Performance Monitoring of Gas Cap Blowdown (GCBD) Producers via Application of Portable Ultrasonic Meter to Safeguard Domestic Gas Supply in Northern Field X, Offshore Sabah

Abstract Northern Field X located offshore Sabah is undergoing Gas Cap Blowdown (GCBD) depletion drive to sustain domestic gas supply. GCBD Phase one began in 2022 with the conversion of two gas injectors into producers after gas injection ceased in 2019. However, the newly converted wells lack test lines for well test measurements, complicating production monitoring and optimization. Asset team deployed ultrasonic clamp-on meter as an alternative gas rate measurement of GCBD Phase One wells. To address the unavailability of gas measurements for GCBD wells, subsurface team had acquired a non-intrusive ultrasonic clamp-on gas meter. In 2022, the subsurface team took proactive measures in collaboration with metering and operations team to conduct a campaign for acquiring gas rate readings focusing on GCBD Phase one wells due to the lack of test lines on top of measuring gas rate from high-high pressure (HHP) gas producers. The portable ultrasonic meter would be clamp-on flowline near wellhead for quick and easy deployment of gas measurement. Through the collaboration of the subsurface and operations teams, the verification of the gas lift injection rate (GLIR) in Field X prompted the adoption of clamp-on meters as an alternative gas measurement method for testing GCBD Phase One wells. This initiative resulted in several value creations, including annual cost savings of USD 46.5k by replacing third-party manpower support with in-house trained technicians. This led to 100% well test compliance and facilitated the potential development of GCBD with reserves of 15 MMboe. Within a year post-first gas delivery, a total cumulative gas volume of 2.5 Bscf was secured from GCBD Phase one wells. The utilization of ultrasonic clamp-on meters for GCBD Phase one wells, despite the unavailability of test lines, enabled the asset to safeguard production and justify future development for the GCBD campaign, thereby ensuring domestic gas demand is met. The ultrasonic meter facilitates the rapid and efficient deployment of alternative gas readings for gaslift injection rate (GLIR). Innovatively, its application has been extended to measure gas rates for GCBD Phase one wells. This technology has been proven to be practical and can be utilized in future GCBD wells when testing facilities are unavailable, ensuring compliance with well test requirements.