| The viscous crude recovery is important in the petroleum industry because the resources of viscous crude are plentiful in China. Although the steam flooding is the most popular process used in the viscous crude recovery nowadays, it will consume much energy to produce high temperature steam, and it is hard to be used to drive the ultra-viscous crude whose viscosity is higher than 50000niP.s. In recent years, many kinds of viscosity-reducing agents have been applied in the viscous crude recovery. The viscosity of viscous crude will be dramatically decreased with the transformation from water-in-oil to oil-in-water emulsion. However, there are two problems in the development of viscosity-reducing agents, and they will block the application of chemical agents in steam flooding and other viscous crude recovery techniques.The first problem is that the viscosity-reducing agents should meet the demands of hi~h thermal stability, strong salt tolerance and lower cost simultaneously because of the recovery depth of steam flooding gettinc deeper and the geometric condition becoming more complicated. However. the commercial available ~~iscosit~-reducing agents now can not meet the demands mentioned above. The other problem is that almost all of the viscosity-reducing agents are only to be used in the specified oil, and the reason keeps unclear until now.To solve the problems mentioned above, this thesis focussed on the relationship between composition of crude oil and the structure of viscosi~'-reducing agents. Element composition, hydrocarbon group composition of model viscous oil used in the emulsion were also determined. Then the relationship between viscous-reducing agent's structure and its performance were discussed. Some new conceptions were put forward to describe the emulsification process of viscous crude.The stability, interfacial tension and oil droplet diameter of viscous oil emulsion have been determined. It was found that the content and structure of asphaltene, wax and natural carboxylic acid play important roles in emulsification process.In this thesis, it's found that the viscous oil will dissolve more asphaltene if there is more aromatic carbon in it, and thus it is difficult for viscous oil to be emulsified because of the less intensive interface film between oil and water formed by asphaltene. However, when the Aromaticity of asphaltene is high, it will stop the viscosity-reducing agent from entering into the interface between water and oil, and thus the oil can not be emulsified. Wax with long paraffinic chain in the viscous oil is easy to be absorbed on the oil and water interface so that it can form a compact absorption film, therefore, it is also difficult to form oil-in-wateremulsion. It is found that the higher the wax content in viscous oil, the harder the formation of oil-in-water emulsion.Natural carboxylic acid in viscous oil plays an important role in the emulsification of viscous oil. It is found that the viscous oil can be emulsified by alkali solution if more than 1.4 percent natural carboxylic acid was contained in the viscous oil, and the oil containing less natural carboxylic acid can also be emulsified by adding other emulsifier. It is also found that the natural carboxylic acid with higher molecular weight and Aromaticity is easier to form oil-in-water emulsion.The function of natural carboxylic acid in the viscous oil emulsion as described above has been confirmed on three aspects. First the emulsion performance of the viscous oil with different content of natural carboxylic acid was compared. Then the emulsion performance of the viscous oil with and without natural carboxylic acid was compared. And finally the emulsion performance of the viscous oil with original natural carboxvlic acid whose concentration is less than 1.4% or more than 1.4% through the addition of additional natural carboxylic acid was compared.Synthetic carboxylate type emulsifier that is similar to natural emulsifier is suitable to viscous oil with lower acid value because these additio...
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