Abstract
Electrical submersible pumping (ESP) system performance is limited by the amount of free gas that could be tolerated before gas-locking would occur. Gas-locking of a pump generally causes a catastrophic failure of the ESP system because the pump no longer is moving fluid, which keeps the ESP from overheating during normal operation. Understanding of the phenome-non of head degradation and gas-locking in a pump is well known and has been documented and presented in numerous SPE papers in the past.
The net result of excessive gas at the pump intake is that the gas can potentially accumulate into a long continuous column in the pump, impeding the pump's ability to generate discharge pressure. Gas-locking occurs when the pump is unable to lift the fluid column in the tubing above. In cases where the pump does not actually gas-lock, at the very least the pump will suffer head degradation and low efficiency when high vapor-to-liquid ratios are being pumped. Due to the impact of free gas by volume on ESP performance, the industry has made extensive efforts to address this problem. Two important approaches have been developing technology that either separates the gas from the fluid prior to entering the pump inlet, or creating gas handling pumps which can pump larger gas by volume percentages of up to 70 percent before pump head degradation and gas-locking occurs.
Within Saudi Aramco, ESP applications have become a major contributor to meet our artificial lift requirements. In these applications, Saudi Aramco has avoided the potential issues that occur when free gas is present at the pump inlet by ensuring the pump intake pressure remains above the bubble point pressure of fluid being produced. Although this mode of operation has prevailed thus far; it is anticipated that an ever increasing number of applications will see the presence of gas at the ESP intake. Additionally, one of the leading causes of ESP failures within Aramco is directly attributable to the electrical system consisting of the packer penetrator, motor lead cable, and motor pothead.
To address these challenges, Saudi Aramco has collaborated with Baker Hughes to develop the integral pod intake (IPI) system. The IPI system is a new patent-pending concept initiated by Saudi Aramco that incorporates the shroud hanger for an encapsulated pod system as part of the intake, constructed as a single assembly including the seal, electrical penetrators, and electrical conduits extending to the seal base. This paper will discuss the background and development of the IPI system in terms of how it addresses the issues that occur when free gas is present at the ESP pump. The system's ability to eliminate the electrical integrity problem between the packer and motor pothead will also be covered. A field trial is planned to begin this year in Saudi Arabia and the results will be made available for the 2013 ESP Workshop or in earlier publications within SPE.
