ESP Optimization Goes Further: Operating Frequency Beyond 60 Hz

Abstract

Optimization in brown field developments is always challenging in terms of cost. One of it is XY Field, Rimau Block, South Sumatera with more than 70% of artificial lift is Electrical Submersible Pump (ESP). At ESP wells that are already running at maximum operating frequency of 60 Hz, some are still having problems to optimize their potential. The option to replace the pump with a higher rate is less of an option due to high cost. This leaves an opportunity to gain oil production by increasing frequency above 60 Hz. Upon discussion with the ESP Principal on the risks and possibilities, a trial was then planned for 3-wells. Candidates are selected from the list of ESP wells with the following criteria such as already operated at 60 Hz, still have sufficient fluid submergence, and based on simulated motor load at 70 Hz is still at safe motor load level. Frequency was increased gradually while continuously monitoring ESP Parameters (motor load, voltage and harmonic). It is also necessary to monitor the cable temperature as it is directly affected by the frequency changes. For each frequency increment, a well test is also performed to monitor the production changes. The trial was done on 3-wells (XY-364, XY-370 and XY-378), with the following promising results. XY-364 and XY-378 successfully reached the targeted 70Hz, while XY-370 stopped at 65Hz due to a cable temperature issue. Oil gain from this optimization was 48 BOPD with 1,043 BLPD and similar BS&W profile. ESP operation still normal until present day with all parameters at acceptable range. There were, however, challenges found during the trial. Cable temperature of XY-364 increased at junction box and found cable scun loosen. The problem was solved by replacing the cables. For XY-370, found temperature increment at moulded case circuit breaker during trial at 65 Hz. It was decided to hold at existing frequency. Unbalanced motor load at XY-364 and broken capacitor at XY-370 occurred at Harmonic Filter. The problem was solved by replacing the capacitor. The trial proves that we can operate ESP higher than base frequency (60 Hz) and resulted in decent oil gain. This opens an opportunity in ESP optimization above 60 Hz at an even larger scale.