The first use of TLP’s represents a very significant step in the advancement of floating platforms for the offshore petroleum industry. The basic concept for a TLP-type floating platform was being discussed in the early 1970s, driven by the perceived needs for such technology to produce the expected deep water developments. In 1973 Deep Oil Technology (DOT) formed a Joint Interest Project (JIP) funded by 12 companies. The JIP was basically the testing of a one-third scale model TLP offshore California and being successfully completed in 1975.
While most JIP participants did not show a great interest, Conoco, under the direction of L. B. Curtis and N.D. Birrell recognized the potential for the technology and continued studies within Conoco. This eventually led to the decision by Conoco to form an engineering group in the UK to design and install a TLP in the North Sea in Conoco’s Hutton Field. While the Hutton Field was in 147 meters of water, conventional type sea floor based structures could have been used. However, Conoco recognized the need for floating platforms for eventual deepwater production. The decision was made to develop the Hutton Field by developing the first major TLP. It was successfully installed in 1984 - approximately 14 years after first becoming interested in the concept. The Hutton TLP proved to be very successful and subsequently several other major TLP’s have been installed in the North Sea and the Gulf of Mexico.
Conoco continued their pioneering role in the offshore industry by putting a Tension Leg Wellhead Platform (TLWP) into service in 1989. The platform was located in the Jolliet field in the Gulf of Mexico operating at a waterdepth of 536 meters.
The Heidrun platform (1995) is the world's first concrete TLP and represents a significant step forward in deepwater production technology. The physical deck dimensions are massive: 150 x 80 m.
A new generation of TLP’s was designed by Atlantia Seastar. In 1998 the Morpeth platform was put into service, being the first single-column TLP (mini-TLP). This smaller design reduced the costs significantly by allowing a moderate amount of equipment.
A disadvantage of the single-column mini-TLP is that it is not stable without the tethers. The Typhoon TLP in the Gulf of Mexico capsized after a mooring failure. New variations (like a small spaced tri-column hull designed by ABB Lummus) will enable TLP’s to be stable without the tethers and maintaining the advantage of a small sized platform. Further advancements were made by moving the columns inboard and extending the legs of the structure. This latest type TLP is called an Extended Tension Leg Platform (ETLP).
In 2005 Conoco set another record by installing the worlds deepest TLP, the Magnolia, in a water depth of 1432 m. Initially Conoco planned to use composite materials for the tethers in order to reduce the own-weight and therefore coping with the increased loads, however due to regulations on an in-service inspection monitoring system they couldn’t comply with, Conoco was forced to use steel tethers instead.
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