The Troll subsea-separation station is in operation. The station separates water and oil and then reinjects the water into a dedicated disposal well. The system is installed in the Troll field, in the Norwegian North Sea in 360-m water depth. Without the full-sized subsea processing station, the field would experience liquid-handling-capacity problems. Adapting this technology to ultradeepwater fields is a major challenge, requiring the application of radically improved methods of gravity-based separation.