| With thedevelopment of Enhanced Oil Recovery (EOR) technology, polymer flooding can improve sweep efficiency, surfactant greatly decreased interfacial tension, alkaline flooding can improve wettability. ASP flooding technology which was mixed or combined use the oil displacing agents, improved oil recovery by complementing each other in function and mechanism.Produced water and the crude oil were generated after dehydration of the produced liquid (a mixture of oil and water from the oil wells). And due to the produced water from this process contains large numbers of residual chemicals(polymer, surfactant and alkali). Thus the water produced from ASP flooding forms a complex and stable O/W emulsion system. Without effective treatments of produced water for re-injection process can cause damage, direct discharge of water will pollute the environment, so it is a serious problem. However, conventional sewage treatment technology can not achieve good effect. Therefore it is necessary to study emulsion stabilization mechanism of ASP flooding produced water to provide a theoretical basis for the treatment technology.So far, the domestic and foreign scholars mainly studied the effects of oil displacement agents on the stability of produced water. However, mining and drilling took clay particles into the produced water during the actual process of oil extraction. The emulsion stability affected by interactions between the clay particles and the displacing agents. In this study, In this work, Na-montmorillonite, as a representative of the natural clay, was used to investigate the stabilization effects by measuring oil content in the formulated a series of simulations produced water, respectively, and Na-Mt study polymer particles, surfactants and Na-Mt particles, alkali and Na-Mt particles in ASP flooding impact on the stability of water. And further studied the stabilization mechanism by measuring the zeta potential of the oil droplets, oil-water interfacial tension and the viscoelastic modulus. Microscope was used to observe the state of aggregation of particles and droplets intuitively and so on. (1) With the increase of HPAM concentration, the zeta potential of oil droplets and oil-water interfacial tension decreased, dilational viscoelasticity increased, oil concentration in produced water increased, emulsion stability enhanced. WPS could adsorb at oil-water interface, increasing the interfacial dilational viscoelasticity, reducing the interfacial tension and zeta potential, so greatly enhanced the stability of produced water. The reaction of NaOH and crude polar substances generated active materials, which reduced the interfacial tension. When NaOH concentration was low(<400mg/L), with the increase of NaOH concentration, zeta potential decreased, the dilational viscoelasticity decreased, zeta potential and interfacial tension played a major role in enhancing the emulsion stability. When NaOH concentration>400mg/L, zeta potential increased, dilational viscoelasticity decreased, emulsion stability of the produced water decreased, which did favor to produced water treatment.(2) In ASP flooding produced water containing Na-montmorillonite particles, When oil displacement agents were NaOH0-600mg/L, HPAM0-700mg/L and WPS0-600mg/L, as Na-montmorillonite concentration increased, zeta potential and interfacial tension decreased, dilational viscoelasticity increased, thus enhanced the stability of produced water, when the concentration of Na-montmorillonite was100mg/L, emulsion stability was the strongest. With further increase of Na-montmorillonite particles concentration, interfacial tension increased, the dilational viscoelasticity decreased, which contribute to water treatment; especially when a large concentration of NaOH, Na-montmorillonite particles increased zeta potential and the interfacial tension, and decreased dilational viscoelasticity, which do great damage in the stability of the produced water. |
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