Later this fall – on the first of October – commercial production from the Kristen field is due to begin. Located some 240 kilometres off the Norwegian coast in the Halten Bank at depths of 240 to 370 metres, the field boasts extreme conditions: reservoir pressure of 910 bar, with temperatures nearing 170° C. As we go to press, final preparations for the delivery of the semi-submersible platform near completion at Aker Stord south of Bergen, Norway, and over the coming months the platform will assume its place at centre stage.
Located in the south-west part of the Halten Bank, Kristin is the largest of several substantial discoveries made by the former Saga Petroleum company south and west of Statoil’s Åsgard development, and Statoil took over as operator on 1 January 2000. The plan for development and operation (PDO) for the Kristin gas and condensate field in the Norwegian Sea was approved by the Ministry of Petroleum and Energy on 17 December 2001.
Moreover, the Ministry of Petroleum and Energy approved a unitised PDO for three licences on the Halten Bank West in connection with the Kristin development. Production licences 134B, 199 and 257 contain the fields Kristin, Lavrans, Erlend, Morvin (the M prospect) as well as Ragnfrid.
The reservoir lies almost 5,000 metres beneath the seabed, and is due to be drained through 11 subsea wells drilled through four subsea templates, which will be tied back to a floating production platform with a daily production capacity of 126,000 barrels of condensate and just over 18 million cubic metres of rich gas. The 910 bar pressure and 170°C temperature of this reservoir are higher than in any field so far developed off Norway. Lessons learned at Statoil’s Åsgard– the only gas field that comes close in pressure and temperature – have been applied and developed further.
The gas and condensate (light oil) in Kristin, which lie 4,500 to 4,850 metres beneath the seabed, are found in formations dating from 180 to 200 million years ago, the Jurassic period. Recoverable reserves are put at 42 billion cubic metres of gas and 219 million barrels (35 million cubic metres) of condensate. Accounting for 35 billion cubic metres of the total, dry gas contains no liquid components and consists largely of methane with small amounts of ethane and propane. Natural gas liquids – primarily ethane and propane – add up to nine million tons.
The semi-submersible platform near completion at Aker Stord south of Bergen, Norway
Two rigs have been chartered, and the Italian-owned drilling and completion unit Scarabeo 5 spudded its first well in August 2003. West Alpha is the second rig, and a third could be required. Eleven production wells are due to be drilled through four subsea templates. Reservoir conditions on Kristin make special demands on rigs, drilling equipment, personnel and procedures.
The development solution involves coordination with Statoil’s nearby Åsgard field for condensate storage and gas export through the Åsgard Transport pipeline. This integration also involves use of the Kårstø processing complex north of Stavanger and the gas transport network from there to continental Europe. Gassco is operator for the Kårstø gas processing facilities, with Statoil acting as technical service provider.
But the field itself is only the beginning. The semi-submersible rig that will service the field has required an overwhelming amount of planning and co-odination.
All According to Plan
Planning has been essential for the thus-far near-perfect adherence to schedule. According to Statoil’s Bård Heimset, Kristin Project Director and responsible for the semi, “We feel we have really accomplished something with the execution of this project. Aggressive planning of critical activities and standing by those plans has made this project a good model for future activities.” Mr. Heimset attributes this success to the earliest planning stages: “In close co-operation with people from Operations, we took a holistic approach, involving all facets of operations such as drilling and completion.”
And this strategy has paid off. Aker Stord Project Director for the Kristin semi-submersible, Jan-Tore Elverhaug, asserts, “The 6 to 12 month feed period contributed greatly to being able to stick to the schedule, and we’ve very limited carry-over work – a very good basis to stand on. Sufficient lead time allowed us to absorb the challenges.”
Good change control has also been an important success factor in the Kristin project, especially with the global scope of the work being done for the semi-submersible: living quarters with helideck from Sweden, hull from South Korea as well as the riser balcony and flare boom from Spain.
An additional challenge for the plan was that the scope of work includes the engineering and physical preparations on board the platform to prepare the future tie in of the satellite field Tyrihans to Kristin.
Rendering of the Kristin Field
Since Aker Stord received the contract award 11 January 2002, all challenges have been easily absorbed by the forward-looking plan. The first steel plate for Kristing was cut at Aker Stord on 6 January 2003, and the process and utility modules mechanicals were completed 31 March 2004.
Just before the completion, on 28 February, the living quarters arrived by barge from Emtunga in Sweden. The very next day, the riser balcony and flare boom arrived at Aker Stord on the heavy lift vessel Tern and was launched in the fjord. Within a week, 3 March, the Belgian crane barge Rambiz lifted the living quarters on to the utility module. On 8 March, the riser balcony was towed by the Ugland barge and placed near the process module.
Pulling Together the Pieces
On 28 July 2004, the Dockwise heavy lift vessel Mighty Servant 1 arrived at Aker Stord with the steel hull from Samsung Heavy Industries. The 44-day, trouble-free journey via Singapore, the Indian Ocean, the Suez Canal, the Mediterranean and the English Channel, covering a distance of 12,123 nautical miles. Measuring 82 by 82 metres and standing 41 metres high, the roughly 14,450-ton hull was designed by Aker Kvaerner and GVA. After its arrival, the hull was refloated in the fjord near Aker Stord and moored in Aker Stord’s harbour.
Once, the 105 metre-high flare tower lifted onto to the riser balcony on 18 August, the final preparations for mating the main topsides with the substructure began.
Mating the hull and topside took place 30 August, and according to Jan-Tore Elverhaug, “The mating took 1 hour and 42 minutes – that’s close to a record.” After the initial mating, extensive welding was required to attach the two components securely together, with each of the four support columns measuring 18 by 18 metres, and the job was completed on 17 September.
All together, no less than 19,000 tons of modules were installed on the Kristin hull, including the flare boom and riser balcony manufactured at Dragados in Spain, and the living quarters with helideck from Sweden’s Emtunga. By 12 September, the Kristin platform was moored alongside the Maureen quay at Aker Stord, where final qualification and personnel training are now taking place.
Meanwhile, during that same summer, AMC installed 16 suction pile anchors and associated chain and wire moorings on the seabed of the Kristin field.
2005 – A Busy Spring
As agreed to in the original 11 January 2002 contract, the Kristin semi-submersible will begin its journey to the field on 25 March, just after sea trials that will commence 21 March. Aker Stord’s sister company Aker Marine Contractors has been awarded the tow out contract for Kristin, and will connect the semi submersible platform to the pre-installed mooring spread.
At the field await the remaining connections for pipelines and control, and by 1 July the first gas is expected to be onboard the platform. Following this milestone comes final testing
The Secret of Success
Development of Kristin Field, whether considering subsea issues or semi-submersible construction, has been a model for adhering to schedule and dealing with unforeseen challenges. There’s really no secret, just a well designed, well executed plan. Bård Heimset perhaps puts it best: “We maintained full control, and – above all – were loyal to the plan.”
The Statoil-operated gas and condensate field Kristin is located in the south-west part of the Halten Bank. Production starts on 1 October 2005.
Statoil ASA 41.60%
Petoro AS 18.90%
Norsk Hydro Produksjon AS 14.00%
Mobil Development Norway AS 10.50%
Eni Norge AS 9.00%
Total E&P Norge AS 6.00%
The Kristin development project complies with strict HSE requirements. The Environmental Impact Factor (EIF) is introduced to judge the “environmental strain” being caused on the surrounding environment. Hydrogen Sulphid accounts for the major part of the Kristin EIF and zero harmful discharges to sea is made possible through removal of H2S at onshore facilities.