From Australia (RW): Woodside Petroleum plans to deploy three floating LNG units to produce from 64 subsea wells to develop the Browse Basin (SEN, 30/13) gas fields off Western Australia.

Overall contingent reserves for the development are 450 bcm and 436 mmbbls of condensate. The project is expected to have an operational lifetime of 50 years.

Details of the planned development have emerged in the Browse FLNG Development Environment Protection and Biodiversity Conservation Referral document submitted to the federal government.

Lots of drilling
The development which includes the Torosa-Brecknock-Calliance gas/condensate fields about 290km off the Kimberley coast, will incorporate five drill centres at the Torosa reservoir and three each at Brecknock and Calliance. Subsea infrastructure will include a dozen manifolds plus flowlines, umbilicals and moorings.

Of the three FLNG facilities, one may be moved between the Torosa and Brecknock/Calliance reservoirs. It is likely there will be two facilities located at Brecknock/Calliance for about half the fields’ life and two facilities at Torosa for half that field’s life.

The use of FLNG technology will limit the project’s footprint to 67ha.

The major challenge in an already complex plan is that much of the Torosa reservoir lies beneath Scott Reef. The reservoir is also compartmentalized and will require drilling from a number of locations to enable optimum recovery. Production wells will be drilled to depths of 3,500 m to 4,500 m below sea level. Some horizontal drilling will be needed.

Infield flowlines are likely to be flexibles or carbon steel internally lined with corrosion-resistant alloy.

The FLNG design is expected to be similar to that at Shell’s Prelude (30/18) project with each vessel producing about 4mt/a of LNG along with up to 22,000b/d of condensate.

The FLNG facilities will each have eight storage tanks with capacities of 266,000m3. Boil-off gases generated during LNG storage and offloading will be compressed for re-use in the fuel gas systems.

The vessels will be turret-moored enabling the facilities to weathervane into the prevailing wind. Mooring lines will be secured with suction or attached to driven or gravity-based piles, each of which will be 6- 8m dia and 30m long weighing 180t.

The project is expected to go into FEED stage next year with a final investment decision to be made in 2015.