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risers), instead of on the seafloor . This makes for a cheaper well completion and

gives better control over the production from the oil or gas reservoir. The first

Tension Leg Platform was built for Conoco's Hutton field in the North Sea in the

early 1980s. The hull was built in the dry-dock at Highland Fabricator's Nigg yard

in the north of Scotland, with the deck section built nearby at McDermott's yard at

Ardersier. The two parts were mated in the Moray Firth in 1984. Tension Leg
Platforms (TLPs) are floating facilities that are tied down to the seabed by vertical

steel tubes called tethers. This characteristic makes the structure very rigid in the
vertical direction and very flexible in the horizontal plane. The vertical rigidity

helps to tie in wells for production, while, the horizontal compliance makes the
platform insensitive to the primary effect of waves. It has large columns and

Pontoons and a fairly deep draught.

The Tension Leg Platform (TLP) consists of a floating structure (semi-

submersible) with excess buoyancy which is restrained by tautly moored vertical or

inclined cables (tension legs). The cable network limits platform motions and

provides restoring force to maintain position. The economical applicability of the

tension 1eg platform concept begins at locations where conventional platforms

cannot be used.

Although still in the preliminary stages, the tension-leg platform (TLP)

concept appears a viable means of affording offshore oil and gas production while

remaining relatively economically insensitive to water depth. In many cases, the

TLP offers distinct cost advantages over fixed-platform installations, yet it retains

many of the platforms' desirable operational characteristics, such as stability,

ability to use land-type drilling equipment, and larger overall production capacity

than floating facilities.

The offshore industry has been interested in the tension-leg platform for

several years. Research firms, manufacturers, users and potential users, and any

number of professional organizations and universities have participated in

exploring various theories and ideas for TLP drilling, production, and mooring

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