The Norne Production Ship - Design Considerations

ABSTRACT The Norne Production and Storage Vessel (PSV) will be the largest monohull production facility in the world with a throughput capacity of 173,000 bbl oil and 238 mill scf gas per day, Production will be based on subsea completed wells, drilled through five templates and connectedto the turret moored PSV via flexible rises and flowlines. A high capacity swivel stack has been designed fortransfer of oil/gas/water between turret and facilities on the process deck. The Norne field is located further north than any other Norwegian field in operation or under development, and the water depth on location is 380 m. INTRODUCTION The Norne field is located in Block 6608/1 O, about 200 km west of the mid-Norway coast. The water depth on location is about 380 m. The top of the reservoir is found at a depth of 2525 m below MSL. At a reference depth of 2639 m the formation pressure is 273 bar and the temperature 98 degrees C. The recoverable oil reserves are about 72 mill. Sm3. The reservoir drive mechanism will be a combination of water and gas injection. Initially all produced gas will be reinjected into the gas cap. The plateau production rate representing a yearly recovery rate of 12.57. of total recoverable reserves Will be maintained for 3-4 years. The field will produce forabout 16 years. The development scenario is based on a Production and Storage Vessel (PSV) in combination with a subsea production system comprising 6 oil producers, 6 water injectorsand 2 gas injectors. The wells will be drilled through five subsea templates, two located in the northern part and three in the southern part of the field. The templates will be connected to the PSV via flexible flowlines and risers. THE PRODUCTION AND STORAGE VESSEL The PSV is a turret moored, ship-shaped production, storage and offloading vessel of Tentech 850 S design, see Fig.1. With throughput capacities as listed below the Nome PSV will be the largest monohull production system in the world. (Available In Full Paper) The vessel will, on location, be moored by means of a 12 point mooring system with 12 anchor chain winches arranged on the turret of the vessel. Five fully azimuthing, variable speed thrusters will be utilized as an active element in the station keeping and heading control, see section Instrumentation and control. The turret which will be held geostationary by the mooring lines, will also serve as attachment for all the flexible risers. From the swivel, on top of the turret, {he well stream is transferred to the inlet separator on the process deck. A total of 16 storage tanks and 2 slop tanks with a total capacity of 117,000 m3 will be arranged in the hull. Double bottom tanks, wing tanks and peak tanks provide ample capacity (about 48,000 m3) to maintain sufficient draught in ballast condition. All water ballast tanks and systems are segregated from the oil storage tanks. Accommodation for 120 persons will be arranged in the forward part of the vessels.