Condeep

A Condeep under construction in Norway.

Condeep (abbr. concrete deep water structure) refers to a make of gravity base structure for oil platforms developed and fabricated by Norwegian Contractors in Stavanger, Norway.^[1][2][3] A Condeep usually consists of a base of concrete oil storage tanks from which one, three or four concrete shafts rise.^[4] The original Condeep always rests on the sea floor, and the shafts rise to about 30 meters above the sea level. The platform deck itself is not a part of the construction.

The Condeep is used for a series of production platforms introduced for crude oil and natural gas production in the North Sea and Norwegian continental shelf.^[1]

Following the success of the concrete oil storage tank on the Ekofisk field, Norwegian Contractors introduced the Condeep production platform concept in 1973.^[5]

This gravity base structure for platform was unique in that it was built from reinforced concrete instead of steel, which was the norm up to that point. The platform was purpose made for the heavy weather conditions and the great water depths found in the North Sea.^[1]

Troll A

Main article: Troll A platform

The Troll A platform is the largest Condeep to date.^[6] It was built over a period of four years, using a workforce of 2,000, and deployed in 1995 to produce gas from the enormous Troll oil field.

With a total height of 472 meters, Troll A was the largest structure ever to be built and moved. The total weight when launching was 1.2 million tons. 245,000 m³ of concrete and 100,000 tons of steel for reinforcement were used.^[7] The amount of steel corresponds to 15 Eiffel towers.^[7] The platform is placed at a depth of 300 meters. For stability, it is dug 35 meters into the sea floor.

North Sea concrete platforms

Structure	Depth	Operator and year
The Ekofisk-tank	70 m	Phillips, 1973
Frigg CDP1	104 m	Total, 1975
Beryl A Condeep	120 m	Mobil, 1975
Brent B Condeep	140 m	Shell, 1975
Brent D Condeep	140 m	Shell, 1976
Frigg TCP2 Condeep	104 m	Elf, 1977
Statfjord A Condeep	146 m	Mobil, 1977
Statfjord B Condeep	146 m	Mobil, 1981
Statfjord C Condeep	146 m	Mobil, 1984
Gullfaks A Condeep	135 m	Statoil, 1986
Gullfaks B Condeep	142 m	Statoil, 1987
Oseberg A Condeep	109 m	Norsk Hydro, 1988
Gullfaks C Condeep	216 m	Statoil, 1989
Draugen Condeep	251 m	Shell, 1993
Sleipner A Condeep	82 m	Statoil*
Troll Condeep	303 m	Norske Shell, 1995
Heidrun TLP	350 m	Conoco, 1995

^{[8] [9]}

• The original concrete structure of Sleipner A sunk during trials in the Gandsfjord on August 23, 1991. A new structure was built, and deployed in 1993.

Sources

• Fagerberg, Jan; Mowery, David C.; Verspagen, Bart (2009). Innovation, Path Dependency, and Policy: The Norwegian Case. Oxford University Press US. ISBN 9-7801-9955-1552. 
• Nawy, Edward G. (2008). Concrete construction engineering handbook. CRC Press. ISBN 9-7808-4937-4920. 
• Mehta, Povindar K. (1990). Concrete in the marine environment. Taylor & Francis. ISBN 9-7818-5166-6225. 
• Gerwick, Ben C. (2007). Construction of marine and offshore structures. CRC Press. ISBN 9-7808-4933-0520. 
• Arentsen, Maarten J.; Künneke, Rolf W. (2003). National reforms in European gas. Gulf Professional Publishing. ISBN 9-7800-8043-6876. 

References

1. ^ ^{a b c} Fagerberg; Mowery; Verspagen, p.192
2. ^ Mehta, Povindar K. p.4
3. ^ Gerwick, Ben C. p.166
4. ^ Dr. techn. Olav Olsen, Condeep platforms, (in Norwegian) 2011, web page by Norwegian Petroleum Directorate, retrieved 2011-08-30
5. ^ Arentsen; Künneke p. 90
6. ^ Fagerberg; Mowery; Verspagen, p.191
7. ^ ^{a b} "Guinness World Records - largest offshore gas platform". Guinness World Records. 1996. http://www.guinnessworldrecords.com/records/science_and_technology/buildings/largest_offshore_gas_platform.aspx. 
8. ^ Nawy, Edward G. Chapter 13.7
9. ^ Gerwick, Ben C. p.515