ABS is presently providing classification services for Murphy Oil's Medusa truss spar and for the Dominion/Williams Devils Tower truss spar, currently the world's deepest dry tree platform in progress. In general, spar systems are particularly suited to deepwater Gulf of Mexico applications by providing operators with increased flexibility in terms of water depth capability, extending traditional floating technology up to 10,000 feet of water.
Truss spars¡Xsimilar to caisson or classic spars in their operational profile¡Xare intended to offer some design improvement. The truss spar is primarily characterized by its space frame of tubular members, which provides the structural linkage between hard tank (flotation tank) and keel tank as well as support to the heave plates. The heave plates provide added mass and damping to further reduce heave motions and to improve stability. This arrangement is intended to save steel, allowing additional deck load, and providing required motion response performance.
ABS-classed as a A1 Floating Offshore Installation, the Medusa truss spar will be located on Mississippi Canyon Block 582 in 2,223 feet of water. Meeting the challenges of deepwater design and installation, the Devils Tower spar lighter in weight than the Medusa spar will employ different riser material because of its increased water depth location. Destined for deployment in 5,610 feet of water, the Devils Tower spar is operating on a very fast track, with the project scheduled to complete in 1.5 years.