Comprehensive Preparations for FPSO Disconnection: Ensuring Safe and Environmentally Responsible Decommissioning of BJSA Subsea Systems

Abstract The objective of this paper is to navigate through the preparatory works for the FPSO disconnection operations, including flushing the subsea system and isolation of the wells/XTs (Christmas Trees). The BJSA subsea system comprises three production manifolds, each connected to the FPSO via flexible risers/flowlines all looped back to the FPSO. Each manifold is equipped with four XTs connected by gas lift and production jumpers. In preparation for riser disconnection, a comprehensive flushing of the subsea system was performed, covering oil/gas lift systems and umbilicals. The gas export decommissioning posed additional challenges due to the absence of a loop back to the FPSO. Final subsea preparations for riser disconnection included isolating all XTs, which consisted of the disconnection of the jumpers and installation of additional physical barrier at the XT hubs (production, gas lift, or water injection). Most importantly, all scopes were delivered safely and reported no hydrocarbon leak to the environment.