Glitne, North Sea Northern, Norway

Glitne lies in block 15/5 and 15/6 in the Sleipner area of the Norwegian sector of the North Sea about 40km north-west of the Sleipner East development. The production licence for the development, 048, was awarded to Statoil in 1977. Statoil owns 58.9% of Glitne; Total E&P Norge AS 21.8%; Det Norske Oljeselskap (DNO) 10.0% and Dansk Olie-og Naturgas (DONG) Norge 9.3%.

Glitne, at a water depth of 110m (361ft), is a Palaeocene reservoir with a gas / oil ratio of 50m³:m³. The reservoir consists of several separate sand sheets of deep-marine fan deposits in the upper Heimdal formation.

The reservoir contains 25 million barrels of recoverable oil and was initially due to produce over 26 months, at an estimated maximum daily flow of some 40,000 barrels for the first 15 months (this initial life has now been superceded).

The total investment in the project has been estimated to be NKr700m ($90m).

DRILLING

The field was discovered in 1955 with well 15/5-5 and it was appraised by well 15/5-6 in 1997. Well 15/5-3 determined the edge of the field and found the oil / water contact.

Glitne has been developed by five production wells, located immediately below the floating production system, as well as one water injection well located 2km-3km away and a gas injection well. The water-injector well was drilled vertically to a depth of 2,000km. The development wells all use horizontal wells with 800m-1,000m horizontal sections.

DEVELOPMENT

In June 2000, Petroleum Geo-Services entered into an agreement with Statoil to produce the Glitne field until 2005. This was later extended so that the field would be in operation until late 2007. PGS have produced this field with its Floating Production, Storage and Offloading (FPSO) vessel, Petrojarl 1, owned by Teekay Petrojarl Production ASA.

PETROJARL 1

Petrojarl 1, a Tentech 685 turret-moored FPSO, was built in 1986 in the NKK shipyard. It is a Norwegian-flagged vessel, with the DNV classification DNV+AI mobile offshore Unit. It was designed by Golar Nor and features a non-disconnectable internal turret secured by eight anchor legs.

Oil is transferred by a passive single-path swivel. The wells are connected to the Petrojarl 1 with a total of seven flexible risers (the ship has reception slots to accommodate eight risers). Control systems include a Simrad positioning system and an Allan Bradley automation system.

The FPSO has an overall length of 209m and a breadth of 32m. The vessel depth is 18m and the maximum draught is 13m. Its tonnage is 31,473dwt and it has a transit speed of 10kt.

It is powered by two dual-fuel boilers connected to four 2.8MW dual-fuel turbines. There are also two 1.5MW diesel engines. The FPSO is propelled by twin propellers.

It has 68 berths and an operating crew of 43 (36 regular PGS production crew and one representative of Statoil). There are also three cranes with a ranting of 30t and 20m.

The FPSO has a maximum oil-production rate of 45,000bpd and a maximum gas-production rate of 30mcft/d. It can flare a full 30mcft/d, if necessary.

It has gas compression facilities of 20mcft/d and can treat 32,000 barrels of water a day in hydrocyclones, with a maximum oil discharge of 40ppm. From early 2003 water was reinjected into the reservoir using ship facilities. Waste from the platform is shipped to the Statoil Dusavik shore base for treatment and disposal.

Petrojarl 1 can store 188,000 barrels of crude oil in its tanks and its slop tanks have a capacity of 7,000 barrels.The tanker Petroskald ships the production from the FPSO every fifth day usually to the ports of Rotterdam of Kalundborg.

The mooring system consists of eight 3.3in chains and each line is linked to a 15t Stevpris anchor. There are also two 1,600kW thrusters aft and two 1,600kW thrusters fore.

SUBSEA

The five subsea wells use Christmas trees that were first used in the Tommeliten field. These were removed and refurbished and then installed as single satellite wells within 80m-100m of each other.

The project has also involved an upgrading of the gas and water-injection system on-board the FSPO. Gas is injected into one of the water-injection wells (now a gas injection well) to obviate flaring.

The field first came on-stream at the end of August 2001. It originally had an estimated production life of two to three years, depending on the economics of oil price trends.

Production in the second full year of operation (2003) amounted to 10.6 million barrels, or approximately 29,000bpd, which was 12% more than the expected production total for the year. Production is now continuing into 2007 and the license for the field is valid until February 2013.

NEW DEVELOPMENT

In August 2007 the Norwegian Petroleum Safety Authority approved Statoil's new plan to deploy the 'Ocean Vanguard' on the Glitne Field development in the North Sea. This semi-submersible rig is due to drill and complete well 15/5-A-7-H as an oil producer under an eight-week drilling programme.

The new well is part of an ongoing campaign to improve recovery from the field, and to extend its productive life-span. An additional well is also under consideration for the near future.

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