Study On The Movement Rule And Separation Mechanism Of Oil Drop In Non-Newtonian Fluid Swirl Field

The oil-water swirl separation technology developed at present has the characteristics of small volume,fast separation speed and high separation efficiency,and has satisfied the application demand of oil-water separation in high water-bearing oil field.However,because of the complex composition and easy emulsification,the separation difficulty is increased.How to realize the high efficiency separation has become the most difficult problem which restricts the effective application of oil-water separation and well injection-production technology.For the polymer(polyacrylamide)in the polymer-containing extraction solution,the aqueous solution belongs to the viscoelastic fluid in the non-Newtonian fluid.At present,the mathematical model and prediction model are based on Newtonian fluid,and the influence of viscosity and rheology on the swirl field is neglected,which is obviously not applicable to the study of non-Newtonian fluid.In view of the urgent need of the downhole swirl separation process to be applied in the poly-drive well,it is urgent to study the characteristics of the relevant flow field under non-Newtonian fluid conditions and to guide the design and application of the downhole swirl separation process.In this dissertation,the rheological properties of oil-water mixture under different polymerization conditions were studied,and the viscosity model of non-Newtonian fluid was modified by user-defined method.The spiral guide inner cone cyclone was selected as the experimental object,the numerical-analog analysis was carried out based on the method of computational fluid dynamics,and the flow characteristics of velocity field,pressure field and oil droplet were obtained.Based on particle image velocimetry(Particle Image Velocimetry,PIV),the accuracy of the modified model of non-Newtonian fluid viscosity was verified.On the basis of the computational fluid dynamics method,the flow field variation of continuous and discrete phases in hydrocyclones is analyzed by using Reynolds stress model(RSM),discrete phase model(DPM)and non-Newtonian fluid viscosity modification model.The velocity characteristics,pressure characteristics,separation characteristics and the variation of oil droplet migration trajectory in hydrocyclone were obtained under different conditions.The fitting equation between particle size and separation efficiency was obtained under the condition of polymerization,and the maximum error control could be in the range of 5%.The effects of particle size,flow velocity,concentration,oil volume fraction on the fluid flow characteristics of oil phase concentration distribution,oil droplet size distribution and pressure drop were studied based on the computational fluid dynamics method and the combination of population equilibrium model(Population Balance Modeling,PBM)and oil-water two-phase flow model(Mixture).The characteristics of oil droplet aggregation and breakage and the movement of oil droplet in hydrocyclone under the condition of polymerization were obtained.The flow velocity distribution characteristics and the relationship between pressure loss and parameterization are obtained,and the optimum parameters of groove depth,angle of rise and taper are obtained.Based on the single variable method,combined with non-Newtonian fluid viscosity modification model and discrete phase model,the effects of flow ratio,treatment capacity,inlet oil concentration and concentration on separation efficiency are obtained.Through indoor and field tests,the operating parameters such as shunt ratio and processing capacity are further modified,and the experimental results are in good agreement with the numerical simulation results.