CFD Simulation of ESP Performance and Bubble Size Estimation under Gassy Conditions

Abstract

Abstract As a high-efficiency tool to convert rotating kinetic energy to hydraulic pressure head, the electrical submersible pump (ESP) is widely used in the petroleum industry to increase hydrocarbon fluid production rates. Previous studies showed that the presence of gas would cause ESP hydraulic head degradation. Flow behaviors in ESPs under gassy conditions, such as gas pockets, further deteriorate ESP performance. It is important to investigate flow structure inside ESPs with gas involvement. In this paper, we use Computational Fluid Dynamics (CFD) to simulate fluid flows through an entire ESP stage, including impeller and diffuser. We also calculate the corresponding heads under both liquid and gas-liquid flow conditions. Additionally, the pressure field, velocity profile and gas distribution inside ESPs are analyzed. The commercially available CFD software was used for geometry editing, mesh generating, finite-volume-method solving and post-calculation. Sensitivity analysis of meshing was also conducted. The CFD simulation results of ESP performance under single-phase water conditions matched manufacturer performance curves. For two-phase flow simulation, water and nitrogen were used as working fluids with different gas volume fractions (GVF) from 1.0% to nearly 20% and considerable degradation of pump performance was observed. In contrast to previous simulations in the literature using constant bubble sizes, our simulation results reveal that bubble size is a key factor related to an increase in GVFs. The CFD simulation results were compared with experimental measurements from the Tulsa University Artificial Lift Projects (TUALP) and good agreement was achieved under both single and two-phase conditions. The observed results using proper bubble size estimation indicated that CFD simulation is a reliable tool for analyzing ESP performance.