Reducing Gas Lock Downtime on Mariner ESP's

Abstract Gas locking of ESPs on Mariner has been the largest loss source in the field's production history. In 2020 and 2021, approximately 50% of all production deferments were associated with gas locking events. Fast-forward to Q3 2024, no gas locking deferment was recorded, despite increased liquid offtake from the reservoir and an ongoing drilling campaign. This improvement in uptime has been attributed to 3 main factors: Focus on Water InjectionIncreasing injector uptimeIncreasing the injector well countEnhance the selection of ESP gas handlersAdvanced Gas Handler (AGH) vs Multiphase Gas Handler (MGH)Development of ESP Automatic Control System (ACS) While key to the Mariner field, the benefits of water injection will not be discussed in detail in this paper. Comparing analogue wells, we can see the impact of a robust gas handling device on ESP operability. Despite changes to the water injection philosophy and ESP design, all gas locking issues have not been engineered out. Legacy systems still suffer from legacy gas locking problems. Variability in the Mariner reservoir & fluid quality also makes pre-drill production rates difficult to predict. To counteract these issues, ACS was developed. A combination of current control mode, intake pressure control mode, and "dual control" mode (a hybrid of current and intake pressure control mode) has been rolled out across the field. A recent case study from the field has shown an increase from 75% to >90% uptime on a troublesome ESP with the implementation of ACS. By considering both the design and operation of Mariner ESPs alongside the reservoir management philosophy, the production impact of gas locking ESPs in a challenging, heavy/viscous oil environment has been massively reduced.