In 1984 Conoco installed the first TLP, or tension leg platform, in the Hutton field in the British sector of the North Sea in 485 feet of water (see Figure 1). A TLP is a floating structure configured similar to a semi-submersible
, but with hollow tubular pipes called tendons that connect it to the sea floor. These tendons hold the platform in place but allow it to move hundreds of feet sideways. This flexibility allows the platform to ride with hurricanes or other large waves rather than resist them. Figure 2 shows a schematic of the TLP concept and Figure 3 shows a computer model that illustrates the hull (floating portion) and deck that supports the process and/or drilling equipment.
The concept was developed for deepwater applications where a traditional rigid structure would be too large and expensive. Although Hutton was not a deepwater platform, per se, it did prove the concept and led directly to Conoco's record breaking TLP, Jolliet, installed in 1760' of water in the US Gulf of Mexico in 1989. This was twice the depth of the deepest fixed platform. However, Conoco shifted focus from deepwater and was not able to follow-up on this success. Shell Oil took over leadership in deepwater with installation of a larger, deeper TLP in 1993. The Auger TLP was installed in 2800 feet of water in the Gulf of Mexico, nearly doubling the water depth record in one major step. Shell followed quickly with a series of TLP in increasingly deeper water depths.
This sustained series of developments by Shell, each with different oil company partners, gave the industry the confidence to aggressively pursue deepwater developments, both in the US Gulf of Mexico and around the world. Although not the first, many see Shell's accomplishments as the effective start of deepwater oil and gas development. Not only were these developments important technological advancess, deepwater has also added significantly to domestic oil production in the US, which had begun a steep decline as existing onshore fields rapidly depleted. Figure 4 illustrates the worldwide fleet of installed or sanctioned TLPs through 2003. The most recent, and largest, TLP in the world is the Shell Mars-B TLP, named Olympus, which was installed in 2013 and can be seen in Figure 5 with the original Mars-A TLP installed in 1995 in the background. The video from Shell shows the quayside installation of the production modules on Olympus and sail-away of the platform.