Low-Draft, Low-Motion, and Cost-Effective SCR-Compatible Semi-Submersible Hull for the Central GOM

Abstract A semi-submersible hull (patent pending) with simple geometry, low draft, low motion, and low cost has been developed for use with simple SCRs in the central Gulf of Mexico (GOM). Simple SCRs, known for their cost-effectiveness and proven performance in deepwater, are widely considered for deepwater operations. However, they require a host platform that offers low heave motions, especially in central GOM environments. To meet this requirement, the hull design ensures that the heave motion RAOs for periods between 10 and 18 seconds remain below 0.33 m/m, minimizing vertical motion under wave conditions, while the heave natural period exceeds 22.0 seconds to ensure stable dynamic responses to wave action. The design features a low draft (less than 30m) and simple geometry, increasing potential competition. Emphasizing SCR compatibility and ease of fabrication, transport, integration, and installation, it offers a cost-effective solution for deepwater operations. The hull’s performance has been preliminarily assessed through two case studies: one supporting a small topsides payload of 11,000 mt at 1,500 m depth, and another supporting a medium payload of 25,000 mt at 2,500 m depth. Draft-sensitive studies are also presented, addressing various heave motion amplitude requirements from 0.30 m/m to 0.40 m/m.