CHEVRON LAUNCHES STORAGE UNIT FOR ALBA FIELD IN U.K. NORTH SEA

Chevron U.K. Ltd. has launched a floating storage unit (FSU) destined for its Alba oil field development project in the North Sea.

The 125,000 dwt vessel, built in Astano SA's shipyard at Ferrol, Spain, can hold 825,000 bbl of crude oil.

The first FSU purpose-built for use in the U.K. North Sea, it will enable offshore loading of oil from Alba platform, due to be installed on Block 16/26 in June.

HOW IT WILL WORK

Designed to weathervane around a turret mooring system, the 800 ft long FSU will be secured by 12 anchor chains piled to the seabed. The mooring system is designed to allow continuous operation in waves as high as 15 ft.

A 12 in. pipeline will carry oil almost 2 miles from Alba field to the FSU, where it will be stored for loading at a maximum rate of 120,000 b/d into a 78,000 dwt shuttle tanker moored in tandem 250 ft away.

The pipeline from the platform will terminate at a subsea manifold, from which a 300 mm diameter flexible riser for stabilized crude will connect to the FSU turret. A 100 mm diameter flexible riser will be used to send diesel oil from the FSU to the platform.

Crude oil will be stored in the FSU's seven central tanks, while ballast water will be carried in wing tanks. Offloading will take place every 5-7 days, when cargo tanks are 60% full, during periods of maximum field production at 70,000 b/d.

If bad weather or shuttle tanker problems prevent offloading, ballast water will be discharged, creating storage for an extra 340,000 bbl of oil. If the FSU breaks away from its mooring, an azimuthing thruster in the stern will enable it to maneuver clear of the platform in a storm.

The FSU has accommodation for 58 people, although the normal crew will be 20. The accommodation block is designed to be the temporary safe refuge as required by U.K. safety rules arising from the Cullen Report of 1990 (OGJ, Dec. 14, 1992, p. 25).

RESERVES, PARTNERS

Alba field, with estimated reserves of 400 million bbl of oil, will be developed in two phases. The platform and FSU installation will deplete the northern portion of the reservoir, while the southern portion will be developed in 5 year's time.

Alba partners are operator Chevron 33.17%, Oryx U.K. Energy Co. 15.5%, Fina Petroleum Development Ltd. 12.65%, Santa Fe Exploration (U.K.) Ltd. 11.75%, Conoco (U.K.) Ltd. 9.33%, Union Oil Exploration Ltd./Baytrust Oil Explorations Ltd. 8%, Aran Energy Exploration Ltd. 5%, Conoco Petroleum (Alba) Ltd. 2.35%, and Amerada Hess Ltd. 2.25%.