Located on Haltenbanken in the Norwegian Sea, the Tyrihans field is situated on Norwegian Blocks 6406/3 and 6407/1 in water measuring 886 feet (270 meters). Statoil is the operator of the field and owns a 58.8% interest; Total owns 23.18%; Eni owns 6.23; and ExxonMobil owns 11.75%.

With development costs totaling US $1.8 billion (NOK 12.8 billion), Tyrihans is the largest development brought on stream by Statoil in 2009. The field's reservoir, about 11,486 feet (3,500 meters) deep in the Garn formation, holds estimated recoverable resources of 811 MMbo and 1.24 Tcf of gas.

Tyrihans commenced production on July 8, 2009 and has a life expectancy of 20 years. The field is expected to reach a plateau production of 459 MMcf/d (13 MMcm/d) and a plateau production for liquid at 459,091 cf/d (13,000 cm/d).

Drilling

Two discoveries defined the Tyrihans field. In 1983, the first well, 6407/1-2 Tyrihans Sor, encountered an oil column with a condensate-rich gas cap; and the second well 6407/1-3 Tyrihans Nord, intersected gas condensate with an underlying oil column.

The Transocean Arctic semisub, contracted by Statoil for a multi-year term in 2005, arrived at the field to commence development drilling in April 2008. The semisub's drilling program encompassed the drilling and completion of 11 wells, seven of which are multilateral (multiple trajectories in the reservoir for maximum oil recovery). In 2015, a gas production well is planned to be drilled, bringing the total amount of wells to 12.

Subsea and Platforms

Government approval for field development was received on Feb. 16, 2006. Five subsea templates -- four for production and gas injection, and one for water injection –- developed the field. With a total of 12 wells (eight oil producers, one gas producer, two gas injectors and one water injector) to be drilled on the Tyrihans field, seven of the wells have several trajectories in the reservoir for maximized oil recovery.

FMC Technologies signed a contract at a value of $216 million (NOK 8.6 billion) for the supply of subsea systems, which included 13 subsea trees, five template structures with manifolds, a topside control system and work-over systems.

In order to increase the recovery of the reservoir, two subsea pumps will inject 500,000 cf (14,000 cm) of untreated seawater into the wells for pressure maintenance. The pumps are expected to boost oil production by 10%. Aker Kvaerner received the contract, worth $28 million (NOK 200 million), for the delivery and installation of the subsea pumps. Along with seawater, gas will also be injected into the reservoir.

The subsea installation and the gas injection are all tied-back to the Kristin and Asgard B floating platforms. The semi-submersible production platform, Kristin, is an existing platform located on the Kristin field, roughly 22 miles (35 kilometers) away from Tyrihans. The floating Asgard B gas platform, also an exiting facility, is located 16 miles (25 kilometers) southeast of Tyrihans on the Asgard field.

Kristin underwent modifications and alterations, such as a newly constructed 276-ton (250-tonne) process module that was installed on the platform in 2008. Asgard B was also modified and upgraded in order to provide pressure support to the Tyrihans field.

Pipeline

Production from Tyrihans' seabed templates is sent to the Kristin platform via a 27-mile (43-kilometer), 16-to-18-inch-diameter pipeline with a 52 kV heating cable. Also, a 10-inch-diameter carbon steel pipeline sends pressure support, in the form of gas injection from the Asgard B platform to the Kristin platform. Oil and condensate is stabilized with liquid production from Kristin, and then sent by pipeline to the Asgard C storage vessel, and finally exported by shuttle tankers.

The German company, Butting, received a contract worth $42 million (NOK 300 million) to deliver and install the steel pipe for the pipeline. The pipe was delivered in December 2006 and laid in 2007. The Danish company, Ramboll, provided the engineering work for the pipelines and its routes.

Direct Electrical Heating (DEH) will be used to insulate the pipeline and prevent freezing in case of production shutdowns. The DEH system has an armored feeder cable, installed parallel to the pipeline, and a piggyback cable installed on the pipeline.