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capacity C-link connectors were the water deballast system pumped procured and used to connect water out of the provisional ballast tanks. work chain segments to top Submersible pumps and deballast hoses chains and additional analy- were preinstalled into provisional ballast sis proved that the hull could tanks, and a generator was transferred sustain a 10-year return storm to the top of the hull after the topsides with or without topsides. Tugs were removed to power the pumps. After

Gulf of Mexico were hooked up to provide sta- mooring lines were disconnected and tion keeping while the mooring temporarily laid on the seabed, com- disconnect was completed. pressed air was then pumped into the variable ballast tanks from the DB50 to

Ballasting and deballasting raise the hull to the 400ft draft. Since

Limited access to the spar the windlass and work chain were no during key activities required longer available, the DB50 assisted in the a remote ballast/deballast mooring disconnect by lowering each system for all operations. The top chain through the chain stopper with variable ballast control system its crane. Once the Kirt Chouest hooked was located on the topsides. into the top chain below the surface, an

The connections between the

ROV cut a sacrifcial sling and the AHTS hull and topsides had to be vessel laid each line on the bottom for removed prior to topsides lift. recovery after the hull was towed from

The spar hull was 560ft long, the feld.

64ft in diameter and assembled

Towing and reefng with six outer cells connected

The 70mi tow route from Garden Banks to the center cell. There were 876 to Eugene Island 384 was laid out to void tanks on top of each cell minimize pipeline crossings, maximize with variable ballast tanks the hull’s distance from other platforms, under them. Each had an air- and maintain adequate bottom depth over-water system that was clearances during the fnal approach to open to the sea at the bottom.

Pumping air pushed water out and reduced the draft, while venting air would let more water in to lower the spar. The hull frst needed to be ballasted low enough for Versabar’s heavy lift vessel VB10000 to hook up and lift the topsides.

After that, the hull needed to be deballasted to reach a tow draft of 400ft to enable the spar to enter the 430ft deep reefng site. To facilitate the required draft variations, InterMoor set up three different systems on

DB50 and the spar: an air bal-

Topsides being lifted of towing.

last/deballast system, a water

Derrick Barge 50 (DB50), while Edison Mooring disconnect ballast system and a water deballasting

The mooring system on Red Hawk had

Chouest Offshore’s AHV Kirt Chouest was system. only one windlass and one 800ft long Pumps, compressors and manifolds used for mooring disconnect and mooring work chain located on the topsides to were staged on the DB50 and connected recovery. InterMoor has not only sup-

INTELLIGENT TANK MANAGEMENT service all six mooring legs. To reduce to the tanks in the spar hull through ported multiple projects for Anadarko

Scanjet is a leading global supplier of tank cleaning equipment the loads during mooring disconnect water and air hoses. Ballasting contin- prior to Red Hawk, but also was involved, and solutions for any marine and ofshore application. Scanjet at the time as a division of Technip, in the the work chain had to be removed prior ued during the four-hour topsides lift designs and produces a range of fxed and portable tank clean- ing equipment, marine protection systems, high level overfll installation of Red Hawk. Todd Veselis, to the topsides lift. The work chain was operation to maintain the draft as the alarms, vapour emission control systems, tank level gauging general manager of Permanent Moorings cut in three pieces and paid out on three weight was gradually taken by VB10000. equipment and Scanvent P/V valves. for InterMoor, said that engineering manu- mooring legs, thus effectively lowering The lift required very calm seas as this als from Red Hawk installation were still the tension in the entire mooring system. was VB10000’s frst topsides lift from a shelved in his Houston offce when the

At that point the system was slacked to foating platform. Therefore, the motions

Phone: +46 31 338 7530 decommissioning engineering started. facilitate topsides removal. However, the of the two bodies had to be adequately

E-mail: [email protected] www.scanjet.se

That knowledge and experience was cer- platform still needed to remain storm managed. Free of its topsides, the hull tainly benefcial to the project.

safe throughout the topsides lift. High was then deballasted in two stages. First,

May 2015 | OE oedigital.com 114 112_OE0515_Geo3_InterMoor.indd 114 4/20/15 10:02 PM