WATCHING THE WORLD SUBSEA INNOVATIONS HIGHLIGHT ONS

With David Knott from London A feature of the Offshore Northern Seas exhibition, which takes place in Stavanger every 2 years, is the award of a coveted prize for technical ingenuity. The 1992 ONS Innovation Award went to Kvaerner Energy AS, Oslo, for its booster station concept for subsea oil and gas production. This is designed to enhance production from declining fields or use in field development projects that might otherwise be unprofitable.

Sept. 7, 1992

3 min read

A feature of the Offshore Northern Seas exhibition, which takes place in Stavanger every 2 years, is the award of a coveted prize for technical ingenuity.

The 1992 ONS Innovation Award went to Kvaerner Energy AS, Oslo, for its booster station concept for subsea oil and gas production. This is designed to enhance production from declining fields or use in field development projects that might otherwise be unprofitable.

The Kvaerner booster station (KBS) avoids the problems of multiphase solutions by splitting the well stream into liquid and gas phases. This yields better flow characteristics in rotating machinery, freedom to route oil and gas separately, continuous well testing by metering the separate discharge lines, and ability to choose the best equipment characteristics for a single fluid in a pipeline.

It consists of three modules: separator, pump, and compressor. A typical installation would be in a field producing 25,000 b/d of oil and 4,000 cu m/day of associated gas with a required pressure rise of 40 bar in boosting.

GAS-FILLED MOTOR

One of the problems that has dogged other multiphase and subsea concepts has been the vulnerability of electric motors in seawater operation. The KBS has a specially developed gas filled electric motor driving the compressor, using process gas to help maintain sealing. The motor is an 830 kw AC unit developed by Loher AG of Ruhstorf am Rott, near Munich, Germany.

A KBS prototype is to undergo integration testing, starting this month for completion during autumn, at the Sintef laboratory in Trondheim, Norway. If tests are successful, fields trials will follow.

AKER BOOSTER

Kvaerner's main competition in subsea boosting, as in most other markets, comes from Aker Engineering AS, Oslo.

The Aker booster separates and boosts the well stream but avoids the use of rotating machinery by utilizing drive gas from the reservoir under development or one close by. It consists of three identical pressure vessels mounted in a tubular steel support. The vessels operate in three phases within this cycle: filling and separation, compression and transportation in which liquids are discharged into the oil export line, and decompression in which gas is discharged into a pipeline.

The Aker booster is designed to provide 10,000-40,000 b/d capacity for a 70-600 m water depth range and a transport distance of 25-70 km.

Aker is talking to a major producer about a joint development program. A feasibility study lasting 8-12 months may begin next year.

Both systems take an imaginative approach to a type of development that will become more common as the North Sea matures. It will be interesting to see which one wins the ultimate prize of purchase by producers.