New high-strength synthetic ropes constructed of para-bonded aromatic polyamide (aramid) fiber are being developed for ultra-deepwater mooring applications. This paper highlights new laboratory tensile/fatigue testing of rope assembly, computer modeling analysis of mooring performance under operating conditions, and the potential economic impact.As the industry moves into ultra-deep water, traditional steel wire rope and chain moorings are being gradually displaced by polyester ropes. These synthetic ropes have been used in water depths between 3,000 feet and 8,000 feet. Questions arise, however, about whether polyester mooring ropes provide enough stiffness to maintain acceptable platform offsets in increasingly deeper water in all cases. Aramid fiber ropes are inherently stiffer and stronger than polyester ropes and therefore offer new solutions for ultra-deepwater mooring, as well as for other applications where production platform offsets may be critical.Advanced technologies are being developed to optimize aramid fiber performance and rope design configurations. New laboratory tensile and fatigue data are presented to demonstrate aramid fiber rope properties, performance capabilities, and minimum tension settings meeting API RP 2SM guidelines. Mooring analysis comparing the performance of an aramid mooring system with that of a polyester mooring system under simulated hurricane and loop current conditions shows significant reductions in platform offsets are achieved with the aramid system without compromising safety. This paper describes a new technology for ultra-deepwater mooring. The new approach offers the opportunity to design mooring systems for deeper water without modifying certain platform components and systems by incorporating stiffer, high-strength aramid fibers in the platform mooring system. Potential benefits include achieving optimal offsets for production risers in ultra-deep water, easier handling and installation due to smaller rope size, and greater flexibility in mooring system design. Economic analyses are presented to illustrate the advantages of the new technology as well as the financial impact.

The 1st Edition of API RP 2SM — Recommended Practice for Design, Manufacture, Installation and Maintenance of Synthetic Fiber Ropes for Offshore Mooring — was released in March 2001. Prior to then, most of the actual synthetic fiber rope mooring applications were installed in Brazil by Petrobras. Since the publication of RP 2SM, polyester moorings have been used in other deepwater basins, including the Gulf of Mexico, for both temporary drilling MODUs and permanent FPSs. Much has been learned from the actual design, manufacture, installation and operation of these systems by other operators and contractors throughout the past decade. This work has created an extensive knowledge base in the areas of both synthetic fiber rope behavior and mooring system design. To best capture these new learnings, an API Task Group assembled to perform a major update in developing a 2nd Edition. API RP 2SM is the recognized standard for synthetic fiber offshore moorings in the Gulf of Mexico as well as other deepwater basins of the world. It is used in conjunction with API RP 2SK (Design and Analysis of Stationkeeping Systems for Floating Structures, 2005) and API RP 2I (In-Service Inspection of Mooring Hardware for Floating Structures, 2008) for the design, manufacture, installation and maintenance of both temporary and permanent synthetic fiber mooring systems. This paper will present the key changes in the update of this API RP. Reasons for the changes and significance on a synthetic fiber offshore mooring project will be discussed. Major changes in the RP include sections on elongation and stiffness testing, contact with the seafloor, creep rupture and axial tension compression fatigue. The new guidance in the RP will allow for improved synthetic fiber mooring systems design, installation and operation while also potentially reducing cost. Introduction In 1997, Petrobras installed a 12-point taut leg polyester mooring system on its P-27 semisubmersible floating production system in the Campos Basin, offshore Brazil. This installation was a first in the offshore industry, and since then Petrobras has installed more than 20 polyester mooring systems on semis, FSOs and FPSOs. In 2004, BP was the first to install a polyester mooring system in the Gulf of Mexico (GoM) on its Mad Dog spar. Anadarko followed shortly by installing a polyester system on its Red Hawk cell spar. Since then several other projects (Gomez, Tahiti, Blind Faith, Independence Hub, Thunder Hawk, Mirage and Perdido) have used polyester mooring systems in the GoM. Polyster moorings are planned for future GoM projects, including Petrobras's Chinook and Cascade development. Additionally, polyester has been used for the Kikeh spar moorings in Malaysia as well as several CALM buoy moorings and turret moorings throughout the world. Similarly on the MODU side, in 2001 both Shell and BP successfully performed a full scale field trial of polyester mooring systems from a MODU. Since then, such systems have become more commonly used. In particular, after the 2004 and 2005 hurricanes, the use of polyester mooring on the MODUs has greatly increased as a possible means to mitigate overload failure or damage to infrastructure on the seafloor should a mooring system failure occur and the MODU go adrift during a hurricane.

