Horizontal Installation of TLP Tendons

Tension Leg Platforms (TLPs) are ideal supports for dry-tree top tension riser systems because their tendons exhibit high tensile stiffness and significantly reduce the heave, pitch, and roll motions of the platforms. Since the first TLP (Hutton) was installed in the North Sea in 1984, a total of 24 TLPs have been installed throughout the world with 16 of them installed in the Gulf of Mexico. Currently there are new TLP projects proposed in regions off the coast of Malaysia, West Africa, Brazil and Western Australia. Heavy-lift vessels were used to install tendons for most of these TLP’s. Tendon joints were assembled vertically from bottom part to top part. Using a heavy-lift vessel introduces significant cost and schedule challenge to TLP projects, especially ones located in remote regions. A horizontal tendon installation methodology is presented in this paper. This innovative approach involves horizontal assembly of TLP tendon segments on a construction barge. The partially assembled tendon is then incrementally pulled out through a stinger at the barge stern and secured with a hold back clamp so that the next tendon joint can be connected. The process repeats itself until the whole tendon is assembled and deployed. The tendon is then upended to a vertical configuration and connected to a TLP or a foundation pile. In this paper, we examine the alternative equipment and configuration options in the horizontal installation methodology. We outline rationales to select the appropriate options and measures to reduce project cost and risks.