Surfactant effect on air/water flow in a multistage electrical submersible pump (ESP)

Abstract

The surfactant effect on ESP boosting pressure under air–water flow is studied in this paper. A two-phase flow loop comprising a 7.62 cm diameter stainless steel liquid loop and 1.25 cm diameter gas loop is built up to conduct experimental measurements. A radial-type ESP with 14 stages assembled in series is installed on the testing bench. Pressure ports are drilled at inter-stage to measure the stage-by-stage pressure increment. The surfactant, isopropanol (IPA) is injected to change the interfacial properties of working fluids. Experiments are carried out with mapping and surging test schemes to evaluate pump behaviors at different operational conditions. ESP pressure increment under single-phase water flow agrees well with the catalog curves. For mapping tests without surfactant injection, ESP performance suffers from a severe degradation as gas flow rate increases. High gas entrainment rate causes oscillations of liquid flow rate and pump boosting pressure, featured by the instabilities of ESP operations. A sudden drop of ESP pressure increment, termed as pressure surging, occurs at the critical inlet gas volumetric fraction (GVF). For a larger rotational speed, the critical GVF is higher. With surfactant injection, ESP boosting pressure improves significantly. At different GVFs, only mild degradation is observed. Pressure surging phenomenon disappears. Further, liquid flow rate and pump boosting pressure are more stable at high GVFs compared to experimental data without surfactant injection.