Modelling the dynamical behavior in Electrical Submersible Pump (ESP) for liquid-liquid flow

Abstract

In oil exploitation, the industry frequently has to increment energy to the fluid in order to reach the final destination. This is a requirement from increasing the production in bursting wells to wells that are unviable without the energy increment. Despite the increase in production in bursting wells, the energy increment is also associated with the well depletion. In these cases, as the oil is extracted the well pressure reduces and thereby the production is reduced. The fluid energy increment in the oil industry is called artificial lift. There are various methods which are recommended for certain well conditions. In this context, there is the Electrical Submersible Pump (ESP), which is the second most used method in the world, with 10% of the oil global production. This method is composed by a centrifugal pump of several stages, installed inside and at the bottom of the pipeline. However, in production conditions, the ESP faces multiphase flows and high viscosity oil that affects negatively the ESP performance. This factors can reduce and even stop the production in certain conditions. Thus, there are works in the literature that attempt to understand the two-phase and also the high viscosity flow inside the multiple stages of the ESP. Those works usually use computational simulation in order to draw some conclusions. Moreover, most of the works have as objective the pump characteristic and efficiency curves of the pump operating under multiphase and high viscosity flows. Furthermore, there are works that study the effects of the emulsion formation and its phase inversion inside the ESP on the characteristic and efficiency curves. Nonetheless, despite the invaluable information from these curves, they only consider the ESP steady-state behavior. In this context, few works try to understand and model the ESP dynamical behavior operating under multiphase flow, high viscosity and emulsion formation. The modelling is crucial to develop the automatic control of the ESP and the production. The controllers could optimize the production according to a pre-established criterion and reduce the necessity of human intervention in the ESP control. Besides, by modelling the ESP it is possible to avoid the ESP operation in unstable points that could damage the ESP. Thus, the main interest of this work is to model the dynamical behavior of the ESP under liquid-liquid flow and the effect of the emulsion formation. The dynamical behavior modelling of a system can be based on experimental data or by using analytical models. However, techniques based on experimental data can be limited to the system used. Once despite describing a system accurately, it is not guaranteed that it will describe a similar system reasonably as well. On the other hand, an analytical approach that aims to describe the many physical phenomena that occur can be more reliable to similar systems. As the ESP is a complex system with different physical domains involved, for instance, the electrical, mechanical, hydraulic, etc., the modelling technique bond-graphs can be considered one alternative to model and identify the ESP. Finally, the objective of this work is to develop a computational simulator of the dynamical behavior (considering transient effects) of the ESP operating under multiphase, high viscosity flows and emulsion formation. These phenomena are complex and not well-known inside the ESP, featuring the challenge of this project. (AU)