Patent ID: 6851894

Claim:
A tension leg platform system, comprising: a tension leg platform operable to float in the sea; and a plurality of hollow and empty tethers for anchoring said floating tension leg platform to the sea bed, said tethers being operable to withstand a tension force to be generated between said tension leg platform and the sea bed, each of said tethers including an upper section having a positive buoyancy and including a lower section having a greater pressure resistance than said upper section, said upper section of each of said tethers having a larger diameter than said lower section of each of said tethers such that each of said tethers has a stepped reduction in diameter from said tension leg platform toward the sea bed, each of said tethers further including an intermediate section between said upper section and said lower section, said intermediate section having a wall thickness larger than a wall thickness of said upper section and smaller than a wall thickness of said lower section such that each of said tethers has at least two stepped increases in wall thickness from said tension leg platform toward the sea bed.