| At present, the daqing oil field enter the mid-late oil, the crude oil produced liquid water content is high, the form of the oil emulsion is mainly for the oil-in-water type crude emulsion. In recent years, the oil displacement of binary compound flooding in EOR, at the same time, the recovery of oil displacement agent will have a great effect on the residual liquid in the oil-water emulsion. The present stage theory of crude oil emulsion are mostly stay in the era of the water-in-oil type crude oil emulsion, and for the oil-in-water type emulsion research rarely reported. This paper focuses on the demulsification mechanism of chemical flooding produced fluid problems, system produced liquid binary compound flooding in daqing oil field is studied under the condition of the residues of surfactant and polymer, the different structure of demulsifier effect on oil emulsion demulsification rule, for the future of the field to provide a theoretical guidance in practical application.The crude oil in daqing area as the research object, the preparation of oil-water emulsion with different flooding system, the dehydration rate, emulsion viscosity, interfacial tension, interfacial strength, water phase after the demulsification of oil droplet number and particle size distribution of the oil displacement agent(petroleum sulfonate-Sa and partially hydrolyzed polyacrylamide-HPAM) content on the stability of emulsion.The experimental results show that: with demulsification temperature 45℃, demulsifier added amount 50 mg/L, 2h in the determination of demulsification dehydration rate, Sa and HPAM alone or combined into the oil-water emulsion on the demulsification have different degrees of influence, in oil displacement agent concentration of 200 mg/L case, dehydration rate is from big to small order: the emulsion was added to the emulsion > join HPAM emulsion > join Sa emulsions > join both the HPAM and Sa composite emulsion. After the composite have bigger influence on the dehydration rate, dehydration rate from 74.38% to 50.80%, this shows that the existence of a strong synergetic effect of polymer and surfactant on the stability of emulsion;With the increase of the content of polyacrylamide、petroleum sulfonate, emulsion viscosity increases, reduce the interfacial tension, increase the intensity of the water film between the oil-water, enhance the emulsion stability; the entry into Sa makes the interfacial tension is reduced significantly, with the increase of concentration of Sa, the interfacial tension decreased from original 10.846 mN/m to 0.863 mN/m; when the concentration of water phase containing HPAM is increased from 100mg/L to 500mg/L, the rupture rate reached 100% the required time extended from 8s to 16 s, therefore, the existence of HPAM on water film strength has a great influence; The emulsion containing polyacrylamide, petroleum sulfonate, the lower water phase after the demulsification was analysed and studied. Sa is a surface active agent, ascension in the process of emulsified oil droplet in the dispersion of water phase, and HPAM certain flocculating effect in water; By using laser particle size analyzer analysis showed that the median particle size of oil droplets with the increase of Sa concentration decreases, when the polymer concentration below 200 mg/L, the median particle size of oil droplets by 92.35μm increased to 97.58μm, polymer concentration increased from 200 mg/L to 500 mg/L, the median particle size of oil droplets from 97.58μm reduced to 60.76μm, oil droplets are difficult to gather, resulting in oil droplet sizes too small. |
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