The precise positioning of the topside and gravity based structure nearshore was performed successfully for ExxonMobil, made possible with the application of Fugro’s Starfix Suite accurate positioning software which minimised project risk.
The seabed scan of the towing route and real-time positioning for the supportive ten towing vessels, nine anchor barges, one ROV support vessel and ultimately the centimetre level positioning of the mated Hebron Platform on site resulted in a realised project schedule for ExxonMobil in strong partnership with Fugro.
Hebron is a heavy oil field and is estimated to produce more than 700 million barrels of recoverable resources. The field was first discovered in 1980, and is located offshore Newfoundland and Labrador (NL) Canada in the Jeanne d'Arc Basin. The field is being developed using a stand-alone concrete gravity based structure (GBS). The GBS is a vast reinforced concrete structure designed to store up to 1.2 million barrels of crude oil while withstanding sea ice, icebergs and the extreme weather conditions anticipated during its operational life. It supports an integrated Topsides deck that features living quarters and facilities needed to perform drilling and production duties.
The Hebron platform weighs in at 750,000 Tonnes and was manoeuvred 367nm through an area known as ‘iceberg alley’.
Fugro were contracted by Kiewit-Kvaerner Contractors (KKC) on behalf of ExxonMobil to provide a range of services associated with mating the GBS and the Topsides and moving the rig into position.
In preparation for the rig move, a multibeam echosounder (MBES) survey of the intended tow route from the deepwater site at Bull Arm, Trinity Bay to the Hebron field (367 nautical miles), was undertaken to minimise risks of grounding. Next, shore based terrestrial and DGNSS positioning services were provided for the mating of the topsides and the GBS, that together make up the Hebron platform, were provided. The use of pinpoint precision and reliable Starfix.NG software was critical to the success achieved by Fugro on this project.
With the assembled structure ready to be moved, positioning services for the platform and tow vessels required to transport and position the completed platform on site (21 individual vessels at once) were supplied.
Additional positioning services for the ROV support vessel and full ROV multibeam perimeter survey post set down were also provided. Fugro supplied two streams of real-time ROV video transmitted from the ROV support vessel to the platform and a VOIP telephone system between the Platform, and three tow/support vessels to enable reliable, private voice communications between Fugro staff. Real-time video displaying the tension monitors on four of the tow vessels was provided, as was precise motion monitoring of the Platform while under tow and during set down.
The client was provided with final legal plan of survey of the installed platform and all well bays, upon completion of the 367 nautical mile tow of the 750,000 tonne structure which was installed to less than 1m and 0.1° of the proposed set down location.