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Engineering feat of the month: Draugen platform

Posted by: Gary Chapman

Discovered in 1984, Draugen is a well-known oil field and the first field developed in the Norwegian sea. The field, situated 93 miles off the coast of Norway operates at a sea depth of 250m and is operated by Shell who hold 26.20% ownership. The remaining ownership is shared out between Petoro, BP and Chevron.
The platform itself is unusual in its appearance and has become an iconic structure amongst oil workers. It is the only Condeep (concrete deep water) structure built with a single shaft – known as a monotower. A Condeep is a gravity-based structure where the concrete base resting on the sea floor acts as a storage tank for the stabilized oil. The oil is deposited into tanks at the base of the facility and is connected to two large pipelines that transport the oil to the floating loading buoy. The concrete structure made so iconic by Draugen is designed for severe weather conditions and deep waters such as those found in the North Sea.

Source: Wikipedia

Draugen began producing oil in the field in 1993 and since then, use of 4D seismic technology has helped Shell increase the estimated production life of the Draugen field. Production is expected to continue until at least 2037 thanks to several investments made to extend its life. The field originally had an estimated life of between 17-20 years and a predicted recovery rate of under 40%.
In its peak, Draugen’s output was 225,000 b/d of oil, which more than exceeded the planned average production of 90,000 b/d. The associated gas from the operation is transported to Kårstø through the Draugen gas export pipeline which ties into the Asgard Transport system.
There are two homogeneous reservoirs from which the Draugen field produces oil. The main reservoir containing sandstone of Rogn formation is from the late Jurassic age. The second is the Garn formation found to be of middle Jurassic age and both reservoirs lie at a depth of 1,650m.

Draugen is made up of a total of 11 wells, five subsea wells connected to the main Draugen facility and six subsea water injection wells. Most recently, the Norwegian offshore safety watchdog - the Petroleum Safety Authority - have approved Shell’s request to drill a further two subsea wells.
Recently an additional living quarter was added to the platform which allowed the accommodation capacity to increase by 60% which allowed upgrading projects to proceed. These developments will only add to the longevity of operations at the oil field.
The Draugen platform is a real iconic feat of offshore engineering. Here you can see how the design compares to other well-known concrete sub structures.
Source: Kvaerner

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