Study On The Motion Law Of Oil Droplets In Chemical Flooding Produced Water Under Different Field

With the development of tertiary oil recovery,chemical flooding is more and more popular to the production of old oil fields with high water cut.Coupled with the complex role of flooding agents,the treatment of chemical flooding produced water has become a scientific problem demanding prompt solution.In this paper,based on the produced water treatment process of "double swirling + sedimentation + filtration",the oil-water separation characteristics of produced water and the numerical simulation of the swirling and sedimentation process are tested to get the oil droplet movement law in produced water,which provides a theoretical basis for the optimization of the process.First,produced water physical parameters and the characteristics of settlement separation under the role of flooding agents were studied experimentally,the research results reveal the influence mechanism of flooding agents on the floating of oil droplets in produced water.At the same time,the method of measuring interface parameters is provided for the follow-up simulation.In terms of theory,the equation of motion of oil droplets under different field is derived.And the theoretical model of oil droplet coalescence time under gravity field is optimized by combining the relative motion of oil droplets,liquid film drainage and liquid bridge expansion,by which the coalescence process of oil droplets in gravity field is described more completely.Based on the combined process of “double swirling + sedimentation + filtration”,a threedimensional hydrocyclone model is established.The floating and coalescence law of oil droplets in the hydrocyclone is studied by the population balance method.Oil droplet coalescence is characterized by the average size of oil droplets,and the floating of oil droplet is characterized by oil content and oil-water separation efficiency.The result shows that the oil content in the central swirl area gradually increases with the increase of oil droplet particle size,and the separation efficiency increases first and then decreases with the increase of inlet flow.The order of oil volume fraction of the four parts is: Cylindrical Section > Large Cone Section >Small Cone Section > Parallel Tail Section.In addition,as the viscosity and oil phase density increase,the cyclone separation efficiency gradually decreases.The split ratio and hydrocyclone type also have a significant effect on the separation efficiency of the hydrocyclone.The structural parameters of the cyclone were optimized,and the oil phase outlet diameter was 9 mm and the length of the cylindrical section was 75 mm.Based on the sedimentation process in the process,in this paper,A simple model of oil droplet motion in gravity field is established to study the laws of the floating and coalescence of two oil droplets in the produced water.The result shows that during the oil droplet floating process,the increase of polymer concentration and surfactant concentration will reduce the oil droplet floating speed;during the process of oil droplet aggregation,the oil droplets of different particle sizes and the coalescence time of the oil layer are different,the smaller the oil droplet particle size,the shorter the coalescence time;the liquid bridge will appear in the droplet coalescence process.In the process of II(b)type coalescence,the bigger the ratio of droplet size is,the shorter the coalescence time is.In the process of I type coalescence,with the increase of the droplet size,coalescence time becomes longer.In addition,the coalescence time of oil droplets first increase and then decrease with the increase of low concentration of Surfactant,and increased with the increase of high concentration of Surfactant and polymer concentration.In addition,the coalescence time increases with the increase of Oh number.