue of high interfacial viscoelasticity.According to experimental results of sandpack flooding,the recovery of oil increased by～40.85%due to the injection of armored foam at 60°C,which was about twice of the oil recovery obtained using bare surfactant foam.