Oz is an offshore oil field with Electric Submersible Pump (ESP) as the main artificial lift system. Gassy well condition becomes a key challenge in this field as some ESP wells trip due to pump gas locking which leads to production deferment and ESP failures. The exploration for solutions to improve well performance by avoiding gas-locking conditions has gone through a steep learning curve and many adjustments since ESP firstly installed in Oz field. Starting from widely used conventional gas handling equipments such as gas separator and gas handler to application of multiphase pump on the ESP system. But none of those equipments have effectively eliminated gas-locking condition in some wells. This paper will present a new approach at Oz field to improve well performance by implementing bottom feeder intake application on electric submersible pumps in gassy well.
To analyze this problem, well production simulations were performed and found out that flow pattern on the lateral section or below the ESP completion was slugging at some well conditions. Due to the slugging flow pattern, the fluid hold up in the annulus might be reduced up to 30%. A large amount of gas volume will enter the pump when the slug reaches the pump intake. In such a case, neither gas separator or gas handler is able to separate the gas or condition the flow before going into a pump, which leads to the gas-locking condition in the pump. Bottom Feeder Intake (BFI) was proposed as a unique and versatile solution to handle gas when slug flow pattern occurs in ESP wells, which effectively reduces gas-locking condition on ESP and subsequently improves well performance on those problematic wells.
Electric submersible pump with combination of gas separator and bottom feeder intake were first successfully installed in several wells in 2016 and currently are still running. The combination of bottom feeder intake and gas separator have been progressively installed on some problematic wells since then. This application significantly minimizes gas-locking problems, avoids cyclic shutdowns, increases ESP service life, reduces deferred production activities and gives opportunities to increase the production from ESP wells. Through well production simulation and analyzing the effect of fluid flow pattern below ESP completion to pump gas-locking symptom, bottom feeder intake has been chosen as an effective solution to minimize gas-locking in gassy well.