Seawater injection is a common practice for maintenance of reservoir pressure. A compact seawater deoxygenation system using regenerated nitrogen gas was introduced for offshore facilities in 1992. The original systems were based on a serpentine tube co-current mixing system. Due to the requirements of floating facilities to meet smaller footprint and weight, and to meet motion criteria in floating facilities, the third-generation system employs static mixers and a simplified control strategy. Based on experience from recent installations in offshore Thailand and Norway, troubleshooting guidelines are presented for operating turndown and debottlenecking scenarios.