Development of a Battered Four-Column TLP Concept

This paper discusses the development of the Atlantia’s new battered four-column TLP, called the FourStar™. As a result of battering the columns, the footprint of the new TLP is larger than a conventional vertical-column TLP, for a particular deck size. This results in several advantages, namely: • Increased stability, enabling quayside hull–topsides integration, wet tow of the TLP system, and self-supported tendon lock-off. • Better hydrodynamic behavior and smaller size tendons. • Improved pontoon access for SCR installation. The FourStar TLP consists of four columns of (rounded) rectangular cross-section, aligned along the diagonals of a square and battered towards the geometric center of the platform. The columns are connected by conventional rectangular pontoons, which aspect-ratio’s are optimized to improve the hydrodynamic performance. The basenode (column-pontoon connection) is structurally optimized for a ‘hot-spot-free’ stress distribution. Furthermore, the hull is designed for effective load transfer through the outer shell, which minimizes the steel weight. The tendon porches are located on the outer face of the base node, which maximizes their effective arm in the critical design case. The application of this concept to various payloads, including wet- and dry-tree production platforms, and various environmental conditions, including GOM, West Africa, and offshore Brazil is studied. The emphasize of this paper is on the hydrodynamic and structural aspects of the concept. Moreover, the results from an extensive series of recent wave basin model tests are discussed. Finally, the advantages of this new concept over a vertical column design are quantified for a typical GOM application, and its scalability is discussed.Copyright © 2007 by ASME