Study On The Interface Mechanism Of Oil-water Emulsion Based On Dissipative Particle Dynamics

The technology of ASP flooding oil in the form of oil-water emulsion,emulsion oildroplet radius is getting smaller and smaller and the emulsification degree is more and moreserious.Study on the mechanism of emulsion interface,analysis of various factors,such as thetype of surfactant,the surfactant concentration,salinity,etc., influence on oil-water emulsionsystem structure,providing the theoretical basis for improving the efficiency of oil-waterseparation.Dissipative particle dynamic (DPD)is a method of coarse-grained,on mesoscale,tosimulate complex fluid dynamics behavior.In this paper,using dissipative particledynamics,studied the effects of surfactant and polymer on the interface of oil-watersystem.Establish oil/water/surfactant ternary model and set the interaction parametersbetween beads,making the free movement of bead speed and position in accordance withNewton’s equations of motion.The three kinds of interaction force between beads byconservative,dissipation,and random forces,as well as the equation of motion trajectory ofbeads is described,drawing the trend on the properties of interface parameters.The simulationresults are compared with the experimental values,the simulation calculation results with theexperimental and theoretical results are identical with each other.Study analyzed the effects ofdifferent types of surfactants and their concentration and salinity change in the behavior ofthe oil-water interface system.Under different moisture content,oil-water emulsion is differenttype.The surface active agents and the different structure of surfactant influence the interfaceparameters.The results showed that surfactants on oil-water interfacial layer to clusterform,ionic surfactant reduces the interfacial tension of high efficiency,which in lowconcentrations can reach saturation,but interfacial adsorption tendency.And non-ionicsurfactants reduced the efficiency of the interfacial tension is low,but the trend of stronginterface enrichment.Surface active agents method is combined with the advantages of twokinds of surfactants,can enhance the interfacial activity and can make the interfacial tensionreached lower level.At low and high moisture content,oil-water emulsion form theoil-in-water-in-oil and water-in-oil-in-water type of double emulsion,with the increase ofmoisture content,the trend of interfacial tension is increased before it is reduced.Comparedwith the single head or the tail surfactants,double tail or double head type surfactants reducesthe efficiency of the interfacial tension obviously. Using DPD simulate the copolymer as emulsifier influence on the morphological ofoil-water emulsion,and polymer effect on the interface of surfactant/oil/water.The resultsprove that droplet coalescence process,the system pressure to reduce gradually,after reachinga certain value remains unchanged,indicating that the form of emulsion is dynamicbalance.Compared with a single system,the surfactant/polymer composite system have astrong ability for reducing the oil-water interfacial tension,and the system to add more thepolymer concentration,the greater the interfacial tension reduction.