Subsea Success for NASNet05/05/2008
|Nautronix has completed the first field-wide deployment of NASNet by Subsea 7, in the Agbami field, offshore Nigeria. The field is operated by Star Deep Water Petroleum Limited (an affiliate of Chevron Corporation) on and is located approximately 70 kilometres offshore of the central area of the Niger Delta, Nigeria.|
The system, comprising of 14 NASNet sleds and 22 Mobile Transceivers (MTRx), was delivered to Subsea 7 in early July 2007, and subsequently mobilised to Subsea 7's umbilical lay and construction vessel MV Toisa Perseus, for operations on the Agbami field situated 350Km southeast of the city of Lagos. Subsea operations ranged from water depths of 1,280 to 1,650 msw.
On this project, the underwater acoustic positioning system provided total coverage for an area of approximately 50km2; this is believed to be the first time anyone in the world has achieved such wide field coverage with so few transponders.
The workscope was completed between September and December 2007 during which positioning was provided for:
- 6 Production manifolds
- 2 Gas Injection manifolds
- 4 Water Injection manifolds
After system mobilisation, the subsea stations were deployed by the Toisa Perseus on site in the Agbami field, with a network of 13 NASNet stations. The network was calibrated using a classic box-in method whereby the vessel navigated a circle around the station at a radius of approximately 0.7 x water depth.
Both work class ROVs on the Toisa Perseus (Hercules 3 and 4) were fitted with dual ROV receivers enabling rapid (typically 1 per second) position updates across the entire field in one complete referenced network.
The accurate installation of the suction piles and manifolds was achieved using NASNet MTRx systems which, as well as providing real-time position updates of the items throughout the water column, allowed the Subsea 7 and Nautronix survey teams to monitor pitch and roll via the internally integrated attitude sensors.
In order to monitor system performance, the location of three MTRx stations deployed across the field was regularly checked, especially during structure installations - the performance of the system throughout the operations met all expectations.
Further operational benefits of NASNet were highlighted when the scope of work was altered to accommodate drilling operations in the field. With the NASNet subsea reference network in place and covering the entire field, there was no need to redeploy in an alternative location saving considerable time on the project with minimal disruption.
The offshore phase of the operation onboard the Toisa Perseus was supported by Nautronix personnel throughout, both offshore and back in base. The Nautronix offshore crew developed an effective working relationship with the Subsea 7 vessel and survey team.
During the operations some issues were observed and many lessons have been learned, which will allow Nautronix to improve the system.
Read more about:
vessel ROV Offshore Positioning Construction
Supplier: Nautronix Group Ltd
More news from this supplier:
Nautronix Awarded Million Pound Contract by Ceona
Duo to Strengthen Nautronix' Senior Management
NASNet DPR Order for Nautronix
Nautronix Delivers First Systems of USD10m Order
Digital Acoustic Upgrades for Semi-submersible Drilling Rigs
NASDrill RS925 Positioning for Ultra-deepwater Drillships
Acoustic Positioning System for Ultra-Deepwater Drillship
Nautronix Wins Major Contract In Norway
Nautronix to Open New Office in Norway
Nautronix Expands Brazilian Activities
Shallow Survey 2015 Common Dataset Collection Has Begun
The Rocknes Casualty - A Chartmakerís Retrospect
OCTANS and PHINS to be Exported under Commercial Regulations
C-Nav Brasil Teams with Waypoint
2014 AUV Hydrographic Bootcamp
Ice Thickness Measurement from Space
Turbulence in Marine Environments Survey Successful
Closer Eye on Australian Waters
Optech at MAPPS 2014 Summer Conference
LINZ Formalises Antarctica NZ Relationship
comments powered by Disqus
Hydrography - More than nautical Charts
The Italian Navy has created a movie that gives a good insight into the various aspects of use of hydrography in addition to nautical charting. The movie has been made at the occasion of World Hydrography Day 2014.