Deck installation is always a major challenge for floating structures, particularly deep draft floaters like the Spar which must be installed in relatively deep water. Derrick barges have been used for Spar deck installations until now. Murphy's Kikeh Spar, the 1st outside of the Gulf of Mexico, is the 1st Spar to use topside floatover installation technology and represents the 1st catamaran floatover installation of a topside onto a floating platform in open water. The successful execution of the Kikeh 4000Te topside floatover installation has established this method as a viable and cost effective alternative to lift installation.
This paper presents an overview of the topside floatover installation for the Murphy Kikeh Spar. The paper describes all aspects of the floatover installation including topside loadout and transportation using a single barge, transfer from the transportation barge to the catamaran barge configuration, catamaran open water tow and floatover to the Spar at the Kikeh location. This paper focuses on the naval architectural, structural and operational tasks that were performed in support of these operations.
New offshore developments may include several Spar type platforms with varying deck sizes ranging from 16,000 mt to 35,000 mt dry weights. Topsides for all previous Spar platforms were installed by deck lifts ranging from about 3,000 mt (Oryx single lift) to over 10,000 mt multiple lifts. The largest deck installed this way on a Spar was the Diana Deck with a dry weight of about 20,000 mt. This deck installation required five separate lifts . There are potentially large advantages, particularly for the large decks, if an integrated deck could be installed using floatover methods. Some advantages include:
Schedule and cost advantages for the integration and commissioning of modules on land rather than at sea,
Uncoupling the deck fabrication schedules from the availability of heavy lift vessels
There is a long history of successful floatover deck operations for floating Gravity Based Structures (GBS) and other floaters in protected waters ranging from the Beryl A Mobil facility in the UK North Sea, 1975, 14000mt deck weight to the Hibernia HMDC facility offshore Newfoundland Canada, 1997, 46000mt deck weight.
Until recently, however, only one (1) floatover has been performed on a floating structure in open waters which was the 24,000 ton Auger TLP Deck in 1993 . In 2006, the first floatover deck was installed on a Spar platform: the Kikeh Spar. This installation was performed in 1320 m water depths in the South China Sea, offshore East Malaysia. The deck weight was 4000 mt and the swell at the time of installation was Hs of 0.7m at periods of 7 - 8 seconds. This was also the first catamaran type floatover performed in open waters. The 46,000 mt Hibernia deck was set using a catamaran configuration in protected waters of Bull Arm in Newfoundland.
There are some significant differences between installing decks on a fixed platform versus a floating platform, and of course between sheltered and open water installations. Some of these differences are listed below.