OBERHAUSEN, Germany – Petrobras has ordered six two-stage screw compressor units from MAN Diesel & Turbo to go onto six FPSOs. Contractual partner IESA Oleo e Gas S/A has an option for two further units.
Each package compresses oil-associated gas in two stages, using a combination of SKUEL and CP oil-free screw compressor types, each of which represents one compression stage.
SKUEL screw compressors feature a horizontally split casing. They can draw in high volumetric flows at comparatively low discharge pressures. CP-type compressors, with vertically split casings, can generate roughly three times higher discharge pressures, but process lower volumetric flows.
In combination, the SKUEL stage pre-compresses the process gas but with increasing density, reducing its volumetric flow. The CP stage then increases the pressure.
In the Petrobras application, turbocompressors take the gas to a discharge pressure of more than 500 bar (7,252 psi), after which it is fed back into the borehole. Petrobras thereby avoids unnecessary emissions of carbon dioxide (CO2), common in the past as a result of flaring oil-associated gases.