Water-in-oil emulsions usually present complex rheological behavior that depends on the physicochem-ical properties of both phases, the presence of surfactants, and the flow conditions. Thereby, this paperaims to propose a criterion to characterize the rheological behavior of stable and unstable water-in-oil emulsions within the centrifugal pumps. This criterion is based on the slip ratio between the dispersedand continuous phases. For this, the droplet size distribution was measured at the ESP outlet and the slipratio was estimated based on the centrifugal buoyancy-induced flow. A new model was proposed todetermine the Sauter mean diameter for different systems of the water-in-oil emulsion flows withinthe ESP based on operational conditions, which presents good agreement with the experimental data(12.6% of error). Finally, a new dimensionless number parameter named Slip Relevance number was pro-posed to separate the different emulsion flow behaviors within the ESP and its critical value was obtained.
Tag: Unstable emulsion
Experimental investigation on the performance of Electrical Submersible Pump (ESP) operating with unstable water/oil emulsions
Electrical Submersible Pump (ESP) is one of the most commonly used artificial lift methods in petroleum production, due to its capacity to operate in several conditions with two or three-phase flows. When the ESP operates with emulsion flow, its performance is degraded, and operational instabilities occur. Therefore, this paper aims to carefully investigate phase inversion and to present, by the first time, the ffective viscosity of unstable mineral oil/water emulsions, both within the ESP. The first part of this work analyzes the phase inversion phenomenon for two oil types in three viscosities, five ESP rotational speeds, and three mixture flow rates. Logistic functions were fitted using the dimensionless head as a water cut function to determine the phase inversion within the ESP. The continuous phase inversion model, developed for emulsion pipe flow, did not present a satisfactory agreement to flow conditions tested. An indirect method to determine the emulsion effective viscosity within the ESP was proposed, which was obtained from the water/oil emulsion performance curves. The viscous performance data were used to determine the geometric coefficients of a dimensionless head empirical model for the tested ESP. Thus, the calculated values were compared with the effective viscosity obtained with oil and water emulsions, as well as the ESP performance, operating with emulsion and oil, which provides similar values for low rotational speeds. The different behavior of the effective viscosity between the pipeline flow and within the ESP was observed for water-in-oil emulsions and may be related to the high centrifugal field in the ESP.