Marginal specialist branches out from multiphase to subsea separation

Framo Engineering's multiphase booster pump.

With field developments moving to ever more remote locations, deeper waters and further from existing infrastructure, the need to add pressure energy to the unprocessed wellstream becomes increasingly important.

For over a decade Framo has been working on multiphase booster pumps for topsides and subsea installations. The most advanced of these concepts is the Framo multiphase helico-axial pump, based on the rotodynamic principle developed in the Poseidon project by Statoil, Total and IFP. In 1992 they rewarded Framo with a worldwide license covering use of the Poseidon hydraulics.

Two different pump prototypes of the first generation Poseidon hydraulics have been extensively tested using Framo's multiphase test facilities. The pumps are now used commercially subsea on Norske Shell's Draugen Field (installed August 1993) and topside on Statoil's Gullfaks A platform (since February 1994).

Subsea electrically-driven multiphase pumps will also be installed on BP's North Sea ETAP multi-field development, Mobil's Topazio deepwater satellite development offshore Equatorial Guinea and on Statoil's Lufeng Field in the South China Sea, where five plus one 400kW pump units will be deployed in 330 meters of water.

Framo's multiphase flow meter is designed as an alternative to conventional separator systems for measurement of oil, gas and water. According to Framo it is less expensive, less space and weight-intensive, more accurate and easier to use.

This is the only meter employing a fully physical metering principle and an inherent calibration method, thereby avoiding the use of empirical relations and test separators for calibration. The insert design of the subsea meter is also important towards cost-effective deployment and maintenance in subsea applications.

To market and further develop this technology, Framo, Daniel Measurement and Control and Schlumberger's Wireline and Testing division recently agreed to create a jointly-owned technology center in Bergen, known as 3-Phase Measurements. The center will be staffed by specialist personnel from each company designing, manufacturing and installing multiphase flow meters in topside and subsea configurations.

For the floating production sector, Framo has developed and qualified a compact, multi-path swivel design for high pressure and temperature applications. The submerged turret production rotating connector extends the highly successful STL technology into a turret mooring system for FPSOs and storage.

The compactness of the Framo swivel allows for inclusion of several high pressure risers and umbilicals, and handles the interface between the subsea wells and process plant on the vessel. The swivel design and technology has been qualified for an increased number of risers and flow capacity and also increased pressure rating. These features should provide a standalone swivel system suitable for almost any FPSO application.

New projects incorporating this concept are Norsk Hydro's Njord Field, Statoil's Lufeng and Connemara fields, Enterprise's Pierce and Petronas' Malong/Sotong/Anding (MASA) developments.

Finally, in partnership with ABB, Framo has helped develop the subsea separation and injection system (SUBSIS). This concept involves removal of bulk water from the wellstream at the subsea installation. The water is then reinjected using Framo pumping technology derived from development over the past decade of the electrically driven subsea multiphase booster system (ELSMUBS).

SUBSIS will make its debut on Norsk Hydro's Troll C project, featuring the world's first subsea water injection pump, rated at 1.8MW.

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