Heat dissipation of the Electrical Submersible Pump (ESP) installed in a subsea skid

Jonathan Ribeiro Martins,Daniel Da Cunha Ribeiro,Fabio De Assis Ressel Pereira,Oldrich Joel Romero,Marcos Pellegrini Ribeiro

doi:10.2516/ogst/2020009

Abstract

The recent development of Electrical Submersible Pump (ESP) in the skid, installed in the seabed downstream of the wellhead in an offshore oil production system, is an alternative to the conventional system with the set installed at the bottom of the producing well, facilitating interventions in case of failure. The pump is driven by an electric motor whose cooling must be efficient to ensure the continuity of its operation. The heat withdrawal is performed by the fluid produced. The purpose of this article is to understand the process of electric motor cooling to the single-phase and turbulent flow with convection heat transfer in an annular geometry, which represents the space formed between a capsule and the ESP in the Skid system motor. With this objective it is employed a Computational Fluid Dynamics (CFD) code to solve the governing equations of the turbulent heat transfer single-phase flow. The standard κ-ε model with improved wall function (Enhanced Wall Treatment) is used to closure turbulence problem. This study considered flow rates range of 2200–4200 m3/d (representing Reynolds numbers range of 27 000–133 000 approximately), Prandtl numbers 7–37, three configurations of different annular geometries, one concentric and two eccentric, together with the condition of the constant temperature on the motor surface (130 °C) and capsule (4 °C). The simulations are validated by comparing the Nusselt number in the developed region with the Gnielinski correlation. It is observed that if the constant heat flux condition were used, the motor temperature would have lower values at the beginning and larger at the end of the geometry. Therefore, the higher the Nusselt number, the greater the heat transfer, thus intensifying the cooling of the electric motor. In the eccentric geometry a momentum transfer from the lower to the upper annular region is observed, causing the Nusselt number present an angular variation. In eccentric geometries the flow develops in greater lengths, observing that the greater the eccentricity, the greater this length. Finally, for the ESP in the Skid system the use of an eccentric geometry is not adequate.

Highlights

Conventional Electrical Submersible Pump (ESP) systems installed in deep waters (Fig. 1a) present difficulties when interventions are needed for replacement or repair, in addition to their life expectancy be relatively low
This process is observed by plotting the Nusselt number on the inner wall along the dimensionless length of the pipe, as presented by Figure 7
For the four situations the flow can be considered fully developed when x/Dh ! 10, in this condition the Nusselt number tends to remain constant for the remainder of the geometry when x = L or L/Dh = 23.36

Summary

Introduction

Conventional Electrical Submersible Pump (ESP) systems installed in deep waters (Fig. 1a) present difficulties when interventions are needed for replacement or repair, in addition to their life expectancy be relatively low. These characteristics lead to a significant downtime of production. According to Tarcha et al (2015), one of the proposals was the development of an ESP out of the well, installed in According to Takács (2009), one of the problems that occur in the ESP system is the high heating of the electric.

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Conclusion