Subsea Processing provides effective solutions to develop more and more challenging deepwater fieldsrnwhile maximizing oil recovery and optimizing the topsides.rnBy removing most of produced water at the seabed, a subsea liquid/liquid separation station allows torneliminate the need to transport high volumes of water from deepwater mature fields production and thenrnto debottleneck existing topside facilities and to reduce the required water treatment surface equipment.rnMoreover, the low subsea separation pressure reducing the back pressure on the subsea wellhead allowsrnfor an increase in oil recovery, which is a key driver for such a system.rnDealing with the deepwater and high design pressures constraints, the SpoolSep, developed by Saipemrnfor subsea gravity liquid-liquid separation, is made of several horizontal pipes working in parallel. The usernof small and long diameter pipes for effective gravity separation of produced water combines robustnessrnand efficiency. The pipes are designed as subsea spools which can be connected and disconnectedrnindividually for easy installation and maintenance.rnA first test campaign was performed in 2013 on a purpose built multiphase flow loop operating withrnair, water, and model oils at ambient conditions using a transparent SpoolSep model made of four parallelrnPlexiglas pipes of 200mm ID and 18m length each. Different inlet conditions, such as flowrates, water cut,rngas-volume factor, shear rate on water/oil mixtures, water residence time, and spool inclination, wererntested to qualify the separator efficiency and operability, resulting in a whole flow visualisation inside thernpipes.rnAdditional tests using several solid particle sizes were performed to qualify sand deposition andrndetermine the limits of sand transport by fluid flowing inside a single spool.rnThe paper presents the main findings of the experimental tests that validated the multiphase flowrndistribution inside the spools, levels control and symmetry. Moreover, the validation of the SpoolSeprndesign criteria regarding required separation performances is presented. Main observations and keyrnfindings on tests with sand are also described.rnThe presented work focused on the development and qualification of the fluid processing technologyrnand does not make mention of any mechanical or structural design work.
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