THE DESIGN AND INSTALLATION OF EFFICIENT DEEP-WATER PERMANENT MOORINGS

Industry interest in floating production systems in the Gulf of Mexico and elsewhere is increasingly pointing toward deeper water depths ranging to 10 000 ft. In these waters, the moorings are an increasingly significant factor in the overall system cost. This paper presents important design considerations for deepwater mooring systems for permanently moored floating platforms. The engineering of feasible and cost-effective deepwater moorings requires substantive departures from conventional design and installation techniques. These include rethinking commonly accepted design criteria, the use of synthetic materials, alternatives to conventional catenary systems, increasing use of deeply submerged buoys, and innovative ideas for system installation. Issues addressed include: design criteria; the use of lightweight, high-strength materials such as aramid fiber rope in lieu of wire rope; analysis methods and procedures indicating the importance of quasi-static, dynamic, fatigue and probabilistic analyses; installation options and the benefits of maximizing deployment vessel options; the use of alternatives to a conventional chain/wire catenary system; and design considerations and construction options of large-buoyancy, deeply submerged buoys.