Snøhvit Gas Field, Barents Sea, Norway

The Snøhvit development comprises three fields – Snøhvit, Albatross and Askeladd. These lie in the Barents Sea, about 140km north-west of Hammerfest in northern Norway. The fields were discovered in 1984 in 250m to 345m of water and extend across seven production licences.

Snøhvit is operated by Statoil on behalf of Petoro, TotalFinaElf, Gaz de France, Norsk Hydro, Amerada Hess, RWE Dea and Svenska Petroleum Exploration.

All primarily contain natural gas with small quantities of condensate. The accumulation exceeds 193 billion cubic metres of natural gas and 113 million barrels of condensate.

A development plan was proposed in 1991, but was halted on economic grounds. Statoil submitted a plan for development and operation of the field in September 2001 that was approved in March 2002. It will be developed by a total of 21 wells.

Snøhvit will be the first major development on the Norwegian continental shelf without a fixed or floating unit. Instead, a subsea production system on the seabed will feed a land-based plant on the north-western coast of Melkøya, at the entrance to the shipping channel into Hammerfest via a 68cm ID, 160km gas pipeline. In addition come two chemical lines, an umbilical and a separate pipeline for transporting carbon dioxide, which will be laid in the summer of 2005.

Both the subsea production system located on the field and pipeline transport will be monitored and controlled from a control room at Melkøya, where operators will be able to open and close valves on the seabed 140km away with signals transmitted along fibre-optic cables, and with high-voltage electrical and hydraulic power lines.

The potential routes for the pipelines and cables have been mapped, as well as the areas where the subsea installations are to be sited in order to ensure the most favourable location for pipelines and equipment.

The work was carried out from the Normand Tonjer, which was followed by geotechnical surveys on the field and along the pipeline routes by the ship Bucentaur.

CARBON CAPTURE STORAGE

In April 2008, Statoil announced carbon storage had started on its Snøhvit field – Statoil is reinjecting Snøhvit's CO2 emissions into the ground beneath the gas-bearing formation on the field. The process will reduce CO2 emissions by 700,000t a year when Snøhvit is at full capacity, it is estimated. This is the equivalent of emissions from 280,000 cars.

Natural gas is first pumped to a carbon capture plan at Melkøya. Here, 5% to 8% of CO2 is removed from the gas and piped back to a 2,600m-deep sandstone formation at Snøhvit, where it sits under the seabed.

GAS LIQUEFACTION

The unprocessed wellstream arriving at Melkøya is separated and the gas cooled down to liquid form and exported. The carbon dioxide is separated out at the land plant and returned in a separate line for storage underground beneath the seabed.

A liquefaction plant will reduce its volume 600-fold by decreasing its temperature to -163ºC. This will be carried out on a gas liquefaction barge, being built at the Spanish shipyard group Izar Construcciones Naval's yard in Ferrol in a contract worth about NKr170m. The barge will measure 9m high by 154m long and 54m wide.

The chosen building approach greatly reduces the need for steelwork on Melkøya, and gives cost savings as well as higher productivity compared with constructing the plant on site.

Following completion, the barge will be towed to an outfitting yard where about 24,000t of process equipment for the gas liquefaction plant will be installed on its deck. From there, it will then be transported to Melkøya on a heavy-lift ship and installed in a dock blasted out in advance. About 70 cargos of LNG a year will be shipped out from Melkøya.

The annual exports are anticipated to be 5.75 billion cubic metres of LNG, 747,000t of condensate and 247,000t of Liquefied Petroleum Gases (LPG). There are long-term contracts with Iberdrola in Spain and El Paso in the USA. The total investment will include NKr34.2bn for field development, pipeline and land plant and NKr5.4bn for ships. Snøhvit will start production in 2006.