Abstract
Head deterioration observed in electrical submersible pumps under two-phase flow is mild until a sudden performance breakdown is observed in the pump head curve at a certain volumetric gas fraction. This critical condition is termed surging. Consequently, the two-phase pump head is associated with whether the stage operates under conditions prior (mild performance deterioration) or after (severe performance deterioration) the surging point.
The surging, for engineering purposes, can be predicted by published correlations, but the lack of theoretical basis is a limiting factor for their application. Mechanistic models seem to be the proper alternative. But, the poor understanding of the physical mechanism that causes the surging hinders the development of such mechanistic models. This paper reviews some of these correlations and mechanistic models by comparing its predictions against experimental data acquired in a closed loop with water and air utilizing a commercial 24 stages ESP. The data cover a wide range of volumetric gas fraction, rotational speeds and intake pressures. As consequence of this analysis, two correlations have been formulated. The first correlation predicts the surging as function of rotational speed and fluid properties, while the second correlation intends to predict the homogenous boundary. This boundary encloses a regime in which the homogenous model works for predicting the ESP head curve.
