EEMSHAVEN: Walk to work offshore Eemshaven

The port of Eemshaven, on the mouth of the Eems River estuary, is a vast area in the North East of the Netherlands with a huge potential for development. This potential has been recently recognised by Google who have chosen the area to invest hundreds of millions of Euros in building their new data storage facility.

One of the reasons for Google selecting this site was the ample production of renewable energy in the area and specifically from a new wind farm, Delfzijl Noord Wind Farm, being built nearby to be operated by Dutch utility Eneco. This onshore wind farm is described as being an onshore-offshore development, as it is being built on the Schermdijk dike, a spit of land with the channel leading to Delfzijl harbour on one side and the Eems River estuary on the other side. This location almost qualifies it for inclusion in this magazine in its own right.

The port already has a terminal for the HVDC NorNed submarine power cable connecting the Netherlands to Norway, an initiative of the European Market Coupling Company (EMCC) joint venture, made up of several TSOs, facilitating the exchange of electricity in North Western Europe. The new RWE power generation biomass plant being developed nearby in the port zone will also be connected locally to the Dutch grid. Eemshaven has also been selected for the site of the landfall of the two export cables, the onshore transformer station and grid connection of one of the largest offshore wind farm projects currently being built anywhere in the world, the Gemini windfarm, located 85kms north of the Netherlands. It was for this reason that Offshore WIND visited the port. The 600MW Gemini wind farm is the first one in the Dutch sector to be built outside the 12 miles coastal zone, qualifying it as an offshore wind farm in every definition of the term.

Gemini

The two Gemini export cables have to be run under 2 existing submarine cables, the interconnector NorNed and the telecommunication cable Tycom. For this reason two ducts had to be horizontally drilled at the cross-over location about 15kms North West of Eemshaven, between the German island of Borkum and the uninhabited Dutch island of Rottumeroog.

Due to strong currents and very shallow water depths at this location a very special vessel would be required to carry out the horizontal drilling operations for the two ducts separated by 25 metres. The EPC contractor responsible for the Gemini project is the Dutch family-owned marine business, Van Oord. In partnership with Fugro Seacore, this company also has a 50% share of a remarkable vessel, the jack-up barge WaveWalker 1.

WaveWalker 1

Built at the Neptune Shipyard in Hardinxveld-Giessendam, the Netherlands, the keel was laid on the 4th of April 2012, named on the 21st of September 2012 and by the end of the year it was working on the Van Oord contract in Brazil for which it had been designed.

This vessel is able to work in tidal zones where positioning by tugs or by laying anchors would be restricted or even impossible. The WaveWaker 1 is the ultimate ‘walk to work’ vessel and is fitted with 8 jack-up legs for this purpose.

On each of the 4 sides of the hull there is a frame with a jack-up leg mounted at each end. On the fore and aft sides of the hull the frames can be skidded to port and to starboard; and on the port and starboard sides the frames can skid fore and aft.

‘Walking’ is made possible with a 2-phase jacking and skidding sequence. In the first phase the hull is jacked up on the fore and aft legs and the port and starboard frames are skidded forward. The hull is then jacked up on these legs. In the second phase the fore and aft legs are retracted and the hull is skidded forward along the load-bearing port and starboard legs. The sequence is repeated, and so on, which, in perfect weather and seabed conditions, allows the vessel to reach a possible maximum speed of 40 metres per hour! A change in direction can be made in a ‘pixel pattern’ by skidding the hull along in the port or starboard directions.

The hull is constructed of 4 boxes creating a central moon pool which can be used for vertical drilling or seabed survey operations. The space within the hull contains the electrical switchboard, hydraulic jacking pumps and control, material, fuel and a small amount of food storage for the galley. Another speciality in the design

is the FSCL Gripper System instead of the usual ratchet and pin used for the jacking process. The walking process can be controlled by a ‘user friendly’ joystick system in the control room placed over the galley and mess room. Two cranes, a 100t Lagendijk LWC900 and a 10t Lagendijk LKB 13, are installed, one on each side. As the vessel is designed to be working in close coastal areas the accommodation on this location is limited to an office and galley/mess room. The crew members and drilling contractor personnel are currently ferried the 15km, 35 minute, journey to and from Eemshaven for their shift on board by a crew transfer vessel.

Horizontal drilling

This same boat was used when Offshore WIND visited the WaveWalker 1. We transferred from the vessel to a pontoon moored beside the WaveWalker 1 and were then lifted by the main crane on board using a Frog transfer capsule.

For the current operation the moon pool has been covered over and a unit has been installed for the horizontal drilling operation. The deck space is filled with all the associated equipment, the drilling machinery, drilling mud tanks and pipe racks, all fitted in container sized units. With an automatic drill pipe feeder lifting the drill pipe from the pipe rack and adding it to the drill string, the drilling operation is managed by one man and a remote control unit.

To change from drilling the east cable pipe to the west cable pipe the WaveWalker 1 is able to ‘walk’ the 25 metres and align the drilling equipment with pipe entry without using tugs or having had anchors laid previously. The operation will be completed early in 2015 with the exact timing dependant upon the weather conditions

The WaveWalker 1 is a versatile and unique vessel for work in conditions where other vessels would have great difficulty. This is a simple statement that covers a wide range of activities, conditions and properties, one of which is ‘walking to work’.

Dick Hill