Study On Emulsification Performance Evaluation And Injection Mode Of Polymer/Surfactant Flooding

In the process of polymer/surfactant flooding,emulsification often occurs.After a large number of laboratory studies and field tests,it is found that the presence of emulsification helps to improve the recovery rate to a certain extent.However,the understanding of performance evaluation and oil displacement mechanism of polymer/surfactant system is not systematic and comprehensive.So it is necessary to improve the evaluation of the performance of the polymer/surfactant system,study the law of emulsion seepage,and optimize the injection mode.In this paper,firstly,the emulsion was prepared in a static laboratory experiment,and the effects of such factors as salinity of aqueous solution,oil-water ratio,surfactant and polymer concentration in binary system on the stability of crude oil emulsion were studied.Then,the displacement experiment was carried out to form emulsions under the shear action of porous media and inject them into long cores to simulate the effects of surfactant/polymer system and crude oil at different positions.The flow law of emulsions was studied through pressure changes and microscopic pictures.Finally,the heterogeneous three-plate parallel core model flooding experiment was carried out to change the concentration of polymer and surfactant in the surfactant/polymer system,so as to achieve the effect of changing slug viscosity and concentration and optimize the injection mode of surfactant/polymer flooding.The results show that lower salinity and higher oil-water ratio are beneficial to the stability of crude oil emulsion without changing other conditions.Increasing the surfactant or polymer concentration in a certain concentration range can also make the crude oil emulsion more stable.Both near the well and deep in the formation,the pressure drop of the emulsion is concentrated in the latter half of the reservoir,and the higher the oil saturation is,the greater the seepage resistance is.The water seepage resistance of the W/O emulsion is significantly higher than that O/W emulsion.Under the condition of heterogeneous model,Injecting in a manner that reduces the concentration of the polymer and keeps the concentration of the surfactant constant,the effect of improving the recovery is better.