ESP Performance Under Two-Phase Flow Conditions

ESP performance is affected by the presence of free gas. Two-phase performance is sensitive to intake pressure, in situ gas fraction, fluid properties, speed and number of stages. The degree of head deterioration varies from the simple reduction in the pressure increment to surging and gas locking. So far, no reliable predictive method is available to predict the performance of centrifugal pumps under two-phase conditions and to address the problems of surging and gas locking. The University of Tulsa Artificial Lift Projects is currently conducting experimental and theoretical research on the two-phase behavior of centrifugal pumps. This paper presents the analysis of experimental data for two-phase flow performance of a 22-stage centrifugal pump on a stage-wise basis. The tests were conducted at 50 Hz, varying several operating conditions such as intake pressure (50 to 250 psig) and gas flow rates. Comparison of the experimental data from this work with the homogeneous model shows that the homogeneous model is not capable of correctly predicting head degradation, surging and gas locking conditions. This work is fundamental for the development and validation of models or correlations for predicting performance of ESPs under two-phase conditions.