Modeling of the Phase Inversion Point of Crude Oil Emulsion by Characterization of Crude Oil Physical Properties

Accurate prediction of the phase inversion point (PIP) of crude oil emulsion (COE) will give important guiding significance to the mixed transportation technology during the crude oil mining process. The influence of water cut of a system on viscosity characteristics of the COE was studied by emulsification experiments with 16 kinds of crude oils having significant differences in physical properties. The results showed that under the condition of low water cut of a system, the crude oils can emulsify all the water to form stable W/O emulsions with apparent viscosities much higher than those of pure crude oils. When the water cut of a system exceeds a certain critical value, the crude oils have no ability to emulsify all water; instead, they are wrapped by a water phase and form unstable O/W emulsions, and their apparent viscosities decrease sharply compared with those of pure crude oils. The critical water cut of a system corresponding to the abrupt change of apparent viscosity of the COE is the PIP of the COE changing from the type of W/O to O/W. Furthermore, the apparent viscosities of stable W/O emulsions decrease with increasing shear rate and temperature and meanwhile increase dramatically with the increasing water cut of a system. The apparent viscosities of unstable O/W emulsions decrease with increasing shear rate, water cut of a system, and temperature and are far lower than those of pure crude oils. Four typical parameters were chose as the representation to describe the crude oil physical properties (COPPs), that is, the content of saturates, the content of aromatics, the content of surfactants, and the crude oil acid number. On the basis of the quantitative description of COPPs, a prediction model for the PIP of the COE was established. The results of model verification showed that the mean relative deviation of prediction results was 2.9%.