Subsea rock installation is an important service that Van Oord has been supplying to the offshore industry for a long time. ‘We were at the cradle of the development of flexible fallpipe vessels and have been the market leader in the North Sea region for almost 30 years. Market opportunities grew, as did the scale of our operations. In the beginning, we could place 600 tonnes of stone every hour. Nowadays we do 1,800 tonnes an hour,’ says Koos van Oord, Offshore Subsea Rock Installation Manager. Want to read the whole story of a tale of a triumph? Read all about it in our magazine.
Van Oord holds the world record for the precise placement of rock in the deepest water, starting a new era of Subsea rock installation. The rock was installed at a depth of 1,277 metres. The rock installation operation was part of the development of the Asta Hansteen gas field and the Polared pipeline for the energy company Statoil.
How does it work?
A flexible fallpipe vessel installs rock on a sea or river bed using a fallpipe in order to protect or stabilise underwater structures or level the bed.
Advanced fleet of fallpipe vessels
Van Oord has three advanced flexible fallpipe vessels in its fleet. Nordnes, Stornes and the latest addition is Bravenes, a unique piece of equipment. The vessel, with a deadweight of 14,000 tonnes, a length of 154 metres, and a beam of 28 metres, is suitable for installing a wide range of rock sizes.
Bravenes is equipped to perform three different types of rock installation, namely the fallpipe through the moon pool, a fallpipe over the side, or a tremie pipe over the side. This third ship configuration allows the vessel to install rock very close to offshore platforms, such as monopiles. Bravenes brings a new level of innovation to subsea rock installation.
Cost-effective solution for seabed preparation
Van Oord has developed a technique for dredging at great water depths. This Deep Excavation System (DES) is an innovative method for preparing the seabed profile for installing offshore pipelines. The Deep Excavation System allows dredging to take place at depths varying from 100 to at least 1,000 m. Van Oord’s flexible fall pipe vessel Stornes can be equipped with this in-house developed system. It consists of the combined application of a sophisticated grab and a Fall Pipe Remotely Operated Vehicle (FPROV). The DES has a very accurate position control system and generates only very limited turbidity, which is vital in view of potential nearby sensitive marine environment like coral.
Here we offer leaflets with specifications for our featured equipment. Please feel free to contact us if you would like more information.