Modal parameters estimation of an electrical submersible pump installed in a test well using numerical and experimental analysis

Abstract

Modal parameters of an Electrical Submersible Pump (ESP) installed in a test well were numerically and experimentally identified. The numerical model was developed using the finite element method. All the masses and stiffness elements necessary to evaluate the lateral vibration of the equipment were considered, as well as the hydrodynamic added mass effect. In the experimental test, an impact hammer was used for exciting the ESP structure near the wellhead, in the production pipe, and not directly at equipment frame. Vibration signals along the ESP were acquired and Eigensystem Realization Algorithm (ERA) method was used to identify the modal properties. Results showed the impact test as a useful method for modal parameters identification of ESP's installed in a test well. However, due to the location where the impacts were applied, the lower vibration modes, outside the operating range, were not excited. On the other hand, the natural frequencies numerically identified were overestimated in comparison with those obtained experimentally.