Aberdeen company Nautronix has just delivered a NASNet acoustic positioning package to Wick in preparation for a pipeline bundle tow-out from Subsea 7’s fabrication yard.
This will be the first time that NASNet has been utilised for this type of application; it is more usually associated with deepwater field developments. The package will provide positioning and depth information of the towhead, trailhead and three positions on the 2.9km bundle relative to the support vessel, the tow vessel and the trail vessel. Internal carrier pressure information from the bundle will also be provided.
For this operation, Nautronix carried out a number of modifications to the technology, which the company has always seen as being capable of a variety of applications.
Engineering manager Stewart Duncan said: “The usual mode of operation for NASNet is to deploy stations on the seabed in a network and use these to give position reference signals to position equipment within the water column.
“For this project, we are reversing this principle and tracking the position of the beacons on the bundle using the position of the vessel and numerous constraints, meaning we have one reference point providing full positioning rather than a network. It is an exciting opportunity for us to use our technology in another way.”
This is the second time Subsea 7 has used the Nautronix system in recent months. Late last year, the company reported the successful completion of the first field-wide deployment of NASNet by this subsea contracting major.
Deployment was in Chevron’s Agbami field development offshore Nigeria and the system comprised 14 sleds and 22 mobile transceivers. On this project, the underwater acoustic positioning system provided total coverage for an area of about 50sq km. Nautronix claims this may be the first time anyone in the world has achieved such wide field coverage with so few transponders.
In Brazil, Nautronix has just completed a deployment of its positioning system with Acergy on the deepwater Frade field operated by Petrobras.
An extensive array of equipment was sent from Aberdeen to the construction vessel, Normand Mermaid, which was lying in Dusavik, Norway, prior to its voyage to Brazil in early-January, 2008.
The Nautronix team provided offshore personnel to assist Acergy with the deployment and calibration of the network, which was successfully completed during early-February – well within the scheduled timeframe, saving valuable vessel time.
Following the Normand Mermaid deployment, the NASNet surface equipment is being transferred on to another vessel, Polar Queen, which is to continue work in the Frade field.
This is expected to be undertaken through 2008 and beyond.