Deepwater Production

Extending the use of gravity-based separators for deep and ultradeep water

Troll was the first and remains the only field to use subsea separation. But given its inherent advantages, it will likely become a major target for industry development

Jarle Michaelsen, ABB Offshore Systems Inc.

The Troll subsea separation station is the only full-size, subsea separation station installed, operating and establishing a working track record. The station separates water and oil, re-injecting the water into a dedicated disposal well. Troll field is located in the Norwegian North Sea in 360-m (1,180-ft) water depth. The field would experience liquid-handling capacity problems if not for the subsea processing. Adapting this technology to ultra-deepwater fields is a major challenge, calling for radically improved methods for gravity based separation.

To meet the demands of future deepwater fields, some radical changes will be necessary to adapt subsea separation to ultra-deepwater fields, and to do so at acceptable levels of risk. This article focuses on this challenge, and describes principles that can be used in the next generation of deepwater and ultra-deepwater subsea systems.