Predicting ESP Motor's Overheating Due to High Free Gas Fraction

Abstract

Electrical Submersible Pump (ESP) is one of the most adaptable artificial lift methods that is capable of lifting high fluid volumes from wellbore to surface. Despite that, ESPs are not suitable for wells with high gas liquid ratio. Presence of free gas inside an ESP causes pump performance degradation which may lead to higher motor temperature and/or pump failures during operations. Thus, it is necessary to investigate effects of free gas on pump failures due to the degradation of pump performance under two-phase flow and high motor temperature. This study is one of the first attempts to simulate motor temperature using developed correlations which predict two-phase pump performance under downhole conditions. Field data from two ESP-oil wells were used to confirm the reliability of the developed simulations predicting two-phase ESP performance and motor temperature under downhole conditions. The simulation results show that liquid rate drops significantly due to the degradation of pump performance under two-phase flow, reduces by around 50% when free gas fraction increases from 0 to 0.4. In addition, ESP applications might be feasible in different gassy conditions with up to 0.35 free gas fraction. However, when the pump is run at 3500 RPM, the maximum free gas fraction that an ESP can tolerate is about 0.25 before the pump is overheated and failed. The findings from this study will help operating companies as well as ESP manufacturers to operate ESPs within the recommended range under downhole conditions.