Marginal gas field development
The F3-FA gas field is located approximately 240km north of Den Helder, at a water depth of approximately 40m, within the Dutch sector of the North Sea. The marginal field is operated by Centrica, which holds a 58% working interest in the field.
Current production rate of the field stands at 1.5 million cubic metres per day of gas and 330 cubic metres per day of condensate. The field is estimated to hold 60 billion cubic feet of recoverable reserves and has an estimated production life of eight years.
The gas field was discovered by Nederlandse Aardolie Maatschappij (NAM) in May 1971, with the drilling of the F3-01 well. The field was first appraised by the B18-3 well in February 1982 and was further appraised by the F3-08 well in March that same year.
Venture Production took over the ownership of the field from NAM in March 2008, and initiated the front end engineering and design (FEED) study for the development of the field from April to August 2008, incorporating STP Offshore’s proprietary SIP2 concept. Centrica took over the operatorship of the field from Venture Production in August 2009 and continued the development.
The development plan for the Dutch North Sea field, incorporating a self-installing platform (SIP), was approved in the second half of 2008 and construction works started in April 2009. The first development well, the F3-FA-01 single high-angle well, was drilled in October 2010 using the Noble Scott Marks drilling rig and the field came into production in January 2011.
Compressed gas from the field is exported through a 23km pipeline to the Northern Offshore Gas Transport (NOGAT) pipeline system and further conveyed to the NAM-operated Den Helder plant for processing.
Centrica’s F3-FA SIP, the largest platform of its kind, is designed to operate for around 20 years. It is built to comply with the strict regulations imposed for operations in the Dutch and UK sections of the North Sea. The platform will be transferred to other prospects when production halts from the current field.
The SIP is provided with facilities for separation of gas, condensate and water, and compressing the gas before being exported onshore. It has capacity to treat three million cubic metres of gas per day, 400m³ of condensate and up to 150m³ of water.
The platform’s topside is composed of a cellar deck, a main deck and a top deck. It further features four sub-decks, including a mezzanine deck, an intermediate deck, a heli-deck and a weather deck. The platform provides accommodation facilities for 18 people on the main and intermediate decks.
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The cellar deck is fitted with equipment required for the operation of the platform while the mezzanine deck accommodates the control rooms. The platform can also be remotely operated from Centrica’s J6-A production platform.
The platform is supported by four tubular legs, which are further supported by four huge suction piles on the seabed. The platform was attached to the legs with 16 M240 superbolts, 16 studs of around five metres and 16 special locknuts, using the cup and ball bearing method.
The platform is designed to drill three wells through one of its 3.25m-diameter tubular legs. A ten-inch gas export riser passes out through one of the other legs, which is also equipped with a ten-inch riser for possible future imports. The pressure required to transport the gas from the field is provided by a Solar Centaur 40 compressor turbine.
Two gas-fuelled generators with a capacity of 347kW each and a 500kW back-up diesel generator provide the required power to operate the platform.
Safety equipment onboard the platform includes a diesel hydraulic fire pump, an electrically driven fire water pump and a free-fall lifeboat with capacity for 32 people.
Centrica’s F3-FA SIP’s topside weighs 4,000t and is 30m-long, 50m-wide and 30m-high. Each of the platform’s suction piles is 13m-long, has a diameter of 15m and weighs 400t. The platform’s legs are 75m-long, have a diameter of 3.5m and weigh 375t each. The stiffening frames weigh 425t each, while the overall weight of the platform is 9,500t.
The platform was installed employing the Boa 35 transportation barge, three tugs and a diving support vessel (DSV). Installation works were completed in September 2010.
The engineering, procurement, construction and installation (EPCI) contract for the platform was awarded to Heerema Fabrication Group (HFG). The company further subcontracted Iv-Oil & Gas to design the structure and topside process and procure tagged equipment, while SPT Offshore was subcontracted to design and fabricate the platform’s suction piles, as well as initiate the transport and installation operation.
Orca Offshore performed the transport and installation analysis for the platform, which involved motion and stability analysis, multi-body dynamic analysis, structural spectral analysis and scale model tests. The company employed Bentley’s MOSES model for calculating the transport forces.
Volker InfraDesign and NPM also took part in the platform installation. The bolted joints for the platform were supplied by Safe Tensioning System (STS).
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