NKK Super Semi-Submersible Rig Designed For D e e p Sea O p e r a t i o ns

Nippon Kokan (NKK), Tokyo, has developed a super semi-submersible drilling rig specially designed for oil and natural gas drilling operations in deep water and rough seas. The rig features a computer-controlled dynamic system to maintain position in deepwater operation in depths to 1,600 meters (about 5,250 feetl. The system employs eight sets of 4,200-hp azimuth type thrusters.

The new rig can maintain optimum operating conditions with favorable motion characteristics, as well as withstand 110-knot winds, 18-meter (59-foot) waves, and threeknot currents.

The deck of the super semi is about 272 feet long with a beam of 231 feet. Pontoons are 3671/- feet long, 50 feet wide, with a height of 37 feet; they are spaced 190 feet center to center. Operating draft is 90.22 feet and survival draft is 78.74 feet.

"This super semi has a higher payload of more than 13,000 tons in transit and a deck load of 5,300 tons under operation conditions," said Minoru Hashimoto, president of NKK America Inc., NKK's U.S. subsidiary. "And because of the rig's high variable deck load capacity and larger storage space, it is well suited for production use as well," he stated.

For winter operation, the rig has a special cover for the upper operating deck to shelter workers from low temperatures. Also, to minimize icing effects, there is less vertical bracing used in the structure.

The super rig's design is based on an NKK/Trosvik Bingo-4000 design. A series of performance tests, such as wind tunnel and sea keeping using scale models was completed at NKK's Tsu Facilities.

The rig also meets the latest worldwide regulations for mobile offshore drilling units, including the Norwegian Maritime Directorate, Det norske Veritas, American Bureau of Shipping, U.S. Coast Guard and Department of Energy.

By developing this and the Norwegian Yatzy type mini-size semisubmersibles, NKK now has the capability to build three different types of semi rigs—mini, large, and super sizes—to meet the wide range of requirements of the world's offshore drilling industry.

Maritime Reporter Magazine, page 10,  Apr 1984 Basil Peters

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