Numerical Simulation Of Oil Drops Coalescence Concentration Behavior In Gravity Oil-Water Separation

Oil-water separation technology is a key production link in oilfield development and production.Oil-water gravity separation method is one of the most economical oil-water separation methods,and its separation efficiency depends on the interaction between oil droplets.However,in the past,the study of oil-water separation under gravity field has always focused on the macroscopic dynamic behavior of oil droplets in the reactor.The mechanism of interaction between oil droplets and oil droplets is still not fully understood.Therefore,this paper uses the multiphysics coupling software COMSOL to numerically simulate the interaction between double oil droplets under the gravity field,and analyzes the key influencing factors.Based on the phase field method of Cahn-Hilliard equation,the behavioral model of oil droplets floating on gravity field is established.Firstly,the influencing factors of the final velocity and deformation of oil droplets during the floating process of single oil droplets were studied from the microscopic point of view.The results show that the larger the oil droplet size cause the larger the deformation and the final velocity tends to be constant with the increase of the particle size.Moreover the greater the oil-water density difference,the smaller the continuous phase viscosity,the smaller the oil droplet viscosity cause the oil droplets.get greater final speed and separate easier.What's more,the interfacial tension of oil and water has a greater impact on the deformation of the oil droplets.Secondly,in the behavior model of the floating coalescence process on the co-linear double oil droplets,the influence of the oil tail flow on the oil droplets was analyzed from the microscopic point.And the coalescence principle of the double oil droplets was revealed.Many factors affecting the coalescence of double oil droplets were studied.The simulations showed that reducing the initial spacing of double oil droplets,oil droplet viscosity,continuous phase viscosity and oil-water two-phase interfacial tension can reduce oil.drip coalescence time.Increasing particle size and oil-water two-phase density difference can also cause it.Finally,in the behavior model of floating coalescence process on parallel double oil droplets,the coalescence and repelling phenomenon of double oil droplets are studied from the microscopic point of view.When the double oil droplet spacing ratio is S<0.5,the double oil droplets coalesce with the distance.With decreasing the oil droplet viscosity,the continuous phase viscosity,and increasing the density difference of the two phases will promote the coalescence of the oil droplets.When the distance between the double oil droplets increases,the double oil droplets will firstly attract the repulsive motion characteristics.As increasing the particle size and the oil droplet viscosity,the repulsion will more pronounced.And decreasing the continuous phase viscosity and the density difference can also cause it.The more pronounced repulsion will have the farther the lateral distance the double oil droplets are separated when reaching steady state.When the double oil droplet spacing ratio S>5,the double oil droplets no longer interact with each other.In this paper,the numerical simulation method is used to reveal the principle of oil-water separation under gravity field from the process of interaction between micro-dispersed phase double oil droplets,which can provide theoretical basis for the design and working condition setting of oilfield gravity oil-water separator,and guide the efficient development of oilfield.At the same time,it also enriches the research theory of oil-water two-phase flow,and provides reference for a more complicated oil-water two-phase flow system.