New technology for anchoring

This article originates from the news archive of Det norske.

18. November 2010

Det norske and Viking Moorings has developed a new technology for safe storage of fiber rope on the seabed until mobilization of a rig.

Until now, only chain can be pre-laid. Fiber ropes are easily damaged. Damage can be caused by sand, corals and debris on the seabed. This has made it impossible to lay the fiber in advance. Det norske and Viking Moorings has now found a solution.

The solution was presented at the Anchor Handling Seminar in Stavanger last week. The main theme of the conference was reduction of manual handling, and less personnel exposure in dangerous situations.

Anchor handling vessel in the process of placing the bags with the fiber rope
Anchor handling vessel in the process of placing the bags with the fiber rope

For operators, the new technology, simplifies operations with pre-laid moorings. Mooring equipment can with this new technology be stored under water, improving efficiency and increasing flexibility in difficult anchoring operations. The technology requires no specialized tools or external cranes.To achieve sufficient elasticity in anchor moorings a combination of fiber rope and chains are used. Until now, only chain can be pre-laid.

Fiber ropes are easily damaged. Damage can be caused by sand, corals and debris on the seabed, a fiber rope is therefore considered damaged if it comes in contact with the seabed. This has made it impossible to lay the fiber in advance. Det norske and Viking Moorings has now found a solution.

Illustration "Fiber in a bag"

Illustration “Fiber in a bag”

With this new technology, you put the anchor out in advance, connect them to the fiber rope that is wrapped in a special way and stored in a “bag” on the seabed. In addition, a spin buoy can be used to lighten the connection with the fiber rope. When the rig is in place at the location, a vessel can “call on” the buoys using coded sound waves. The buoys will then rise to the surface. The vessels can then collect the buoys and at the end connect them with the rig’s chains.

This is summarized in the illustration above.

The technology with fiber rope in a bag, and similar solutions, is patent pending.Det norskes Bjørn Thore Ribesen and Arild Saasen together with Knut Ove Steinhovden, Steinar Ekrem and Espen Lea from Viking Moorings are the inventors. If the invention gets the patented, the patent will be owned by Viking Moorings. Det norske will get royalties for use. This is the first patent application for Det norske.

Anchor handling, especially in winter, can be time-consuming and therefore costly. The operations often have to wait for a suitable weather window. The probability to find a weather window to moor to a pre-laid anchor system is about 60 percent greater than the probability to find a weather window to anchor the rig as it arrives. Thus, this technology helps to reduce the cost of mooring and anchoring, and safety is improved. Anchor handling is one of the most dangerous operations during exploration drilling.

Read more about Viking Moorings on their website.

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About Det norske:
Det norske oljeselskap ASA has interests in a total of 72 licenses, with 35 operatorships. Det norske is the second-largest operating company on the Norwegian Continental Shelf both considering number of operatotships and exploration activity. I 2009 the company operated nine exploration wells, and the high activity will continue in 2010. Det norske runs its activities in a safe and responsible manner in close cooperation with the authorities.

Det norske currently employs a staff of 190. The company`s registered office is located in Trondheim. The company also has offices in Oslo, Harstad, and Stavanger. Det norske is listed on the Oslo Stock Exchange (DETNOR).