Modal Parameter Identification of an Electrical Submersible Pump Installed in a Test Well Using Drop Tests

Abstract

Electrical submersible pumps (ESPs) are used in the petroleum industry to pump large amount of fluids from subsea deep wells. Currently, ESPs are responsible for approximately 10% of the world’s crude oil production. When high flow rates are required, gas lift and the ESP are the only available technologies that can be applied. ESP systems are much more complex and less reliable than the gas lift method, but they are more efficient and able to yield higher flow rates and pressure. ESPs are installed inside or near production wells, with the entire auxiliary infrastructure for power supply and control system. This means that maintenance is prohibitive because of production losses and the need for expensive and unavailable drill ships. In order to increase ESP’s reliability, is highly important to know the equipment dynamic behavior while it is operating. The objective of this work is to identify the modal parameters of an ESP with 62 stages and 10.42 m in length, weighing 616.8 kg and installed 9.02 m deep in a test well circuit using water as working fluid. Drop tests were carried on and the vibration responses collected by water proof accelerometers were used to perform an output-only modal analysis using the Enhanced Frequency Domain Decomposition (EFDD) technique. Results were compared with modal parameters obtained using impact tests and showed that the drop test is an useful method for modal testing of ESP’s in test wells.