Study On The Mesoscopic Scale Of The Oil-water Emulsion Interface Behavior Based On Dissipative Particle Dynamics

Currently in oil field the produced fluid of oil field is faced with high moisture content and serious emulsification degree, increases the burden of storage and speed up the equipment corrosion and damage, so new technology is needed to destroy the stability of crude oil emulsion, reduce the moisture content of crude oil for oil-water separation.We use DPD to study the oil emulsion properties and the aggregation behavior of interface active material at oil/water interface. Establish simulation system model and determine the interaction parameters between the beads,based on the theory of integral Newton equation, through the equation of motion and conservative, random and dissipative force to describe the trajectory of beads, analyze the changes of the interface parameters.Research aggregation behavior of different surfactants at oil/water interface,the influence of the surfactant system interface parameters if change the moisture content,as well as the impact of the interface behavior because of the change of the external factors.The simulation result shows that in single surfactant system, the greater the moisture content, the lower the interfacial tension;Mixed surfactants system is better than that of single surfactant system, mixed system own the better interface activity, the effect of the droplet congregating is more obvious.Increase the concentration of NaCl can decrease the interfacial tension of surfactant systems,with the change of NaCl concentration the influence of anionic surfactant system is bigger, the system interface thickness is big, the interfacial activities of anionic surfactant is better than cationic surfactant system.SDBS system have a better interface effect,it still keep in reducing the interfacial tension on higher temperature,but the temperature effect of PEO-PPO-PEO is smaller.DPD is used to simulate the surfactant/polymer system,observe interface behavior of this system and the structure of polymer chain influence the dehydration rate of the crude oil.The simulation result shows that only if the polymer chain length is enough long, can the droplets coalescence rate is accelerated; with the increase of polymer chain length,the interfacial tension increases first and then stabilized.Before the interface not reached saturated, adding polymer reduce interfacial tension,after adsorption saturation the stability of the interface is damaged, macro separation system lost stability.