The 1 st Edition of API RP 2SM -Recommended Practice for Design, Manufacture, Installation and Maintenance of Synthetic Fiber Ropes for Offshore Mooring -was released in March 2001. Prior to then, most of the actual synthetic fiber rope mooring applications were installed in Brazil by Petrobras. Since the publication of RP 2SM, polyester moorings have been used in other deepwater basins, including the Gulf of Mexico, for both temporary drilling MODUs and permanent FPSs. Much has been learned from the actual design, manufacture, installation and operation of these systems by other operators and contractors throughout the past decade. This work has created an extensive knowledge base in the areas of both synthetic fiber rope behavior and mooring system design. To best capture these new learnings, an API Task Group assembled to perform a major update in developing a 2 nd Edition.API RP 2SM is the recognized standard for synthetic fiber offshore moorings in the Gulf of Mexico as well as other deepwater basins of the world. It is used in conjunction with API RP 2SK (Design and Analysis of Stationkeeping Systems for Floating Structures, 2005) and API RP 2I (In-Service Inspection of Mooring Hardware for Floating Structures, 2008) for the design, manufacture, installation and maintenance of both temporary and permanent synthetic fiber mooring systems. This paper will present the key changes in the update of this API RP. Reasons for the changes and significance on a synthetic fiber offshore mooring project will be discussed. Major changes in the RP include sections on elongation and stiffness testing, contact with the seafloor, creep rupture and axial tension compression fatigue. The new guidance in the RP will allow for improved synthetic fiber mooring systems design, installation and operation while also potentially reducing cost. IntroductionIn 1997, Petrobras installed a 12-point taut leg polyester mooring system on its P-27 semisubmersible floating production system in the Campos Basin, offshore Brazil. This installation was a first in the offshore industry, and since then Petrobras has installed more than 20 polyester mooring systems on semis, FSOs and FPSOs. In 2004, BP was the first to install a polyester mooring system in the Gulf of Mexico (GoM) on its Mad Dog spar. Anadarko followed shortly by installing a polyester system on its Red Hawk cell spar. Since then several other projects (Gomez, Tahiti, Blind Faith, Independence Hub, Thunder Hawk, Mirage and Perdido) have used polyester mooring systems in the GoM. Polyster moorings are planned for future GoM projects, including Petrobras's Chinook and Cascade development. Additionally, polyester has been used for the Kikeh spar moorings in Malaysia as well as several CALM buoy moorings and turret moorings throughout the world.

New high-strength synthetic ropes constructed of para-bonded aromatic polyamide (aramid) fiber are being developed for ultra-deepwater mooring applications. This paper highlights new laboratory tensile/fatigue testing of rope assembly, computer modeling analysis of mooring performance under operating conditions, and the potential economic impact.As the industry moves into ultra-deep water, traditional steel wire rope and chain moorings are being gradually displaced by polyester ropes. These synthetic ropes have been used in water depths between 3,000 feet and 8,000 feet. Questions arise, however, about whether polyester mooring ropes provide enough stiffness to maintain acceptable platform offsets in increasingly deeper water in all cases. Aramid fiber ropes are inherently stiffer and stronger than polyester ropes and therefore offer new solutions for ultra-deepwater mooring, as well as for other applications where production platform offsets may be critical.Advanced technologies are being developed to optimize aramid fiber performance and rope design configurations. New laboratory tensile and fatigue data are presented to demonstrate aramid fiber rope properties, performance capabilities, and minimum tension settings meeting API RP 2SM guidelines. Mooring analysis comparing the performance of an aramid mooring system with that of a polyester mooring system under simulated hurricane and loop current conditions shows significant reductions in platform offsets are achieved with the aramid system without compromising safety. This paper describes a new technology for ultra-deepwater mooring. The new approach offers the opportunity to design mooring systems for deeper water without modifying certain platform components and systems by incorporating stiffer, high-strength aramid fibers in the platform mooring system. Potential benefits include achieving optimal offsets for production risers in ultra-deep water, easier handling and installation due to smaller rope size, and greater flexibility in mooring system design. Economic analyses are presented to illustrate the advantages of the new technology as well as the financial impact.

The MinDoc3 platform, a dry tree capable, spread-moored deep draft floater featuring three columns braced together, was selected for Mirage field development because of flexibility, functionality and ability to fabricate in the US Gulf Coast. This paper presents the MinDOC's global performance and discusses impacts from hull form, mooring design and riser interaction and makes comparisons to previous design standards. The Mirage Field is located in Mississippi Canyon 941/942 in 4000 ft WD. The weather criteria includes the impact of hurricanes Katrina/Rita, and allows for maximum wave heights and robust mooring considerations. The MinDOC's global performance has been modeled experimentally and numerically with good correlation. VIM behavior was determined experimentally, and suppression is achieved by only straking the interior portion of the upper columns, which simplifies horizontal construction. The MinDOC was chosen for its payload, robustness and low motions. The mooring system is a relatively typical 3x4 semi-taught chain-polyester-chain system with a radius of approximately 6700 ft. The MinDOC hull form global motions are sufficiently low to permit the use of Top-Tensioned risers and Dry Trees. The low motions reduce riser stroke, which also reduced tensioner stiffness, and reduce the coupling impacts on the global motions. The low motions were achieved by a conscious effort to concurrently design the hull, risers, tensioners and mooring systems. Introduction MinDOC hull design was initiated in late 2006 with design and fabrication commencing nearly in parallel. The initial design site is for the Mirage field, located in Mississippi Canyon in Blocks 941/942. The location is near the edge of the shelf and the mooring system water depth varies from 3,822 ft in the north, to 4,288 ft in the south. The mooring pattern consists of 12 lines arranged in three bundles spaced 120° with each bundle having four lines grouped in two pairs. The platform bow orientation is 156 degrees. The leg numbering starts with the SE most line, counting clockwise around. Each mooring leg is chain-polyester-chain and consists of 5" R4 studless top chain, 9.75" Polyester and 5" R4 studless bottom chains. The nominal radius is approximately 6700 ft from the fairlead to the anchor chain touchdown. The total nominal length of each line is 7,500 ft. (Figure 1).