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systems. Some having gone as far as designing and testing prototype equipment.

System, environment, and platform geometry have been treated specifically to

develop a cost-efficient extension of existing technology. Very soon, the world's

first TLP will lie securely fixed in 485 ft of water in the North Sea.

By iterative process, a design was selected by Vetco Offshore Inc. as a

practical approach to TLP drilling. Detail design and testing of products followed.
The result, described here, and depicted in fig. 6.37 represents current TLP drilling

technology and promotes the advancement of the TLP concept in the quest for
offshore energy sources.

SYSTEM DESCRIPTION
The unique design of this TLP permits the use of land equipment and

modified conventional platform methods, thus allowing simultaneous drilling and

production to be safely conducted. The tethers that tie the platform to mooring

templates on the ocean floor are kept in tension through the worst weather and

demanding deck loading conditions by the buoyancy of the platform's integral

columns and pontoons. Deck designs and well arrangement optimize platform

space utilization. Use of a high-pressure drilling riser permits blowout preventers

(BOPs) to be located in the drilling rig substructure for easier, more reliable

installation, operation, and maintenance. Drilling, completion, and production are

accomplished without large conductors from sub- sea wellhead to platform,

minimizing weight and reducing stress. The high- pressure drilling riser

connectors, modified to accept AX seal gaskets, ensure sealing integrity

comparable to hydraulic connectors which attach BOPs to subsea wellheads.

The TLP drilling system consists of a subsea wellhead to which the high-

pressure drilling riser is attached; a tapered transition section just above the sea

floor to minimize stress and increase fatigue life; drilling riser joints; and a

gimballed tensioning system for support. Upon completion, each well will be tied

back to the platform for control at deck level. Key components are simple and

inherently reliable but will have redundant backups and are replaceable for

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