Experimental Testing of an Electrical Submersible Pump Undergoing Abrasive Slurry Erosion

The Electrical Submersible Pump (ESP) manufactured by Baker Hughes, model no. WJE-1000 is designed for wells that are expected to have a high content of abrasive solids. It is a mixed flow, tandem compression type pump. Although the erosion of the pump diffuser and impeller stages are significant, the ESP study shows that the most sever failure is due to components that affect the pump?s rotor dynamics such as radial bearings and impeller seals when eroded with 100 mesh sand. Erosion of these seals will result in an internal leakage that can significantly affect stage pressure rise, efficiency, power consumption, vibration, pump life and running cost.

The erosion study utilizing 100 mesh fracture sand at 0.2% concentration, with the pump operating at 3600 RPM, 40 PSI intake pressure, 1150 GPM for over 117 hours comparisons are made to the pump?s baseline performance. Measurements of the rotor bearings, impeller seals and their corresponding stators showed that the wear patterns generally increase with time and differ by location. Stage 1 bearings and seals suffered the least amount of erosion and stage 3 rotor components suffered the most erosion. The maximum change in stage 3 bearing clearances was 223% and the maximum change in stage 3 impeller seal clearances was 300%. Performance wise the total pump efficiency dropped by 6.77%, the total pressure rise dropped by 6.3%, the pump?s best efficiency point decreased by 0.78%, and the power consumption increased by 0.49%. Pump vibration patterns also changed with time and by location. The maximum shaft orbit diameter was at stage 3 and it grew 643% in diameter after 117 hours of erosion. The waterfall plots of the pump?s ramp up changed significantly with time. After 117 hours at 3600 RPM, sub-synchronous oscillations at 67% of the synchronous speed dominated the amplitude peaks showing that the rotor vibration locked with the rotor?s first natural frequency at around 2500 RPM. After 117 hours, another sub-synchronous started showing a peak at the rotor?s second natural frequency at 1500 RPM.