Page 74 - 4274

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 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. 2.28 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

74