Judy Maksoud
International Editor

LISBON, Portugal -- A new four-column tension leg platform (TLP) developed by Atlantia Offshore Ltd. offers improved stability, enabling quayside hull-topsides integration, wet tow of the integrated TLP system, and installation without a heavy-lift vessel. Neil Williams presented the FourStar TLP concept at the International Offshore and Polar Engineering Conference on July 4.

The FourStar TLP consists of four columns of (rounded) rectangular cross-section, aligned along the diagonals of a square and battered toward the geometric center of the platform, Williams explained. The columns are connected by conventional rectangular pontoons, with an aspect ratio that is optimized to improve hydrodynamic performance. Williams presented the results of studies that evaluated performance under various payloads, including wet- and dry-tree production platforms and various operating environments, including the Gulf of Mexico, West Africa, and offshore Brazil.

The footprint of the battered column TLP is larger than a conventional vertical-column TLP, Williams said, and the larger keel footprint results in improved hydrodynamic behavior and smaller tendon requirements. The battered column gives improved pontoon access for SCR installation, he said. Atlantia is proposing the FourStar concept as an economical solution for deeper waters and larger payloads where the company's SeaStar is not a viable option.

According to Williams, the main advantages of the new concept are: