Sand production occurs from wells commingled with crude oil and produced water. For a subsea separation unit, the produced sand concentration as well as the particles size and the subsea equipment design are the main parameters to be considered when designing the most suited sand handling system. A sand management philosophy has then to be defined case by case. Within a subsea produced water separation station using the Saipem SpoolSep for bulk separation, the sand could be handled at several production points using different technologies and approaches:
Upstream the bulk separator using multiphase desanding systems allowing the removal of the largest particles from the well stream.
Inside the SpoolSep, which is designed considering a sand-dedicated volume to ensure the required separation performances even if a sand bed is formed, knowing that the modularized spools could be replaced if needed. Moreover, if necessary each spool could be flushed to remove settled particles by fluid flowing.
Within the produced water treatment stage, downstream the bulk separator where cyclonic desanders could be used to achieve the water quality specifications in terms of SiW concentration and particle cut off diameter.
The slurries coming from the different stages (multiphase desander, bulk separator, water treatment) could be exported continuously through the multiphase line up to the surface facility using ejectors or specific pumps or could be stored subsea before export.
The paper presents the sand management philosophy and technologies which could be used in a subsea separation unit with the SpoolSep for bulk separation of produced water.
