Alternative Method to Supply Pneumatic Air to an Unmanned Platform, In the Event of the Platform’s Instrument Gas System is on Downtime

Abstract

Abstract D-C is an unmanned, pneumatic operated wellhead platform located offshore Sarawak, Malaysia. D-C consists of oil producer and water injector wells, instrument gas system and four pipelines connected to a manned mother platform D-A which is around 2 nautical miles away. The four pipelines are dedicated for gas lift, High Pressure (HP) production, Low Pressure (LP) production and water injection respectively. Pneumatic supply medium for D-C is natural gas, tapped from the gas lift pipeline, which is supplied from the gas lift compressor at D-A. D-C does not have power generation system hence solely depends on instrument gas to energize the instrumentation. In 2019, the instrument gas scrubber on the platform experienced severe corrosion and was sent back to shore for repair, resulting in the natural gas was unable to be channeled to the platform’s instrumentation. This caused the platform to be on unplanned shut down. As D-C is an unmanned facility, a portable air compressor cannot be used for continuous pneumatic supply, as mechanic and fire watcher will be required to be onboard day and night. Hence, an alternative method of supplying pneumatic air for D-C was executed which enabled the platform to be back online without instrument gas scrubber, and in compliance to its unmanned philosophy. Compressed dry air was exported from D-A to D-C via the HP pipeline, and the air from the pipeline was supplied to the pneumatic instrumentation system of D-C. To achieve this, the HP pipeline was de-oiled and continuously pressurized by compressed air which was supplied by portable instrument air compressor at D-A. The compressed air in the HP pipeline was used to supply pneumatic air to the instrumentations at D-C. D-C was successfully operated continuously albeit with minor production deferment (some wells were closed in to minimize back pressure at the LP pipeline due to HP pipeline is unavailable for the wells), throughout the duration of instrument gas scrubber unavailability onsite (around one month). Threat of prolonged total production interruption from D-C was successfully eliminated and production from the platform was partially recovered.