The use of HMPE mooring lines in deepwater MODU mooring systems

The use of synthetic components, particularly polyester, in deepwater Mobile Offshore Drilling Units (MODUs) mooring systems has become a viable option to extend the mooring capabilities of a MODU. To date, the use of synthetic components in MODU moorings has mostly been limited to polyester, with few exceptions. This paper will focus on an alternative synthetic mooring component, High Modulus Polyethylene (HMPE), for use in deepwater MODU mooring systems. This report highlights key aspects of MODU mooring system performance when analyzed with HMPE components. As a benchmark, the performance of other systems including conventional catenary mooring systems and polyester mooring systems are compared with the performance of HMPE mooring systems. The mooring systems considered in this study range in water depths up to a maximum of 10,000-feet. MODU and mooring system responses were analyzed for the survival condition or draft with Gulf of Mexico (GOM) hurricane metocean conditions. The limiting line tension utilization and FOS (Factor of Safety) values from the survival analyses are compared for all mooring system types showing the range of survivability/performance between the different mooring systems. Also shown are MODU passive offsets among the different mooring systems analyzed. Conclusions from this study will show that an HMPE MODU mooring system can be engineered to have similar performance as a polyester system in deepwater applications, including survivability and station keeping ability.