| With more and more crude oil exploited, the resource of crude oil is becoming less and less. In order to enhance oil recovery, more and more oil fields began to use ASP(alkali,surfactant and polymer)flooding oil recovery techniques. Besides, there are abundant heavy and super heavy oil resources in china. These oils contain large amounts of asphaltenes and other natural active ingredients, which have interactions with oil-displacing agent, especially the interaction asphaltene and oil displacement. The interfacial film is formed on the surface of the oil droplets because of these interactions, which increases the difficulty of produced water oil-water separation. In order to have a better industrial treatment of oilfield produced water for meeting the standards of re-injection or emissions and reduce environmental pollution, we need to have a depth study of the stability mechanisms of ASP flooding water emulsion. Therefore, the study of the mechanism of the interaction between asphaltene and oil displacement has a great significance for the industrial treatment of oilfield produced water.In order to individually discuss the mechanism of oil displacement agent for ASP flooding produced water emulsion stability, the light oil was used as model oil, which could exclude the complex natural active ingredients in crude oil. On this basis, the interaction mechanisms between asphaltene and oil-displacing agent on the oil-water interface and the influences for the emulsion stability of simulated ASP flooding produced water were studied. The interfacial tension, dynamic interfacial tension, Zeta potential of oil droplets and the rheology of oil-water interface were investigated by spinning drop inferface tensiometer, Zeta potential analyzer and surface rheology analyzer. The results of the study were as follows.(1) The light oil used in the study didn’t contain asphaltenes, naphthenic acids and other acidic components in crude oil. So, The alkali had little effect on the stability of simulated produced water. Petroleum sulfonate (WPS) as a kind of surfactant could well reduce the interfacial tension between oil and water, so that the stability simulated produced water increased. Partially hydrolyzed polyacrylamide (HPAM) had little effect on interfacial tension, but enhanced the viscosity of the bulk, and reduced the rate of oil-water separation, which had little effect on the final stability of simulated produced water. Salinity could enhanced ability of surfactant to reduce the interfacial tension. The oil concentration increased clearly and the stability of simulated produced water was enhanced significantly.(2)The alkali could react with some acidic functional groups of asphaltene molecules and enhanced the hydrophilicity of asphaltene molecules. The reaction could reduce a large degree of interfacial tension and asphaltene molecules also had a faster diffusion rate to the interfacial film. In the decay of dynamic interfacial tension, fast decay played a major role. Space reticular structure formed on the oil-water interface was more dense, and its interfacial viscoelasticity was significantly higher than other situations. There were competitive adsorptions between surfactant and asphaltene molecules on the oil-water interface. Both reversible adsorption and desorption process extended the adsorption process on the oil-water interface. Slow decay played a major role in the decay of dynamic interfacial tension. HPAM had a large molecular size and a higher molecular weight, which affected the activity of HPAM and diffusion to the interface. The alkyl chains provided steric hindrance and prevented the dissolved asphaltenes to gather. Slow decay played a major role in the decay of dynamic interfacial tension. Asphaltenes and ASP flooding oil-displacing agent adsorbed on the oil-water interface and interacted with each other, which made the interface of drops adsorbed more negative charge and negative potential enhanced. |
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