Studies On Mechanism Of Combination Of Demulsifier And Electric Field Demulsification

The stability of crude oil emulsion and preparing parameters were studied in this paper. Rotating rate and emulsifying time were determined to prepare crude oil emulsions. Stability of crude oil emulsions decreased as water conductivity and temperature increased. And the rheology of these crude oil emulsions was also studied by using Brookfield DV-II+ Viscometer in this paper. The results demonstrated that in the range of shear rate studied, the crude oil emulsion behaved as Bingham fluid when temperature was lower than 50℃, and the crude oil emulsion behaved as Newtonian fluid when the temperature is higher than 50℃. The theoretical equation for describing the rheology of crude oil emulsion was founded.Using the above crude oil emulsions, mechanism of ten types of demulsifiers with different structures such as AR36 was discussed. The results were that demulsifiers AR36, AE9901 and TA1031 were more effective on these crude oil emulsions. Magnitude sequence of dehydration ratio of demulsifiers with different structures varied as the water conductivity in crude oil emulsions changed; and combination of demulsifiers was benefit to demulsify crude oil emulsions. Moreover, the mechanism of demulsifiers with different structures was that the locations of PO and EO groups in demulsifiers chains and the number of PO and EO groups were different for different structures demulsifiers, resulting in different dehydration ratio. As for branched chain demulsifiers, interspace of molecules was smaller than that of straight chain demulsifiers, opportunity that active substances entered interspace to form mingled adsorbing film was less, which could decrease intensity of oil-water interfacial film in a greater extent. So the crude oil emulsions were demulsified easily.Finally, regulations of combination of demulsifier and electric dehydration were discussed using DPY-2A Demulsifier and Electric Dehydrating Performance Measurer. It showed that the lower the water cut of crude oil emulsions, the smaller the dehydration ratio; effectiveness of combination of demulsifier and electric field was better than that of single electric field, and there was a optimum demulsifier concentration. Using CIR 100 Interfacial Rheometer to measure interfacial viscosity, mechanism of combination of demulsifier and electric field was that demulsifier molecules adsorbed at oil-water interface, displaced the natural emulsifier molecules, which decreased interfacial viscosity, thus coalescing resistance was reduced; on the other hand, under electric field, pores appeared at interfacial film, when the intensity of electric field surpassed the critical value, the interfacial film ruptured, and water droplets began to coalesce. In AC electric field dipoled coalescence and oscillating coalescence functioned mainly, and in DC electric field dipoled coalescence and electrophoresis coalescence acted chiefly.