With the contradiction between an increase in global energy consumption and a decline in conventional oil production, heavy crude oils will play an important role in the future. However, the use for heavy crude oil has been minimal due to the high viscosity, poor fluidity and complex composition. Therefore, how to be suitable and effective for transportation of heavy crude oil using conventional pipelines, this will be a key to the sustainable development of the world oil industry. In this paper, a favourable pipeline technique is the transport of Tahe crude oils as an oil-in-water emulsion.First of all, the effects of the types and concentrations of surfactants, alkaline kinds and concentrations, oil-water ratios, speeds of mixing, temperatures and salts on the stability and viscosity of heavy oil-in-water emulsions were analyzed by using bottle testing, spinning drop interfacial tension meter, microscope, conductivity meter, pH meter, a Turbiscan Lab expert stabilizer, Anton Paar rheometer and Zeta potential analyzer. The experimental results showed that when the oil-water ratio was equal to 7:3, the speed of mixing was 1000 r/min. the optimal mass ratio of dodecyl dimethyl betaine BS-12 and alkyl phenol polyoxyethylene ether OP-10 was 1:2, the formulated surfactant mass concentration was 1.5%, and the combinational alkali concentration was 0.2% and mass ratio of NaOH and TEA was 1:1, the water separation rate reached its minimum value 5.33% after 3 hours and the viscosity-reducing ratio was more than 96%. Additionally, the emulsion stabilized by the alkali/surfactant system possessed salt tolerance and temperature resistance.In order to further discuss the impact of these above mentioned factors on emulsion rheology, the results of orthogonal test with 3 level and 6 factors were analyzed by ANOVA and nonlinear regression using the SPSS software, with obtaining a viscosity prediction model for heavy oil-in-water emulsion. And the pressure drops of samples were calculated by the Matlab software. The results demonstrated that the effects of oil-water ratio and temperature on the emulsion viscosity and pressure drop were both prominent. On this basis, a quantitative relationship between pipeline pressure drop and viscosity of emulsion was established, and it verified that the pressure drop was proportional to the viscosity of emulsion. Therefore, in transporting the emulsified heavy crude oils through pipelines, the viscosity prediction model and the stability results of emulsion could be synthesized to optimize the emulsifying parameters. In this case, the emulsion presented a low viscosity and a high stability in pipeline. Finally, according to the related calculating formulas, the pipeline pressure drop could be predicted.Considering the water must be removed from the emulsions in the pipeline terminal, however, the emulsion stabilized by the alkali/surfactant compound system was too stabile to separate automatically. Hence, the application of chemical demulsifiers in conjunction with microwave energy was studied in this paper, and the comparative research was carried out on microwave chemical method, microwave and traditional heating. The experimental results was demonstrated that:the demulsification efficiency was higher and the separated water was clearer for the treatment under microwave irradiation with demulsifier than under microwave heating, and microwave chemical method for O/W emulsions required less demulsifier in shorter time than conventional water bath heating. The separation efficiency could attain 98.36% and the light transmittance was 72.5% under the conditions of pH=7, CRKP=0.005%, CCPAM=0.004%, and heating temperature of 70℃.Finally, since the optimal temperatures for demulsification ranged from 70℃ to 80℃, the theoretical temperature of emulsion was researched under the microwave radition. The electromagnetic distribution and the temperature field model of emulsion were established, respectively. Furthermore, the analytical solution of the electromagnetic field was obtained by the method of the variables separation, and the numerical solution of the temperature distribution was solved using the finite-difference method. Then the influence rules and internal mechanisms of microwave were analyzed theoretically. On this basis, the theoretical temperature field model and the optimal demulsification temperature range were synthesized to optimize the radiation parameters. |