Effects of gas volume fractions on electrical submersible pump performance under two-phase flow

Abstract

An Electrical Submersible Pump (ESP) is the most commonly used artificial lifting method in the oil and gas industry through conversion of kinetic energy to pump pressure head; however, issues like gas entrainment and shifting production rates tend to cause ESP pressure degradation. Flow behaviours inside the ESP, such as gas pockets or pressure surging tend to diminish the pump pressure head significantly. Observation of gas-liquid flow in the ESP is challenging due to the compact, sophisticated geometry and highly turbulent flow strucutres. This paper observes two-phase flow in the ESP through CFD simulation, and illustrates its pressure degradation through Air Volume Fraction contours showing formations of gas pockets and recirculation bubbles. This research utilized Mixture Flow as its main two-phase model with 1%, 6% and 10% Gas Volume Fraction (GVF) ratios inside the pump at a constant flow rate of 250 L/min. The results show a clear pump head degradation from 3.062 m to 2.251 m overall. The centrifugal pump under two-phase flow is not able to generate the same amount of pressure head as it normally does due to the bubble point pressure and this decrease in pump pressure head is a potentially unstable behaviour, which is acknowledged as pressure surging.