The Terra Nova FPSO consists of a new-build vessel with a disconnectable internal turret mooring system. Nineteen risers and umbilicals from four drill centers are connected to the turret with a maximum design throughput of 150,000 bopd. The turret system is designed to allow the vessel to quickly disconnect from its moorings and risers to avoid impact with unacceptably large icebergs, and to allow the FPSO to remain moored on station during the severe 100-year storm conditions. These unique requirements for Terra Nova have resulted in the development of one of the most sophisticated turret mooring systems to date. This paper presents some of the key drivers that led to the unique design of the Terra Nova turret mooring system, and provides a detailed description of the various components of the turret, focusing on both the structural and mechanical, and the fluid-transfer systems. The paper also provides an overview of the disconnection and reconnection of the turret mooring system, illustrating its compliance with the stringent requirements in the design basis. Finally the paper provides a summary of the turret design, fabrication and installation milestones over the life of the project. Introduction The Terra Nova FPSO will be located in approximately 95 meters water depth on the Grand Banks off the East Coast of Newfoundland, Canada. The harsh environment at the Terra Nova location is much like the northern North Sea with a 100- year significant wave height of 16 meters, and 1-hour mean wind speeds of 40 m/s. The FPSO is situated in "iceberg alley" where large icebergs from Greenland and Ellesmore Island drift south with the Labrador current. Surveys have shown the presence of iceberg scour marks on the seabed, and statistics indicate that the site could see as many as 66 large icebergs in a single season (April - July). Table 1 provides a summary of the design storm conditions for both the 1-year and 100-year return intervals. The Terra Nova FPSO system consists of a new-build FPSO vessel with a disconnectable internal turret mooring system. The turret supports 14 risers and 5 umbilicals servicing wellheads in four or more glory holes, with a maximum design throughput of 150,000 bopd. The turret mooring system has been designed to maintain station in the 100-year storm environment, and to be disconnectable to avoid an approaching iceberg on a collision course. Once the FPSO disconnects, the mooring and riser system is supported by the spider buoy that has an equilibrium depth of 35 meters below sea level. This paper provides a detailed description of the unique turret mooring system designed by FMC SOFEC Floating Systems for the Terra Nova FPSO, focusing on both the structural and mechanical system, and the fluid-transfer system. The paper also provides a description of the disconnection and reconnection of the turret mooring system, and the design, fabrication and installation milestones over the life of the project.
In the past 10 years developments in technology and the opening up of new frontiers, combined with a demand to move into greater water depths have resulted in considerable increase in the use of floating facilities for offshore oil production. The Terra Nova Development has and will establish a number of project "firsts" including the first FPSO to operate in North American waters and the first to operate in a harsh North Atlantic environment frequented by sea ice and icebergs. Also stereotypical of this region are cold air and water temperatures, seasonal fog, and heavy seas. Overcoming these challenges has required Terra Nova to adopt the lessons learned from pervious FPSO developments in the North Sea, while using both proven and new technology, and utilizing the benefits on an alliance-based contracting approach. The result is a unique development solution with a number of lessons learned. Introduction The Terra Nova oilfield is located approximately 350km (220 miles) east-southeast of St. John's, Newfoundland, 35km (22 miles) southeast of the Hibernia oilfield in a water depth of 90 to 100m (295-330ft.). Figure 1 shows the field location. The total recoverable oil reserves in the field are estimated by the Canada-Newfoundland Offshore Petroleum Board (CNOPB) to be some 64?106m3 (400 million barrels). The top of the reservoir is located 3,200m (10,500ft.) below the seafloor. The field is made up of three geological fault blocks: the Graben, the East Flank and Far East as shown in Figure 2. Only the Graben and East Flank blocks have been delineated. Twenty-four wells are proposed for Graben and East Flank: 14 producers, 7 water injection and 3 gas injectors. If further delineation drilling in the Far East block, which is planned for 2002, locates commercially viable hydrocarbon reserves, an additional 5 producers and 5 water injectors may be required. The Terra Nova field development concept is shown in Figure 3. An ice strengthened, double-hulled Floating Production, Storage and Offloading (FPSO) facility with subsea wells and gathering system will be used for the development of the Terra Nova field. Development wells are being drilled using the mobile semisubmersible drilling unit "Henry Goodrich," through seven subsea templates placed in four 10m deep glory holes, used to protect the wellheads and xmas trees from scouring icebergs. Trenched and rock bermed flowlines connected to flexible risers will link the subsea wells to the FPSO. Crude will be offloaded by a dynamically-positioned shuttle tanker positioned at the stern of the FPSO. Terra Nova - A Project of Firsts The Terra Nova Development has set a large number of "firsts" which have significantly contributed to the challenges in the execution of the project. These "firsts" are varied in theme and include:First FPSO development on the Grand Banks and only the second offshore oil development on the challenging Grand Banks of Newfoundland.First offshore facility in Canada to be certified to both offshore petroleum and shipping regulations.First fully-automated quick disconnectable turret and riser system on a FPSO.
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