Abstract

The one-dimensional model proposed by Sun and Prado [1, 2] to predict Electrical Submersible Pumps (ESP) head performance under gas-liquid flow conditions has been improved with a new correlation for the ratio of the drag coefficient (Cd ) to an interfacial characteristic length ( r interfacial). This study has found the ratio, Cd/r interfacial , is also a function of channel rotational speed in addition to gas void fraction and other parameters. The paper summarizes the model with detailed wall frictional equations and addresses its implementation procedure from a manufacturer’s available single-phase catalog data to the predicted two-phase head performance results. The implemented algorithm is especially effective to obtain the ESP head performance under two-phase flow conditions. The study is beneficial for the appropriate design, simulation, and troubleshooting of ESP installations in a two-phase environment.

The model has been used to compute results and perform sensitivity analysis under different two-phase flow conditions: pump intake pressure, gas void fraction, gas flow rates, rotational speeds, Cd/r interfacial , and wall friction effects, respectively. The sensitivity analysis has been used to determine the correlation for the ratio of  Cd/r interfacial during model development.

The comparison of the model results against the experimental data, except at a low gas void fraction with a low liquid flow rate, shows good agreement. The new model gives an excellent prediction for different shaft rotational speeds compared to Zapata’s partial gas-liquid data of ESP [3]. However, further validation with more experimental data is needed.

Introduction

ESP’s are often installed in a gassy environment with different pump frequencies, intake pressures, intake gas void factions, etc. The effects on ESP performance from these aspects suggest further study. Single-phase pump performance, Beltur’s gas-liquid experimental data at 50 Hz [4], and Zapata’s partial gas-liquid data at different frequencies [3] have been used in this study. This paper highlights the extension and improvement of the gas-liquid head performance model [1, 2] of electrical submersible pump.

Literature Review

The experimental approach for ESP performance under gas-liquid flow conditions can be found in Pessoa [5], Beltur [4], Duran [6], and Zapata [3] among others. The modeling approach can be found in Sachdeva [7, 8, and 9], Minemura [10], and Sun [1, 2, and 11] among others. Sachdeva’s model and Minemura’s model were based on and improved in the previous model [1, 2].

Two-Phase Model of ESP’S

This section summarizes the two-phase model developed for the prediction of ESP head performance. The detailed model with assumptions can be found in Sun [1, 2] except for the improved correlation of  Cd/r interfacial, which is presented in this paper.