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Based on previous experiment result, an assumption is made to explain the abnormal head degradation in the first stage of an electrical submersible pump (ESP): the bubbles' breaking up and coalescence effect with compressibility is the main reason of this phenomenon. To investigate the head degradation problem inside the ESP, a series of numerical simulations are performed on the first stage of the split-vane impeller pump commonly employed for gas handling purpose. These three-dimensional transient Eulerian multiphase simulations are divided into two groups: one group with the traditional fixed bubble size method and the other with the ANSYS population balancing model (PBM) allowing the bubbles to break up and coalesce. The simulation result with the changing bubble size matches well with the experiment data, which supports the previous assumption. The flow field based on PBM simulation is visualized and analyzed. Also the separation of phases is discovered with large volume of gas accumulating at the suction side of the impeller trailing blades, which is also supported by experimental observation.

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Electric submersible pumps (ESPs) provide artificial lift within oil wells. ESPs commonly fail from mechanical vibrations that increase as bearing clearances increase from debris, gas, and liquid pumped through the ESP. In order to understand journal bearing wear within an ESP, three stages of a mixed flow electric submersible pump were subjected to hydraulic fracture sand slurry in water. One hundred seventeen hours were conducted with sand and water, followed by 68 h with air added at 15% inlet gas volume fraction. The journal bearings were severely worn by the end of testing, and pump vibrations increased with increased bearing clearances. Bearing vibrations and clearances became significantly larger than the impeller labyrinth seal vibrations and clearances, indicating that the labyrinth seals became the dominant rotor support once the bearings were worn. Adding air increased the wear and rotor vibration orbit variability. Rotor vibration orbits were entirely independent of gas void fraction by the end of testing, indicating that the lubricant composition no longer directly impacted vibrations. Fine axial cracks from heat checking were observed on the journal of the bearings. Results indicate that controlling journal bearing wear is a critical factor for increasing operating lifetimes. Alternative bearing geometry and materials should be investigated to prevent the occurrence of three-body abrasion, limit the resultant wear rate from three-body abrasion, and limit the damage from heat checking.

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