| The distribution of oil and water in the produced fluid of ASP flooding is complex.Under the synergistic effect of shear stirring of porous media in the formation and surfactant,emulsion is easily generated in the produced fluid,causing great damage to its transportation pipeline equipment,increasing the burden of storage and transportation process,and it is necessary to destroy the stable state of the emulsion in the produced fluid to achieve the purpose of oil water separation.Oil droplet coalescence is an important step in crude oil demulsification,so it is necessary to study the process analysis and coalescence mechanism of oil droplet coalescence.Based on the research of relevant literature,this paper analyzes the influencing factors of oil droplet coalescence in produced liquid under the ASP flooding method and the force characteristics of oil droplets in the water phase,establishes an oil droplet coalescence model,and studies the influencing factors of oil droplet coalescence based on the finite element simulation method,The microscopic interaction between oil droplets during oil droplet coalescence was studied,and the effects of crude oil components and surfactants on oil droplet coalescence were analyzed.The research results showed that:(1)During the coalescence process,the velocity of the two oil droplets at the two oil films is significantly higher than that at other locations,and there are severe fluctuations,resulting in a trend of relative motion.As the distance between the droplets gradually decreases,the increase in fluid flow rate gradually decreases.Finally,the coalescence is completed at the location of the maximum flow rate.After coalescence,the flow rate in the system gradually decreases,and finally reaches stability.(2)When the size of two oil droplets is the same,the two oil droplets converge at the intermediate position to form new oil droplets.When the size of the two oil droplets is different,the large oil droplets attract the small oil droplets to move towards the phase,and there is no obvious corresponding relationship between different oil droplet sizes and the coalescence time.When the droplet spacing is 0.8 mm,the two droplets do not coalesce due to the excessive spacing.(3)There is no significant change in the coalescence time of oil droplets under different oil droplet numbers,and when the size of one of the oil droplets changes,the coalescence process of the oil droplets will also change significantly.As the size of one of the three oil droplets gradually increases,the time for the completion of oil droplet coalescence gradually decreases.When the size of the oil droplets reaches the nanoscale,the time for the completion of oil droplet coalescence can reach 4 hours.(4)After adding surfactants,the stability of the emulsion increases significantly,and with the gradual increase in pump flow,the stability of the emulsion system also gradually increases.However,there is no cross or sharp increase in the oil content change curves of different surfactants.(5)The molecular dynamics simulation results show that during the coalescence process between oil droplets,the oil film will pull,the oil film at the middle position will move in opposite directions,and the oil film at the upper and lower sides will migrate outward.Moreover,under the same number of carbon atoms,the more complex the molecular structure of the carbon chain,the larger the water molecular space occupied between the oil films,which means the more complex the molecular structure of the crude oil in the emulsion system,The greater the strength of the oil film between the oil droplets,the greater the emulsion liquid system.Overall,the stability of crude oil molecules is as follows: saturated hydrocarbons>carbon carbon double bonds>carbon carbon triple bonds>cycloalkanes.This article has important significance for improving the efficiency of crude oil water separation and reducing the burden of crude oil storage and transportation. |
